Dietary Intake of ω-6 and ω-3 Fatty Acids and Risk of Colorectal Cancer in a Prospective Cohort of U.S. Men and Women

Associations between diet and nutritional supplements and colorectal cancer: A systematic review

Background and Aim

Colorectal cancer (CRC) is one of the most prevalent cancers around the world. The link between nutrients and the likelihood of developing CRC remains uncertain. The primary objective of the present study was to investigate the potential connection between dietary intake/dietary supplements and the occurrence of CRC through a literature review.

Methods

A comprehensive online search was conducted in PubMed, Scopus, Web of Science, and the Cochrane Library from January 1990 to March 2023 using appropriate keywords. A systematic search was conducted for clinical trials and cohort studies in order to determine the relationship between dietary components/supplements and CRC.

Results

The intake of long-chain n-3 polyunsaturated fatty acids (n-3 LCPUFAs), consisting of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has the potential to decrease the likelihood of developing CRC (eight studies found positive effects and four studies found no association). Some other dietary components such as probiotics, prebiotics, and synbiotics may contribute to suppressing CRC development (three studies found positive effects, whereas three studies did not find any association). There is inconclusive evidence that supplementation with certain micronutrients including vitamin D (one trial found positive effects and another trial reported no association), folate, zinc, and selenium may reduce the risk of CRC.

Conclusion

Some dietary supplements such as n-3 LCPUFAs and probiotics have the potential to reduce the risk of developing CRC. Further studies are necessary to validate these results and understand the underlying mechanisms.

Role of dietary intake of specific polyunsaturated fatty acids (PUFAs) on colorectal cancer risk in Iran

High-fat diets have been associated with colorectal cancer (CRC) risk, and the role of polyunsaturated fatty acids (PUFAs) has been reported to vary based on the length of PUFAs. We explored the association between dietary omega-6 and omega-3 PUFAs intake and CRC. We analyzed 865 CRC patients and 3206 controls from a case-control study of Iran (IROPICAN study). We used multivariate logistic regression models to calculate the odds ratios (OR) and 95% confidence intervals (CI) for the association between PUFAs intake and CRC risk. Our results showed that gamma-linolenic acid (18:3 n-6, GLA), arachidonic acid (20:4n-6, ARA), a-linolenic acid (Cis-18:3n-3, ALA), eicosapentaenoic acid (20:5n-3, EPA), docosahexaenoic acid (22:6n-3, DHA) consumption was not associated with the risk of CRC. However, the OR of linoleic acid (18: 2n-6, LA) intake was 1.47 (95% CI 1.01-2.14, p = 0.04) for proximal colon and that of docosapentaenoic acid (22:5n-3, DPA) intake was 1.33 (95% CI 1.05-1.69, p = 0.01) for rectum. This study indicates a high level of LA is associated with an increased risk of proximal colon cancer, and DPA intake was positively associated with rectum cancer risk. Furthermore, our study noted a high intake of n-6 (from vegetable oils) compared to n-3 PUFAs (from fish and seafood) in this population. Public awareness and government support is needed to increase fish and seafood production and consumption in Iran.

Metabolomics of head and neck cancer in biofluids: an integrative systematic review

INTRODUCTION

Head and neck cancer (HNC) is the fifth most common cancer globally. Diagnosis at early stages are critical to reduce mortality and improve functional and esthetic outcomes associated with HNC. Metabolomics is a promising approach for discovery of biomarkers and metabolic pathways for risk assessment and early detection of HNC.

OBJECTIVES

To summarize and consolidate the available evidence on metabolomics and HNC in plasma/serum, saliva, and urine.

METHODS

A systematic search of experimental research was executed using PubMed and Web of Science. Available data on areas under the curve was extracted. Metabolic pathway enrichment analysis were performed to identify metabolic pathways altered in HNC. Fifty-four studies were eligible for data extraction (33 performed in plasma/serum, 15 in saliva and 6 in urine).

RESULTS

Metabolites with high discriminatory performance for detection of HNC included single metabolites and combination panels of several lysoPCs, pyroglutamate, glutamic acid, glucose, tartronic acid, arachidonic acid, norvaline, linoleic acid, propionate, acetone, acetate, choline, glutamate and others. The glucose-alanine cycle and the urea cycle were the most altered pathways in HNC, among other pathways (i.e. gluconeogenesis, glycine and serine metabolism, alanine metabolism, etc.). Specific metabolites that can potentially serve as complementary less- or non-invasive biomarkers, as well as metabolic pathways integrating the data from the available studies, are presented.

CONCLUSION

The present work highlights utility of metabolite-based biomarkers for risk assessment, early detection, and prognostication of HNC, as well as facilitates incorporation of available metabolomics studies into multi-omics data integration and big data analytics for personalized health.

CYP eicosanoid pathway mediates colon cancer-promoting effects of dietary linoleic acid

Human and animal studies support that consuming a high level of linoleic acid (LA, 18:2ω-6), an essential fatty acid and key component of the human diet, increases the risk of colon cancer. However, results from human studies have been inconsistent, making it challenging to establish dietary recommendations for optimal LA intake. Given the importance of LA in the human diet, it is crucial to better understand the molecular mechanisms underlying its potential colon cancer-promoting effects. Using LC-MS/MS-based targeted lipidomics, we find that the cytochrome P450 (CYP) monooxygenase pathway is a major pathway for LA metabolism in vivo. Furthermore, CYP monooxygenase is required for the colon cancer-promoting effects of LA, since the LA-rich diet fails to exacerbate colon cancer in CYP monooxygenase-deficient mice. Finally, CYP monooxygenase mediates the pro-cancer effects of LA by converting LA to epoxy octadecenoic acids (EpOMEs), which have potent effects on promoting colon tumorigenesis via gut microbiota-dependent mechanisms. Overall, these results support that CYP monooxygenase-mediated conversion of LA to EpOMEs plays a crucial role in the health effects of LA, establishing a unique mechanistic link between dietary fatty acid intake and cancer risk. These results could help in developing more effective dietary guidelines for optimal LA intake and identifying subpopulations that may be especially vulnerable to LA's negative effects.

Comprehensive Investigation on Associations between Dietary Intake and Blood Levels of Fatty Acids and Colorectal Cancer Risk

BACKGROUND

Increasingly, studies have discovered that different fatty acids (Fas) are linked to colorectal cancer (CRC) risk.

METHODS

We systematically searched Embase and Medline databases to identify eligible studies that examined the associations of different types of Fas with CRC risk. The effect estimates and their 95% confidence intervals (Cis) were pooled using a random-effects model. Subgroup and sensitivity analyses were performed to examine the robustness of the study findings.

RESULTS

This study evaluated the associations of 28 dietary and 18 blood Fas with CRC risk by summarizing the most updated evidence from 54 observational and four Mendelian Randomization (MR) studies. The present findings suggested that high dietary intake of eicosapentaenoic acid (EPA), docosahexanoic acid (DHA), and docosapentaenoic acid (DPA) are related to low risk of CRC, while the n-6/n-3 PUFA ratio and trans-FA are related to high risk of CRC. The summary of all cohort studies found that a high intake of SFA and DHA was a protective factor for CRC, and a high intake of the n-6/n-3 PUFA ratio was a risk factor for CRC. In the subgroup analysis of cancer subsites, we found that the dietary intake of linoleic acid (LA) and trans-FA are risk factors, while DPA is a protective factor for colon cancer. High dietary DHA intake was associated with a lower risk of rectal cancer, while the dietary n-6/n-3 PUFA ratio was associated with a higher risk of rectal cancer. Meta-analysis of blood FA levels showed a significant reverse association between blood pentadecanoic acid and CRC risk, whilst other blood Fas showed no significant association with CRC risk. All included MR studies showed that high plasma arachidonic acid (AA) is associated with increased CRC risk.

CONCLUSIONS

Current evidence on the dietary intake and blood levels of Fas in relation to CRC risk is less consistent. Future studies are needed to investigate how the metabolism of Fas contributes to CRC development.

Association between dietary intake of n-3 polyunsaturated fatty acids and risk of colorectal cancer in the Japanese population: The Japan Collaborative Cohort Study

BACKGROUND

Epidemiological studies of the dietary intake of specific n-3 polyunsaturated fatty acids (PUFA) and anatomical subsite-specific colorectal cancer (CRC) are limited. We examined the prospective associations of total n-3 PUFA, marine-derived n-3 PUFA [combined eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA)], and alpha-linolenic acid (ALA) as plant-derived n-3 PUFA with the risk of CRC by subsite in the Japan Collaborative Cohort Study.

METHODS

The participants completed a self-administered food frequency questionnaire and had no prior history of CRC. Cox proportional hazards model was used to determine the associations between n-3 PUFAs intake and CRC risk overall and by anatomical subsite.

RESULTS

During the median 13.8-year follow-up period, 699 of the 42,536 participants aged 40-79 years developed incident CRC. An inverse association was found between dietary ALA intake and the risk of distal colon cancer; the multivariable hazard ratios and 95% confidence intervals for the highest quartiles (Q4) were 0.41 (0.21-0.81; p trend = 0.01) compared with the lowest quartiles (Q1). Marine n-3 PUFA intake was not associated with CRC risk in the overall or anatomical subsite-specific analyses.

CONCLUSION

Our findings suggest that higher ALA intake may be beneficial for lowering the risk of distal colon cancer.

Association between Dietary Fatty Acid Patterns and Colorectal Cancer Risk: A Large-Scale Case-Control Study in China

Associations of dietary fatty acids with the risk of colorectal cancer (CRC) remain controversial. The objective of this study was to examine whether dietary-derived fatty acid patterns were related to CRC risk among Chinese people. A total of 2806 CRC patients and 2806 frequency-matched controls were interviewed in this case-control study between July 2010 and May 2021. A food frequency questionnaire was used to gather information on dietary intake. Four fatty acid patterns were identified using factor analysis. The even-long-chain fatty acid pattern had no statistically significant association with CRC risk (adjusted Odds ratio (aOR), 1.16; 95% confidence interval (CI), 0.97-1.39; ptrend = 0.129). However, significant inverse associations were found between the medium-chain and long-chain saturated fatty acid (SFA) pattern (aOR, 0.34; 95%CI, 0.27-0.42), the highly unsaturated fatty acid pattern (aOR, 0.73; 95%CI, 0.60-0.88), the odd-chain fatty acid pattern (aOR, 0.69; 95%CI, 0.57-0.83), and CRC risk. The interaction between fatty acid patterns and sex was observed, and the association between the highly unsaturated fatty acid pattern and CRC risk differed by subsite. In conclusion, increasing the intakes of foods rich in medium-chain SFAs, highly unsaturated fatty acids, and odd-chain fatty acids may be related to a lower risk of CRC.

Association of Dietary Intake and Biomarker of α-Linolenic Acid With Incident Colorectal Cancer: A Dose-Response Meta-Analysis of Prospective Cohort Studies

Background and Objective

There is keen interest in better understanding the impacts of alpha-linolenic acid (ALA), a plant-derived n-3 fatty acid, in ameliorating the development of cancer; however, results of several prospective cohorts present an inconsistent association between ALA intake and the incident colorectal cancer (CRC). We aimed to investigate the summary association of dietary intake and biomarkers of ALA with CRC risk based on the prospective cohorts.

Methods

Pertinent prospective cohorts were identified in Cochrane Library, PubMed, and EMBASE from inception to February 2022. Study-specific risk ratios (RRs) with 95% confidence intervals (CIs) for comparing the top with the bottom quartiles of ALA levels were combined using a random-effects model. Nonlinear dose-response relationships of ALA levels in diet and blood with CRC risk were assessed using the restricted cubic spline models, respectively.

Results

Over the duration of follow-up with a median of 9.3 years ranging from 1 to 28 years, 12,239 CRC cases occurred among 861,725 participants from 15 cohorts (11 studies on diet and 5 studies on biomarkers including 4 on blood and 1 on adipose tissue). The summary RR was 1.03 (95% CI: 0.97, 1.10; I²: 0.00%) for dietary intake and 0.83 (95% CI: 0.69, 0.99; I²: 0.00%) for biomarker. Each 0.1% increase in the levels of ALA in blood was associated with a 10% reduction in risk of CRC (summary RR: 0.90, 95% CI: 0.80, 0.99; I²: 38.60%), whereas no significant dose-response association was found between dietary intake of ALA and the incident CRC (p for non-linearity = 0.18; p for linearity = 0.24).

Conclusions

Blood levels of ALA were inversely and linearly associated with the risk of CRC, which suggested that increased intake of ALA to improve circulating levels was beneficial for CRC prevention.

Comparative Effects of Traditional Versus Genetically Modified Soybean Oils on Colon Tumorigenesis in Mice

Soybean oil, which has high abundance of linoleic acid (LA, 18:2ω-6), is the most commonly consumed edible oil. Recent studies support that a high dietary intake of LA is linked with increased risks of developing colonic inflammation and colon cancer. Here we studied the effects of the genetically modified Plenish^® soybean oil, which has low abundance of LA as well as α-linolenic acid (ALA, 18:3ω-3), on development of azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colon tumorigenesis in mice. Compared with a diet rich in traditional soybean oil, administration of a diet enriched with the Plenish oil has little impact on AOM/DSS-induced colon tumorigenesis, colonic infiltration of immune cells, expressions of inflammatory genes, and tumor markers. These results suggest that the traditional and the Plenish soybean oils have similar effects on development of AOM/DSS-induced colon cancer in mice.

Roles of Lipid Peroxidation-Derived Electrophiles in Pathogenesis of Colonic Inflammation and Colon Cancer

Redox stress is a common feature of gut disorders such as colonic inflammation (inflammatory bowel disease or IBD) and colorectal cancer (CRC). This leads to increased colonic formation of lipid-derived electrophiles (LDEs) such as 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), trans, trans-2,4-decadienal (tt-DDE), and epoxyketooctadecenoic acid (EKODE). Recent research by us and others support that treatment with LDEs increases the severity of colitis and exacerbates the development of colon tumorigenesis in vitro and in vivo, supporting a critical role of these compounds in the pathogenesis of IBD and CRC. In this review, we will discuss the effects and mechanisms of LDEs on development of IBD and CRC and lifestyle factors, which could potentially affect tissue levels of LDEs to regulate IBD and CRC development.

Alterations of the Muscular Fatty Acid Composition and Serum Metabolome in Bama Xiang Mini-Pigs Exposed to Dietary Beta-Hydroxy Beta-Methyl Butyrate

Simple Summary

Pork is the most consumed meat source for humans, and the utilization of nutritional approaches to produce pork with an appropriate content of intramuscular fat (IMF) and a balanced ratio of different kinds of fatty acid is an important objective pursuit of swine production. We speculated that dietary supplementation of beta-hydroxy beta-methyl butyrate (HMB) may provide benefits in lipid metabolism of skeletal muscle. In this study, we try to investigate the effects of dietary HMB supplementation on muscular lipid metabolism in Bama Xiang mini-pigs. We found that HMB supplementation could decrease the IMF content and increase n3 polyunsaturated fatty acids as well as regulate the related metabolites (N-Methyl-l-glutamate and nummularine A) in the serum of Bama Xiang mini-pigs, thus improving their meat quality.

Abstract

This study aimed to investigate the effects of dietary beta-hydroxy beta-methyl butyrate (HMB) supplementation on muscular lipid metabolism in Bama Xiang mini-pigs. Thirty-two piglets (8.58 ± 0.40 kg, barrow) were selected and fed a basal diet supplemented either with 0 (control), 0.13%, 0.64%, or 1.28% HMB for 60 days. Throughout the experiments, they had free access to clean drinking water and diets. Data of this study were analyzed by one-way ANOVA using the SAS 8.2 software package, followed by a Tukey’s studentized range test to explore treatment effects. The results showed that compared to the control, 0.13% HMB decreased the intramuscular fat (IMF) content and increased polyunsaturated fatty acids (PUFAs) in Longissimus thoracis muscle (LTM), and increased the n3 PUFAs in soleus muscles (SM, p < 0.05). Moreover, HMB supplementation led to alterations in the mRNA expression of genes related to lipid metabolism. Serum metabolome profiling showed that in both LTM and SM of Bama Xiang mini-pigs, N-Methyl-l-glutamate was positively correlated with SFA and nummularine A was negatively correlated with C18:3n3 PUFA (p < 0.05). Therefore, N-Methyl-l-glutamate and nummularine A might be potential biomarkers of the HMB-supplemented group. These results suggested that dietary HMB supplementation could decrease the IMF content and increase n3 PUFAs as well as regulate the related metabolites (N-Methyl-l-glutamate and nummularine A) in the serum of pigs.

Maternal DHA supplementation influences sex-specific disruption of placental gene expression following early prenatal stress

Early life adversity is widely recognized as a key risk factor for early developmental perturbations and contributes to the presentation of neuropsychiatric disorders in adulthood. Neurodevelopmental disorders exhibit a strong sex bias in susceptibility, presentation, onset, and severity, although the underlying mechanisms conferring vulnerability are not well understood. Environmental perturbations during pregnancy, such as malnutrition or stress, have been associated with sex-specific reprogramming that contribute to increased disease risk in adulthood, whereby stress and nutritional insufficiency may be additive and further exacerbate poor offspring outcomes. To determine whether maternal supplementation of docosahexanoic acid (DHA) exerts an effect on offspring outcome following exposure to early prenatal stress (EPS), dams were fed a purified 10:1 omega-6/omega-3 diet supplemented with either 1.0% preformed DHA/kg feed weight (DHA-enriched) or no additional DHA (denoted as the control diet, CTL). Dams were administered chronic variable stress during the first week of pregnancy (embryonic day, E0.5–7.5), and developmental milestones were assessed at E 12.5. Exposure to early prenatal stress (EPS) decreased placenta and embryo weight in males, but not females, exposed to the CTL diet. DHA enrichment reversed the sex-specific decrease in placenta and embryo weight following EPS. Early prenatal exposure upregulated expression of genes associated with oxygen and nutrient transport, including hypoxia inducible factor 3α (HIF3α), peroxisome proliferator-activated receptor alpha (PPARα), and insulin-like growth binding factor 1 (IGFBP1), in the placenta of CTL diet males exposed to EPS. DHA enrichment in EPS-exposed animals abrogated the male-specific upregulation of PPARα, HIF3α, and IGFBP1. Taken together, these studies suggest that maternal dietary DHA enrichment may buffer against maternal stress programming of sex-specific outcomes during early development.

Dietary fatty acids and colorectal cancer risk in men: A report from the Shanghai Men's Health Study and a meta-analysis

Evidence from animal models suggests that dietary fatty acids have both anticancer and tumor-promoting effects. Whether dietary fatty acids are associated with colorectal cancer (CRC) in humans remains inconclusive. We investigated associations between dietary fatty acids and risk of CRC among 59 986 men who participated in the Shanghai Men's Health Study (SMHS), an ongoing population-based prospective cohort study. We identified 876 incident CRC cases in the SMHS during a mean follow-up of 9.8 years. Associations between dietary fatty acid intake and CRC risk were evaluated by Cox proportional hazard regression analyses. Consumption of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) was not significantly associated with CRC risk. Multivariate hazard ratios (HRs) and respective 95% confidence intervals (CIs) for Quartile 4 vs Quartile 1 were 0.92 (0.74-1.14; Ptrend = 0.47) for SFA, 0.95 (0.79-1.16; Ptrend = 0.74) for MUFA and 1.18 (0.95-1.46; Ptrend = 0.21) for PUFA. No significant associations were found for total n-6 PUFA or total n-3 PUFA. Additionally, we performed a meta-analysis to summarize results from the present study and 28 reports from 26 additional cohorts, which supported the overall null association between dietary fatty acid intake and CRC risk among men. Docosahexanoic acid and eicosapentaenoic acid were associated with 11% to 12% reduced risk, and linoleic acid a 19% increased risk, of CRC in the meta-analysis of combined sexes. In conclusion, this population-based prospective study and meta-analysis of cohort studies found little evidence that dietary fatty acid intake was associated with risk of CRC in men.

Dual Behavior of Long-Chain Fatty Acids and Their Cyclooxygenase/Lipoxygenase Metabolites on Human Intestinal Caco-2 Cell Growth

Etiology of colorectal cancer (CRC) is related, at least in part, with nutritional profile and epidemiological data indicating a key role of dietary fat on CRC pathogenesis. Moreover, inflammation and eicosanoids produced from arachidonic acid might have a pivotal role in CRC development. However, the effect of specific fatty acids (FAs) on intestinal epithelial cell growth is not completely studied now. By this reason, the aim of this work is to unravel the effect of different saturated and unsaturated long-chain fatty acids (LCFA) and some LCFA metabolites on CRC cell line growth and their possible mechanisms of action. Our results demonstrated that oleic acid is a potent mitogenic factor to Caco-2 cells, at least in part, through 10-hydroxy-8-octadecenoic synthesized by lipoxigenase pathway, whereas polyunsaturated FAs such as eicosapentaenoic (EPA) acid has a dual behavior effect depending on its concentration. A high concentration, EPA induced apoptosis through intrinsic pathway, whereas at low concentration induced cell proliferation that could be related to the synthesis of eicosanoids such as prostaglandin E₃ and 12-hydroxyeicosapentaenoic acid and the subsequent induction of mitogenic cell signaling pathways (ERK 1/2, CREB, p38α). Thus, this study contributes to understand the complicated relationship between fat ingest and CRC.

N-6 Polyunsaturated Fatty Acids and Risk of Cancer: Accumulating Evidence from Prospective Studies

Previous studies on the association between polyunsaturated fatty acids (PUFAs) and cancer have focused on n-3 PUFAs. To investigate the association between intake or blood levels of n-6 PUFAs and cancer, we searched the PubMed and Embase databases up to March 2020 and conducted a meta-analysis. A total of 70 articles were identified. High blood levels of n-6 PUFAs were associated with an 8% lower risk of all cancers (relative risk (RR) = 0.92; 95% confidence interval (CI): 0.86-0.98) compared to low blood levels of n-6 PUFAs. In the subgroup analyses by cancer site, type of n-6 PUFAs, and sex, the inverse associations were strong for breast cancer (RR = 0.87; 95% CI: 0.77-0.98), linoleic acid (LA) (RR = 0.91; 95% CI: 0.82-1.00), and women (RR = 0.88; 95% CI: 0.79-0.97). In the dose-response analysis, a 2% and 3% decrease in the risk of cancer was observed with a 5% increase in blood levels of n-6 PUFAs and LA, respectively. Thus, there was no significant association between n-6 PUFA intake and the risk of cancer. The pooled RR of cancer for the highest versus lowest category of n-6 PUFA intake was 1.02 (95% CI: 0.99-1.05). Evidence from prospective studies indicated that intake of n-6 PUFAs was not significantly associated with risk of cancer, but blood levels of n-6 PUFAs were inversely associated with risk of cancer.

A prospective study of erythrocyte polyunsaturated fatty acids and risk of colorectal serrated polyps and conventional adenomas

The influence of polyunsaturated fatty acids (PUFAs) on risk of colorectal cancer precursors remains largely unknown. We examined the associations of erythrocyte PUFAs, including n-3 and n-6 PUFAs, with risk of colorectal conventional adenomas and serrated polyps in 4517 participants from three US prospective cohorts who had provided a blood sample and undergone at least one endoscopic examination. We calculated the multivariable odds ratios (ORs) per 1 SD increment in individual PUFAs and the ratio of n-6/n-3 PUFAs. We considered P < .005 statistically significant to account for multiple testing. During a median of 20 years of follow-up, we documented 493 conventional adenomas and 316 serrated polyps. After adjusting for various CRC risk factors, no associations for PUFAs achieved the stringent statistical significance for either conventional adenomas or serrated polyps (ORs per 1 SD ranged from 0.90 to 1.14). Some associations achieved nominal significance (P < .05), including the association of dihomogammalinolenic acid (DGLA) (20:3, n-6) with lower risk of conventional adenomas (OR = 0.91; 95% confidence interval [CI] = 0.83-1.00), total n-6 PUFAs with higher risk of proximal serrated polyps (OR = 1.32; 95% CI = 1.01-1.74) and eicosadienoic acid (20:2, n-6) and DGLA with lower risk of advanced adenomas (OR = 0.83; 95% CI = 0.71-0.97 and OR = 0.84; 95% CI = 0.72-0.98, respectively). Our findings indicate that erythrocyte PUFAs in a typical American diet are unlikely to have a substantial influence on risk of colorectal cancer precursors. The subgroup associations require further confirmation.

Dietary Intake of N-3 and N-6 Polyunsaturated Fatty Acids and Risk of Cancer: Meta-Analysis of Data from 32 Studies

BACKGROUND

Large epidemiological studies have yielded conflicting results regarding the relationship between polyunsaturated fatty acids (PUFAs) and cancers. Here, we performed a meta-analysis to examine the link between dietary intake of n-3 and n-6 PUFAs and cancer risk.

MATERIALS AND METHODS

We performed a search on PubMed, EMBASE, and the Cochrane Library. Studies that reported adjusted relative risk (RR) estimates with 95% confidence intervals (CI) for the associations of interest were included.

RESULTS

Thirty-two studies involving 1,445,732 participants were included. Colorectal, breast and prostate cancer had been analyzed in our study. Specifically, for colorectal cancer, total n-3 PUFAs, marine n-3 PUFAs, α-linolenic acids (ALA) and n-6 PUFAs were not associated with the risk of it (RR 1.04, 95%CI 0.85-1.28; RR 0.99, 95%CI 0.89-1.09; RR 1.05, 95%CI 0.93-1.19; RR 1.02, 95%CI 0.94-1.11, respectively). For breast cancer, only marine n-3 PUFAs, but not total n-3 PUFAs, ALA, and n-6 PUFAs, was associated with a lower risk of it (RR 0.70, 95%CI 0.55-0.91). For prostate cancer, ALA and n-6 PUFAs also have no association with the risk of it.

CONCLUSIONS

Most subtypes of PUFAs are probably not related to cancers. However, additional high-quality trials are warranted to corroborate the findings of this meta-analysis.

Omega-3 PUFA intake and the risk of digestive system cancers: A meta-analysis of observational studies

BACKGROUND

A growing number of epidemiological studies have suggested a possible association between long-chain omega-3 polyunsaturated fatty acid (PUFA) intake and the risk of cancers, but the results have been inconsistent. We aimed to conduct a meta-analysis to assess the association of omega-3 PUFA consumption with digestive system cancers.

METHODS

Relevant observational studies were identified through a comprehensive search of PubMed, Embase, and the Web of Science through December 2019 and by reviewing the references of the retrieved articles. The relative risks (RRs) of digestive system cancers associated with omega-3 PUFA intake were estimated using a random-effect model and were stratified by region, sex, study design, type of omega-3 PUFAs, smoking status, alcohol consumption, BMI, and physical activity.

RESULTS

Twenty-five studies (8 case-control studies and 17 cohort studies) involving 1,247,271 participants and 23,173 patients with digestive system cancers were included in this analysis. The risk of digestive system cancers decreased by 17% in individuals who consumed omega-3 PUFAs (RR = 0.83, 95% confidence interval (CI), 0.76-0.91). The risk estimates of digestive system cancers varied by cancer sites, study location, study design, type of omega-3 PUFAs, and other confounders (smoking, alcohol consumption, body mass index, and physical activity). Visual inspection of funnel plots and the Begg's and Egger's tests revealed no evidence of publication bias.

CONCLUSION

The findings show that omega-3 PUFAs should be as a healthy dietary component for the prevention of digestive system cancers. Cancer incidence decreases with increasing omega-3 PUFAs intake for most digestive system cancer sites. The relation between omega-3 PUFAs and digestive system cancers RR is similar among different populations.

Dietary nutrient patterns and the risk of colorectal cancer and colorectal adenomas: a case-control study

Although the association between food patterns and the risk of colorectal cancer (CRC) and colorectal adenomas (CRA) has been explored previously, a distinct paucity of studies has evaluated the association of nutrient pattern and the risk of CRC and CRA as precursors of CRC. Thus, the purpose of this case-control study was to investigate nutrient patterns and their relationship with CRC and CRA in Iran. Two hundred forty hospital control, 129 newly diagnosed CRC and 130 newly diagnosed CRA patients were asked about their dietary intakes using validated questionnaires. To define the major nutrient patterns, principal component analysis was applied based on preselected nutrients, and four explainable nutrient patterns were obtained: Factor 1 (mixed), factor 2 (the antioxidant), factor 3 (dairy) and factor 4 (the high fat). Logistic regression was used to determine odds ratios (OR) with 95% confidence interval (CI) of CRC and CRA according to categories of nutrient patterns. After adjusting for confounders, factor 2 was significantly associated with lower risk for the CRC and CRA in the second category compared with the first, respectively (OR = 0.20, 95% CI: 0.12-0.34, OR = 0.34, 95% CI: 0.21-0.56). Participants in the highest category of factor 4 showed an increase in the risk of CRC and CRA, respectively, than those in the low category, in both crude and multivariate analysis (OR = 1.77, 95% CI: 1.57-2.95, OR = 1.85, 95% CI: 1.13-3.02). Among derived nutrient patterns, 'the antioxidant pattern' was inversely associated with CRC/CRA, whilst 'high fat pattern' showed a direct association with these diseases.

Intake or Blood Levels of n-3 Polyunsaturated Fatty Acids and Risk of Colorectal Cancer: A Systematic Review and Meta-analysis of Prospective Studies

BACKGROUND

Previous results of the association between n-3 polyunsaturated fatty acids (PUFA) and colorectal cancer were inconsistent. We conducted a systematic review and meta-analysis of prospective studies.

METHODS

The PubMed and Embase databases were searched through July 10, 2019, followed by a manual search. A random-effects model was used.

RESULTS

Twenty prospective studies, including 18,102 cases and 1,360,046 participants, were included. The pooled RR of colorectal cancer for the highest versus lowest category of n-3 PUFA intake was 0.97 [95% confidence interval (CI), 0.90-1.04]. Regarding the type of n-3 PUFA, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intakes were inversely associated with 11% (RR = 0.89; 95% CI, 0.80-0.99) and 12% (RR = 0.88; 95% CI, 0.81-0.96) lower colorectal cancer risks, respectively, in the comparison of the highest versus lowest category. Increments of 0.1 g/day of EPA (RR = 0.95; 95% CI, 0.92-0.98) and DHA (RR = 0.97; 95% CI, 0.95-0.99) intakes were associated with a lower colorectal cancer risk. Regarding the blood levels of n-3 PUFAs, the pooled RR of colorectal cancer for the highest versus lowest category of blood levels of n-3 PUFAs was 0.79 (95% CI, 0.64-0.98). The risk of colorectal cancer decreased by 4% for every 1% increase in blood n-3 PUFA levels (RR = 0.96; 95% CI, 0.92-1.00).

CONCLUSIONS

High blood n-3 PUFA levels are inversely associated with colorectal cancer risk, and high n-3 PUFA intake is suggestively associated with lower colorectal cancer risk.

IMPACT

Our findings suggest that high blood n-3 PUFA levels may be associated with reduced colorectal cancer risk, but further studies are needed.

Dietary Fat Intake and Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis of Prospective Studies

Dietary fat intake is associated with the risk of colorectal cancer (CRC); however, the results of epidemiological studies on this are controversial. Therefore, this study aimed to summarize the available scientific evidence regarding the association between dietary fat and the risk of CRC. We conducted a systematic search of PubMed, Web of Science, and the Cochrane library for articles related to dietary fat and the risk of CRC. The summary relative risks with 95% confidence intervals (CI) were calculated via a random effect model. Begg’s test was used to detect publication bias. A total of 18 articles were identified. The pooled relative risk with 95% CI for the risk of CRC were 1.00 (95% CI: 0.90–1.12), 0.97 (95% CI: 0.86–1.10), 1.08 (95% CI: 0.92–1.26), and 0.99 (95% CI: 0.93–1.04) for total fat, saturated fatty acid, monounsaturated fatty acid, and polyunsaturated fatty acid, respectively. No significant associations were found in subgroup analyses. Begg’s test for all exposures revealed no publication bias (total fat, p = 0.3; saturated fatty acid, p = 0.1; monounsaturated fatty acid, p = 0.08; polyunsaturated fatty acid, p = 0.2). The studies included in this review and meta-analysis revealed that dietary fats and fatty acids had no effects on the risk of CRC.

A prospective study of dietary polyunsaturated fatty acids intake and lung cancer risk

Animal studies have shown that polyunsaturated fatty acids (PUFAs) have antineoplastic and anti-inflammatory properties. Results from epidemiologic studies on specific types of PUFAs for lung cancer risk, however, are inconclusive. We prospectively evaluated the association of specific types of dietary PUFA intakes and lung cancer risk in two population-based cohort studies, the Shanghai Women's Health Study (SWHS) and Shanghai Men's Health Study (SMHS) with a total of 121,970 study participants (i.e., 65,076 women and 56,894 men). Dietary fatty acid intakes were derived from data collected at the baseline using validated food frequency questionnaires (FFQs). Cox proportional hazards model was performed to assess the association between PUFAs and lung cancer risk. Total, saturated and monounsaturated fatty acid intakes were not significantly associated with lung cancer risk. Total PUFAs intake was inversely associated with lung cancer risk [HRs and respective 95% CIs for quintiles 2-5 vs quintile 1: 0.84 (0.71-0.98), 0.97 (0.83-1.13), 0.86 (0.74-1.01) and 0.85 (0.73-1.00), ptrend  = 0.11]. However, DHA intake was positively associated with lung cancer risk [HRs and 95% CIs: 1.01 (0.86-1.19), 1.20 (1.03-1.41), 1.21 (1.03-1.42) and 1.24 (1.05-1.47), ptrend  = 0.001]. The ratio of n-6 PUFAs to n-3 PUFAs (i.e., 7:1) was inversely associated with lung cancer risk, particularly among never-smokers and adenocarcinoma patients. Total PUFAs and the ratio between n-6 PUFAs and n-3 PUFAs were inversely associated with lung cancer risk. This study highlights an important public health impact of PUFA intakes toward intervention/prevention programs of lung cancer.

Evaluation of the Impact of Cancer Treatment on the Adoption and Consolidation of Pro-Health Attitudes in the Field of Cancer in Treated Patients with Colon Cancer

Colorectal cancer is the second most common cause of cancer deaths worldwide. Although progress in the development of new drugs over the last two decades has expanded treatment options for this disease, many significant problems relating to their optimization remain to be solved. Data on the cancer knowledge and the healthy behavior and lifestyle in patients with colorectal cancer in Poland is missing. We analyzed the course and results of treatment of first-line chemotherapy in 165 patients diagnosed with colorectal cancer treated between May 2010 and December 2013. The respondent's knowledge in the field of cancer and their lifestyle before and after the treatment were rated. The results were compared with a control group. Mean age was 60.89 ± 8.69 years, median 59 years. The general knowledge about cancer and the level of healthy lifestyle before treatment were low. After treatment, both the knowledge about cancer and the level of healthy lifestyle increased compared to the control group. There was a clear relationship between the level of knowledge about cancer and the willingness to adopt attitudes and healthy behavior by patients. In our analysis, the overall quality of life in patients treated with first-line palliative chemotherapy of colorectal cancer did not change during treatment. Our results indicate the need to implement an educational program on cancer prevention in treated patients, and the analysis of quality of life and other factors than treatment effect remains controversial.

The impact of the Standard American Diet in rats: Effects on behavior, physiology and recovery from inflammatory injury

BACKGROUND AND AIMS

Obesity is a significant health concern in the Western world and the presence of comorbid conditions suggests an interaction. The overlapping distributions of chronic pain populations and obesity suggests that an interaction may exist. Poor quality diet (high carbohydrates, saturated fats, omega-6 polyunsaturated fatty acids) can lead to increased adiposity which can activate immune cells independent of the activating effect of the diet components themselves. This dual action can contribute to chronic inflammation that may alter susceptibility to chronic pain and prolong recovery from injury. However, traditional examinations of diet focus on high-fat diets that often contain a single source of fat, that is not reflective of an American diet. Thus, we examined the impact of a novel human-relevant (high-carbohydrate) American diet on measures of pain and inflammation in rats, as well as the effect on recovery and immune cell activation.

METHODS

We developed a novel, human-relevant Standard American Diet (SAD) to better model the kilocalorie levels and nutrient sources in an American population. Male and female rats were fed the SAD over the course of 20 weeks prior to persistent inflammatory pain induction with Complete Freund's Adjuvant (CFA). Mechanical and thermal sensitivity were measured weekly. Spontaneous pain, open field locomotion and blood glucose levels were measured during diet consumption. Body composition was assessed at 20 weeks. Following full recovery from CFA-induced hypersensitivity, blood was analyzed for inflammatory mediators and spinal cords were immunohistochemically processed for microglial markers.

RESULTS

Chronic consumption of the SAD increased fat mass, decreased lean mass and reduce bone mineral density. SAD-fed rats had increased leptin levels and pro-inflammatory cytokines in peripheral blood serum. Following CFA administration, mechanical sensitivity was assessed and recovery was delayed significantly in SAD-fed animals. Sex differences in the impact of the SAD were also observed. The SAD increased body weight and common T-cell related inflammatory mediators in female, but not male, animals. In males, the SAD had a greater effect on bone mineral density and body composition. Long-term consumption of the SAD resulted in elevated microglial staining in the dorsal horn of the spinal cord, but no sex differences were observed.

CONCLUSIONS

We demonstrate the negative effects of an American diet on physiology, behavior and recovery from injury. SAD consumption elevated pro-inflammatory mediators and increased microglial activation in the spinal cord. While there were sex differences in weight gain and inflammation, both sexes showed prolonged recovery from injury.

IMPLICATIONS

These data suggest that poor quality diet may increase susceptibility to chronic pain due to persistent peripheral and central immune system activation. Furthermore, consumption of a diet that is high in carbohydrates and omega-6 polyunsaturated fatty acid is likely to lead to protracted recovery following trauma or surgical procedures. These data suggest that recovery of a number of patients eating a poor quality diet may be expedited with a change in diet to one that is healthier.

PUFA levels in erythrocyte membrane phospholipids are differentially associated with colorectal adenoma risk

Dietary intake of PUFA has been associated with colorectal neoplasm risk; however, results from observational studies have been inconsistent. Most prior studies have utilised self-reported dietary measures to assess fatty acid exposure which might be more susceptible to measurement error and biases compared with biomarkers. The purpose of this study was to determine whether erythrocyte phospholipid membrane PUFA percentages are associated with colorectal adenoma risk. We included data from 904 adenoma cases and 835 polyp-free controls who participated in the Tennessee Colorectal Polyp Study, a large colonoscopy-based case-control study. Erythrocyte membrane PUFA percentages were measured using GC. Conditional logistic regression was used to calculate adjusted OR for risk of colorectal adenomas with erythrocyte membrane PUFA. Higher erythrocyte membrane percentages of arachidonic acid was associated with an increased risk of colorectal adenomas (adjusted OR 1·66; 95 % CI 1·05, 2·62, P trend=0·02) comparing the highest tertile to the lowest tertile. The effect size for arachidonic acid was more pronounced when restricting the analysis to advanced adenomas only. Higher erythrocyte membrane EPA percentages were associated with a trend towards a reduced risk of advanced colorectal adenomas (P trend=0·05). Erythrocyte membrane arachidonic acid percentages are associated with an increased risk of colorectal adenomas.

Marine ω-3 Polyunsaturated Fatty Acid Intake and Risk of Colorectal Cancer Characterized by Tumor-Infiltrating T Cells

IMPORTANCE

Marine ω-3 polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid, docosahexaenoic acid, and docosapentaenoic acid, possess potent immunomodulatory activity and may protect against cancer development. However, evidence relating marine ω-3 PUFAs to colorectal cancer (CRC) risk remains inconclusive.

OBJECTIVE

To test the hypothesis that marine ω-3 PUFA intake may be associated with lower risk of CRC subsets characterized by immune infiltrate.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study was conducted among participants in the Nurses' Health Study (1984-2010) and Health Professionals Follow-up Study (1986-2010).

EXPOSURES

Intake of marine ω-3 PUFAs.

MAIN OUTCOMES AND MEASURES

Incidence of CRC characterized by CD3+, CD8+, CD45RO (PTPRC)+, or FOXP3+ T-cell densities in tumor tissue, measured by immunohistochemical and computer-assisted image analysis.

RESULTS

Among 173 229 predominantly white participants, 125 172 with 2 895 704 person-years of follow-up provided data about marine ω-3 PUFA intake every 4 years through a validated food frequency questionnaire and followed up for incident CRC evaluation. Of 2504 CRC cases, we documented 614 (252 men, 362 women) from which we could assess T-cell infiltration in the tumor microenvironment. The inverse association of marine ω-3 PUFAs intake with CRC risk differed according to FOXP3+ T-cell infiltration: compared with intake of less than 0.15 g/d of marine ω-3 PUFAs, intake of at least 0.35 g/d was associated with a multivariable hazard ratio (HR) of 0.57 (95% CI, 0.40-0.81; P < .001 for trend) for FOXP3+ T-cell-high tumors. In contrast, the HR for FOXP3+ T-cell-low tumors was 1.14 (95% CI, 0.8-1.60) (P = .77 for trend; P = .01 for heterogeneity). No statistically significant differential association was found for high-density tumors (compared with low-density tumors) according to CD3+, CD8+, or CD45RO+ cell density (P ≥ .34 for heterogeneity for all comparisons). In functional assays, the suppressive activity of regulatory T cells was approximately 2-fold lower (T-effector-cell proliferation, ≥64% vs 38%) when preincubated with docosahexaenoic acid at 50μM, 100μM, and 200μM concentrations than without docosahexaenoic acid (P < .001 for all comparisons).

CONCLUSIONS AND RELEVANCE

High marine ω-3 PUFA intake was associated with lower risk of CRC with high-level, but not low-level, FOXP3+ T-cell density, suggesting a potential role of ω-3 PUFAs in cancer immunoprevention through modulation of regulatory T cells.

Sex-specific effects of docosahexaenoic acid (DHA) on the microbiome and behavior of socially-isolated mice

Dietary supplementation with the long-chain omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) has been shown to have a beneficial effect on reducing the symptoms associated with several neuropsychiatric conditions including anxiety and depression. However, the mechanisms underlying this effect remain largely unknown. Increasing evidence suggests that the vast repertoire of commensal bacteria within the gut plays a critical role in regulating various biological processes in the brain and may contribute to neuropsychiatric disease risk. The present study determined the contribution of DHA on anxiety and depressive-like behaviors through modulation of the gut microbiota in a paradigm of social isolation. Adult male and female mice were subjected to social isolation for 28days and then placed either on a control diet or a diet supplemented with 0.1% or 1.0% DHA. Fecal pellets were collected both 24h and 7days following the introduction of the new diets. Behavioral testing revealed that male mice fed a DHA diet, regardless of dose, exhibited reduced anxiety and depressive-like behaviors compared to control fed mice while no differences were observed in female mice. As the microbiota-brain-axis has been recently implicated in behavior, composition of microbial communities were analyzed to examine if these sex-specific effects of DHA may be associated with changes in the gut microbiota (GM). Clear sex differences were observed with males and females showing distinct microbial compositions prior to DHA supplementation. The introduction of DHA into the diet also induced sex-specific interactions on the GM with the fatty acid producing a significant effect on the microbial profiles in males but not in females. Interestingly, levels of Allobaculum and Ruminococcus were found to significantly correlate with the behavioral changes observed in the male mice. Predictive metagenome analysis using PICRUSt was performed on the fecal samples collected from males and identified enrichment in functional KEGG pathway terms relevant to processes such as the biosynthesis of unsaturated fatty acids and antioxidant metabolism. These results indicate that DHA alters commensal community composition and produces beneficial effects on anxiety and depressive-like behaviors in a sex-specific manner. The present study provides insight into the mechanistic role that gut microbes may play in the regulation of anxiety and depressive-like behaviors and how dietary intervention can modulate these effects.

The Interaction between Dietary Fiber and Fat and Risk of Colorectal Cancer in the Women's Health Initiative

Combined intakes of specific dietary fiber and fat subtypes protect against colon cancer in animal models. We evaluated associations between self-reported individual and combinations of fiber (insoluble, soluble, and pectins, specifically) and fat (omega-6, omega-3, and docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), specifically) and colorectal cancer (CRC) risk in the Women's Health Initiative prospective cohort (n = 134,017). During a mean 11.7 years (1993-2010), 1952 incident CRC cases were identified. Cox regression models computed multivariate adjusted hazard ratios to estimate the association between dietary factors and CRC risk. Assessing fiber and fat individually, there was a modest trend for lower CRC risk with increasing intakes of total and insoluble fiber (p-trend 0.09 and 0.08). An interaction (p = 0.01) was observed between soluble fiber and DHA + EPA, with protective effects of DHA + EPA with lower intakes of soluble fiber and an attenuation at higher intakes, however this association was no longer significant after correction for multiple testing. These results suggest a modest protective effect of higher fiber intake on CRC risk, but not in combination with dietary fat subtypes. Given the robust results in preclinical models and mixed results in observational studies, controlled dietary interventions with standardized intakes are needed to better understand the interaction of specific fat and fiber subtypes on colon biology and ultimately CRC susceptibility in humans.

Role of diets rich in omega-3 and omega-6 in the development of cancer

Over the past decade, some studies have addressed the therapeutic effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) and the opposite effects of omega-6 (ω-6) PUFAs on several diseases, including cardiovascular disorders, diabetes, neurodegenerative diseases, and cancer. Research demonstrates the safety of these naturally occurring ingredients. Of particular interest, several studies have shown that ω-3 PUFAs possess a therapeutic role against certain types of cancer. It is also known that ω-3 PUFAs can improve the efficacy and tolerability of chemotherapy. Previous reports have indicated that suppression of nuclear factor-κB, activation of AMPK/SIRT1, modulation of cyclooxygenase (COX) activity, and up-regulation of novel anti-inflammatory lipid mediators such as protectins, maresins, and resolvins, are the main mechanisms of the antineoplastic effect of ω-3 PUFAs. In contrast, several studies have demonstrated that ω-6 PUFAs induce progression in certain types of cancer. In this review, we discuss epidemiological and experimental studies addressing the relationship between the development of some types of cancer, including colon and colorectal carcinoma, breast cancer, prostate cancer, lung cancer and neuroblastoma, and the ingestion to ω-3 and ω-6 (PUFAs). We also discuss the clinical data, addressing the therapeutic role of omega-3 PUFA against different types of cancer.

Plasma eicosapentaenoic acid is negatively associated with all-cause mortality among men and women in a population-based prospective study

Omega-3 polyunsaturated fatty acids (PUFAs) have anti-inflammatory properties, whereas omega-6 PUFAs appear to have proinflammatory properties. We aimed to assess plasma omega-3 and omega-6 PUFA status in relation to all-cause mortality in an Australian community-based study. We hypothesized that omega-3 PUFA would be inversely associated, and omega-6 PUFA positively associated with all-cause mortality. Plasma phospholipid omega-3 (eicosapentaenoic acid [EPA], docosapentaenoic acid [DPA], docosahexaenoic acid, α-linolenic acid, and total) and omega-6 PUFAs (linoleic acid, arachidonic acid, and total) were measured among 1008 adults (44% men) in 1996. Plasma PUFA composition was quantified using gas chromatography. During 17-year follow-up, 98 men and 81 women died. After adjustment for potential confounding factors, plasma EPA was inversely associated with all-cause mortality overall (adjusted hazard ratio [HR] per 1-SD increase, 0.81; 95% confidence interval [CI], 0.68-0.95), in men (HR, 0.78; 95% CI, 0.62-0.98), and in women (HR, 0.78; 95% CI, 0.65-0.94), separately. Inverse associations with mortality among men were also seen for DPA (HR, 0.76; 95% CI, 0.60-0.97) and α-linolenic acid (HR, 0.73; 95% CI, 0.57-0.94). No omega-6 PUFAs were significantly associated with mortality. Our findings of reduced all-cause mortality in men and women who have high EPA in plasma, and in men with high plasma DPA and α-linolenic acid, partially support our hypothesis that omega-3 PUFAs help reduce mortality but provide no evidence that omega-6 PUFAs may increase mortality.

Technological trends and market perspectives for production of microbial oils rich in omega-3

In recent years, foods that contain omega-3 lipids have emerged as important promoters of human health. These lipids are essential for the functional development of the brain and retina, and reduction of the risk of cardiovascular and Alzheimer's diseases. The global market for omega-3 production, particularly docosahexaenoic acid (DHA), saw a large expansion in the last decade due to the increasing use of this lipid as an important component of infant food formulae and supplements. The production of omega-3 lipids from fish and vegetable oil sources has some drawbacks, such as complex purification procedures, unwanted contamination by marine pollutants, reduction or even extinction of several species of fish, and aspects related to sustainability. A promising alternative system for the production of omega-3 lipids is from microbial metabolism of yeast, fungi, or microalgae. The aim of this review is to discuss the various omega-3 sources in the context of the global demand and market potential for these bioactive compounds. To summarize, it is clear that fish and vegetable oil sources will not be sufficient to meet the future needs of the world population. The biotechnological production of single-cell oil comes as a sustainable alternative capable of supplementing the global demand for omega-3, causing less environmental impact.

Evidence-Based Guideline of the German Nutrition Society: Fat Intake and Prevention of Selected Nutrition-Related Diseases

As nutrition-related chronic diseases have become more and more frequent, the importance of dietary prevention has also increased. Dietary fat plays a major role in human nutrition, and modification of fat and/or fatty acid intake could have a preventive potential. The aim of the guideline of the German Nutrition Society (DGE) was to systematically evaluate the evidence for the prevention of the widespread diseases obesity, type 2 diabetes mellitus, dyslipoproteinaemia, hypertension, metabolic syndrome, coronary heart disease (CHD), stroke, and cancer through the intake of fat or fatty acids. The main results can be summarized as follows: it was concluded with convincing evidence that a reduced intake of total and saturated fat as well as a larger intake of polyunsaturated fatty acids (PUFA) at the expense of saturated fatty acids (SFA) reduces the concentration of total and low-density lipoprotein cholesterol in plasma. Furthermore, there is convincing evidence that a high intake of trans fatty acids increases risk of dyslipoproteinaemia and that a high intake of long-chain polyunsaturated n-3 fatty acids reduces the triglyceride concentration in plasma. A high fat intake increases the risk of obesity with probable evidence when total energy intake is not controlled for (ad libitum diet). When energy intake is controlled for, there is probable evidence for no association between fat intake and risk of obesity. A larger intake of PUFA at the expense of SFA reduces risk of CHD with probable evidence. Furthermore, there is probable evidence that a high intake of long-chain polyunsaturated n-3 fatty acids reduces risk of hypertension and CHD. With probable evidence, a high trans fatty acid intake increases risk of CHD. The practical consequences for current dietary recommendations are described at the end of this article.

A review of recent evidence in human studies of n-3 and n-6 PUFA intake on cardiovascular disease, cancer, and depressive disorders: does the ratio really matter?

Polyunsaturated fatty acids (PUFAs) have been considered of great interest for human health due to their potential anti-inflammatory action that may protect from a number of chronic-degenerative diseases with an inflammatory pathogenesis. This review aimed to report the most updated evidence of both n-3 and n-6 PUFAs effect on cardiovascular disease, cancer, and depression in humans. Attention has been also paid to those studies exploring the effects of the ratio intake. Results from pooled analyses of human studies reported a general positive effect of n-3 PUFAs intake on all outcomes considered. In contrast, the role of n-6 PUFAs on human health needs to be better assessed in order to clearly identify which compound exerts beneficial/harmful effects. Only a limited number of clinical studies considered the n-3:n-6 PUFAs ratio, rather reporting contrasting results. A number of limitations when considering the ratio between these two families of PUFAs have risen.

Prevention of diabetes-promoted colorectal cancer by (n-3) polyunsaturated fatty acids and (n-3) PUFA mimetic

The global obesity / diabetes epidemic has resulted in robust increase in the incidence of colorectal cancer (CRC). Epidemiological, animal and human studies have indicated efficacy of (n-3) PUFA in chemoprevention of sporadic and genetic-driven CRC. However, diabetes-promoted CRC presents a treatment challenge that surpasses that of sporadic CRC. This report analyzes the efficacy of (n-3) PUFA generated by the fat-1 transgene that encodes an (n-6) to (n-3) PUFA desaturase, and of synthetic (n-3) PUFA mimetic (MEDICA analog), to suppress CRC development in carcinogen-induced diabetes-promoted animal model. Carcinogen-induced CRC is shown here to be promoted by the diabetes context, in terms of increased aberrant crypt foci (ACF) load, cell proliferation and epithelial dedifferentiation, being accompanied by increase in the expression of HNF4α, β-catenin, and β-catenin-responsive genes. Incorporating the fat-1 transgene in the diabetes context, or oral MEDICA treatment, resulted in ameliorating the diabetic phenotype and in abrogating CRC, with decrease in ACF load, cell proliferation and the expression of HNF-4α, β-catenin, and β-catenin-responsive genes. The specificity of (n-3) PUFA in abrogating CRC development, as contrasted with enhancing CRC by (n-6) PUFA, was similarly verified in CRC cell lines. These findings may indicate prospective therapeutic potential of (n-3) PUFA or MEDICA in the management of CRC, in particular diabetes-promoted CRC.

Dietary Fiber Intake Modifies the Positive Association between n-3 PUFA Intake and Colorectal Cancer Risk in a Caucasian Population

BACKGROUND

The association between dietary fat intake and the risk of colorectal cancer (CRC) is still unclear.

OBJECTIVES

We analyzed whether intakes of dietary polyunsaturated fatty acids (PUFAs) and saturated fatty acids (SFAs) were associated with CRC risk and whether these associations were modified by dietary fiber (DF) intake.

METHODS

This study was embedded in the Rotterdam Study, a prospective cohort study among subjects aged ≥55 y (n = 4967). At baseline, diet was measured by a food-frequency questionnaire. CRC events were diagnosed on the basis of pathology data and medical records. Multivariable adjusted HRs were calculated using Cox regression models.

RESULTS

During a mean follow-up period of 14.6 y, we identified 222 incident cases of CRC. There was no association between total PUFA, n-6 (ω-6) PUFA, or SFA intake and CRC risk. n-3 PUFA intake was associated with an increased risk of CRC [tertile 3 vs. tertile 1: HR = 1.44 (95% CI: 1.02, 2.04), P-trend = 0.04]. When data were analyzed by food sources, only n-3 PUFAs from nonmarine sources were associated with an increased risk of CRC. A significant interaction between n-3 PUFA and DF intakes was found (P-interaction = 0.02). After stratification by median DF intake, an increased risk of CRC caused by n-3 PUFA intake was observed in participants with a DF intake less than the median [tertile 3 vs. tertile 1: HR = 1.96 (95% CI: 1.20, 3.19), P-trend = 0.01]. No association was observed in subjects with DF intake equal to or higher than the median.

CONCLUSIONS

This study suggests that intake of n-3 PUFAs by adults is associated with an increased risk of CRC, which may be driven mainly by sources other than fish. Moreover, a complex interaction with DF intake may be present.

Nutrients, foods, and colorectal cancer prevention

Diet has an important role in the development of colorectal cancer. In the past few decades, findings from extensive epidemiologic and experimental investigations have linked consumption of several foods and nutrients to the risk of colorectal neoplasia. Calcium, fiber, milk, and whole grains have been associated with a lower risk of colorectal cancer, and red meat and processed meat have been associated with an increased risk. There is substantial evidence for the potential chemopreventive effects of vitamin D, folate, fruits, and vegetables. Nutrients and foods also may interact, as a dietary pattern, to influence colorectal cancer risk. Diet likely influences colorectal carcinogenesis through several interacting mechanisms. These include the direct effects on immune responsiveness and inflammation, and the indirect effects of overnutrition and obesity-risk factors for colorectal cancer. Emerging evidence also implicates the gut microbiota as an important effector in the relationship between diet and cancer. Dietary modification therefore has the promise of reducing colorectal cancer incidence.

Diet, the gut microbiome, and epigenetics

Increasingly, the gut microbiome is implicated in the etiology of cancer, not only as an infectious agent but also by altering exposure to dietary compounds that influence disease risk. Whereas the composition and metabolism of the gut microbiome is influenced by diet, the gut microbiome can also modify dietary exposures in ways that are beneficial or detrimental to the human host. The colonic bacteria metabolize macronutrients, either as specialists or in consortia of bacteria, in a variety of diverse metabolic pathways. Microbial metabolites of diet can also be epigenetic activators of gene expression that may influence cancer risk in humans. Epigenetics involves heritable changes in gene expression via post-translational and post-transcriptional modifications. Microbial metabolites can influence epigenetics by altering the pool of compounds used for modification or by directly inhibiting enzymes involved in epigenetic pathways. Colonic epithelium is immediately exposed to these metabolites, although some metabolites are also found in systemic circulation. In this review, we discuss the role of the gut microbiome in dietary metabolism and how microbial metabolites may influence gene expression linked to colon cancer risk.

Marine ω-3 polyunsaturated fatty acids and risk of colorectal cancer according to microsatellite instability

BACKGROUND

Chronic inflammation is involved in the development of colorectal cancer (CRC) and microsatellite instability (MSI), a distinct phenotype of CRC. Experimental evidence indicates an anti-inflammatory and antineoplastic effect of marine ω-3 polyunsaturated fatty acids (PUFAs). However, epidemiologic data remain inconclusive.

METHODS

We investigated whether the association between marine ω-3 PUFAs and CRC varies by MSI-defined subtypes of tumors in the Nurses' Health Study and Health Professionals Follow-up Study. We documented and classified 1125 CRC cases into either MSI-high tumors, in which 30% or more of the 10 microsatellite markers demonstrated instability, or microsatellite-stable (MSS) tumors. Cox proportional hazards model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of MSS tumors and MSI-high tumors in relation to marine ω-3 PUFA intake. All statistical tests were two-sided.

RESULTS

Marine ω-3 PUFA intake was not associated with overall incidence of CRC. However, a statistically significant difference was detected by MSI status (P heterogeneity = .02): High marine ω-3 PUFA intake was associated with a lower risk of MSI-high tumors (comparing ≥0.30g/d with <0.10g/d: multivariable HR = 0.54, 95% CI = 0.35 to 0.83, P linearity = .03) but not MSS tumors (HR = 0.97, 95% CI = 0.78 to 1.20, P linearity = .28). This differential association appeared to be independent of CpG island methylator phenotype and BRAF mutation status.

CONCLUSIONS

High marine ω-3 PUFA intake is associated with lower risk of MSI-high CRC but not MSS tumors, suggesting a potential role of ω-3 PUFAs in protection against CRC through DNA mismatch repair. Further research is needed to confirm our findings and elucidate potential underlying mechanisms.

Dietary and biomarker estimates of fatty acids and risk of colorectal cancer

The associations between intake of or circulating fatty acids and risk of colorectal cancer (CRC) are unclear. We examined prospectively the associations between dietary or biomarker fatty acids and CRC. For 41,514 men and women, aged 40-69 years, baseline (1990-94) dietary intakes of fatty acids were estimated using a food frequency questionnaire and plasma phospholipid (PPL) fatty acids were measured for 4,205 participants including 395 CRC cases, according to a case-cohort design. Hazard ratios were computed using Cox regression adjusting for education, alcohol intake, smoking status, physical activity and total energy intake; and stratified for gender, ethnicity and family history of cancer, with age as the time scale. We assessed the heterogeneity of associations with colon and rectal cancers. PPL saturated fatty acids (SFAs) were positively associated with CRC risk, while total n-3 polyunsaturated fatty acids (PUFA) and long chain marine n-3 PUFAs showed inverse associations, significant only for 22:5 n-3. No significant associations were observed for dietary fatty acid intakes but positive associations with CRC of borderline significance were seen for both dietary and PPL linoleic acid. Positive associations with dietary palmitic acid (16:0), MUFAs and n-6 PUFAs were seen for rectal but not colon cancers. PPL 22:6 n-3 was inversely associated with rectal cancer. Limiting intakes of SFAs and MUFAs could be assisted by following existing guidelines to limit red and processed meats which are important sources in the Australian diet. Our observations regarding linoleic acid should be examined further.

Fatty acid composition of adipose tissue and colorectal cancer: a case-control study

BACKGROUND

Unlike experimental results, epidemiologic studies that used dietary questionnaires were not convincing as regards the relations between dietary fatty acids (FAs) and risk of colorectal cancer (CRC). The FA composition of adipose tissue, which is considered to be an indicator of dietary intake over 2-3 y because of the slow turnover rate, appears promising but has so far been rarely used to explore the relation between CRC and exogenous or endogenously produced FAs.

OBJECTIVE

In this case-control study, we aimed to investigate associations between risk of CRC and the FA composition of subcutaneous adipose tissue and product-to-precursor ratios as indexes of enzymatic activities.

DESIGN

From 2008 to 2011, we recruited 203 cases with newly diagnosed CRC and elective surgery with a curative intent and 223 control subjects with planned abdominal surgery for benign disease and no history of CRC or polyp resection. During surgery, abdominal subcutaneous adipose tissue samples were optimally collected, stored, and analyzed by using high-performance gas chromatography. Multivariate logistic regression was used to estimate ORs for CRC in relation to individual FAs divided into tertiles according to the FA distribution in controls.

RESULTS

After adjustment, significant positive associations with CRC risk were observed in highest compared with lowest tertiles of 16:1n-9 (OR: 1.75; 95% CI: 1.00, 3.06; P-trend = 0.045), 20:3n-6 (OR: 1.79; 95% CI: 1.01, 3.17; P-trend = 0.038), 22:5n-3 (OR: 1.82; 95% CI: 1.06, 3.12; P-trend = 0.023), and the ratio of 18:2n-6 to 18:3n-3 (OR: 2.34; 95% CI: 1.37, 3.98; P-trend = 0.001). Significant inverse associations were observed for 18:3n-3 (OR: 0.48; 95% CI: 0.29, 0.81; P-trend = 0.007). Several product-to-precursor ratios showed significant differences between cases and controls in particular ratios that reflected elongase 2/5 activity.

CONCLUSIONS

CRC patients presented higher concentrations of some FAs but lower concentrations of α-linolenic acid in their subcutaneous adipose tissue than did controls. These results may reflect both dietary patterns and altered FA metabolism but require mechanistic explorations.

N-3 polyunsaturated fatty acids intake and risk of colorectal cancer: meta-analysis of prospective studies

BACKGROUND

Growing body of laboratory evidence supports the beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) on colorectal cancer (CRC) prevention. Epidemiologic studies investigating the relationship between n-3 PUFAs intake and risk of CRC, however, have been inconsistent. We aimed to clarify the relation by conducting a meta-analysis of prospective studies.

METHODS

Eligible studies were identified by searching PubMed database and by carefully reviewing bibliographies of retrieved publications. Summary relative risks (RRs) with their 95 % confidence intervals (CIs) were computed with a random-effects model. Subgroup, meta-regression, and dose-response analyses were performed to explore potential sources of heterogeneity.

RESULTS

A total of 14 prospective studies involving 8,775 cancer cases were included in the final analysis. Overall, total n-3 or marine PUFAs intake was not associated with risk of CRC (RR 0.99 and 1.00). However, there was a trend toward reduced risk of proximal colon cancer (total n-3 PUFAs: RR 0.83, 95 % CI 0.66-1.05; marine PUFAs: RR 0.81, 95 % CI 0.59-1.10) and a significant increased risk of distal colon cancer (total n-3 PUFAs: RR 1.26, 95 % CI 1.06-1.50; marine PUFAs: RR 1.38, 95 % CI 1.11-1.71). Furthermore, marine PUFAs intake accessed longer before diagnosis was associated 21 % reduced risk of CRC (RR 0.79, 95 % CI 0.63-1.00).

CONCLUSION

Overall, this meta-analysis finds no relation between n-3 PUFAs intake and risk of CRC. The observed subsite heterogeneity within colon cancer and the possible effect modification by latency time merit further studies.

Dissociable effects of dorsal and ventral hippocampal DHA content on spatial learning and anxiety-like behavior

Chronic deficiency of dietary docosahexaenoic acid (DHA) during critical developmental windows results in severe deficits in spatial learning, anxiety and hippocampal neuroplasticity that parallel a variety of neuropsychiatric disorders. However, little is known regarding the influence of long-term, multigenerational exposure to dietary DHA enrichment on these same traits. To characterize the potential benefits of multigenerational DHA enrichment, mice were fed a purified 10:1 omega-6/omega-3 diet supplemented with either 0.1% preformed DHA/kg feed weight or 1.0% preformed DHA/kg feed weight through three generations. General locomotor activity, spatial learning, and anxiety-like behavior were assessed in adult male offspring of the third generation. Following behavioral assessments, ventral and dorsal hippocampus was collected for DHA and arachidonic acid (AA) analysis. Animals consuming the 0.1% and 1.0% DHA diet did not differ from control animals for locomotor activity or on performance during acquisition learning, but made fewer errors and showed more stable across-day performance during reversal learning on the spatial task and showed less anxiety-like behavior. Consumption of the DHA-enriched diets increased DHA content in the ventral and dorsal hippocampus in a region-specific manner. DHA content in the dorsal hippocampus predicted performance on the reversal training task. DHA content in the ventral hippocampus was correlated with anxiety-like behavior, but AA content in the dorsal hippocampus was a stronger predictor of this behavior. These results suggest that long-term, multigenerational DHA administration improves performance on some aspects of complex spatial learning, decreases anxiety-like behavior, and that modulation of DHA content in sub-regions of the hippocampus predicts which behaviors are likely to be affected.

Effect of the amount and type of dietary fat on cardiometabolic risk factors and risk of developing type 2 diabetes, cardiovascular diseases, and cancer: a systematic review

The effects of both the amount and quality of dietary fat have been studied intensively during the past decades. Previously, low-fat diets were recommended without much attention to the quality of fat, whereas there is general emphasis on the quality of fat in current guidelines. The objective of this systematic review (SR) was to assess the evidence of an effect of the amount and type of dietary fat on body weight (BW), risk factors, and risk of non-communicable diseases, that is, type 2 diabetes (T2DM), cardiovascular diseases (CVD), and cancer in healthy subjects or subjects at risk for these diseases. This work was performed in the process of updating the fourth edition of the Nordic Nutrition Recommendations from 2004. The literature search was performed in October 2010 covering articles published since January 2000. A complementary search was done in February 2012 covering literature until December 2011. Two authors independently selected articles for inclusion from a total of about 16,000 abstracts according to predefined criteria. Randomized controlled trials (RCT) and prospective cohort studies (PCS) were included as well as nested case-control studies. A few retrospective case-control studies were also included when limited or no data were available from other study types. Altogether 607 articles were quality graded and the observed effects in these papers were summarized. Convincing evidence was found that partial replacement of saturated fat (SFA) with polyunsaturated fat (PUFA) or monounsaturated fat (MUFA) lowers fasting serum/plasma total and LDL cholesterol concentrations. The evidence was probable for a decreasing effect of fish oil on concentration of serum/plasma total triglycerides as compared with MUFA. Beneficial effect of MUFA both on insulin sensitivity and fasting plasma/serum insulin concentration was considered as probable in comparisons of MUFA and carbohydrates versus SFA, whereas no effect was found on fasting glucose concentration in these comparisons. There was probable evidence for a moderate direct association between total fat intake and BW. Furthermore, there was convincing evidence that partial replacement of SFA with PUFA decreases the risk of CVD, especially in men. This finding was supported by an association with biomarkers of PUFA intake; the evidence of a beneficial effect of dietary total PUFA, n-6 PUFA, and linoleic acid (LA) on CVD mortality was limited suggestive. Evidence for a direct association between total fat intake and risk of T2DM was inconclusive, whereas there was limited-suggestive evidence from biomarker studies that LA is inversely associated with the risk of T2DM. However, there was limited-suggestive evidence in biomarker studies that odd-chain SFA found in milk fat and fish may be inversely related to T2DM, but these associations have not been supported by controlled studies. The evidence for an association between dietary n-3 PUFA and T2DM was inconclusive. Evidence for effects of fat on major types of cancer was inconclusive regarding both the amount and quality of dietary fat, except for prostate cancer where there was limited-suggestive evidence for an inverse association with intake of ALA and for ovarian cancer for which there was limited-suggestive evidence for a positive association with intake of SFA. This SR reviewed a large number of studies focusing on several different health outcomes. The time period covered by the search may not have allowed obtaining the full picture of the evidence in all areas covered by this SR. However, several SRs and meta-analyses that covered studies published before year 2000 were evaluated, which adds confidence to the results. Many of the investigated questions remain unresolved, mainly because of few studies on certain outcomes, conflicting results from studies, and lack of high quality-controlled studies. There is thus an evident need of highly controlled RCT and PCS with sufficient number of subjects and long enough duration, specifically regarding the effects of the amount and quality of dietary fat on insulin sensitivity, T2DM, low-grade inflammation, and blood pressure. New metabolic and other potential risk markers and utilization of new methodology in the area of lipid metabolism may provide new insight.

Dietary intake of fish, ω-3 and ω-6 fatty acids and risk of colorectal cancer: A prospective study in U.S. men and women

The association between fish, ω-3 and ω-6 polyunsaturated fatty acid (PUFA) intake and risk of colorectal cancer (CRC) remains inconclusive. Recent prospective studies suggest that the relationship may vary by gender, subsite and duration of follow-up. We followed 123,529 US adults (76,386 women and 47,143 men) without a history of cancer at baseline for 24 to 26 years. Fish and PUFA intake was assessed at baseline and updated every 4 years by using a validated food-frequency questionnaire. We found no overall association between fish, ω-3 and ω-6 PUFA intake and CRC risk with hazard ratio (HR) of 1.03 [95% confidence interval (CI): 0.89-1.20] comparing marine ω-3 intake of ≥ 0.30 g/d versus <0.15 g/d among women and 1.05 (95% CI: 0.85-1.30) comparing intake of ≥ 0.41 g/d versus <0.16 g/d among men. However, fish and marine ω-3 PUFA intake appeared to be positively associated with risk of distal colon cancer in both men and women and inversely with risk of rectal cancer in men. In an analysis based on a limited number of cases, marine ω-3 PUFA intake assessed 12-16 years before diagnosis tended to be inversely associated with CRC risk in men (HR: 0.76; 95% CI: 0.52-1.10). In conclusion, although no overall association between fish, ω-3 or ω-6 PUFA intake was observed with CRC risk, marine ω-3 PUFA may be differentially associated with risk of distal colon and rectal cancers and a long latency may be needed for its protection against CRC in men.

Obesity-related inflammation: implications for older adults

The combination of age-related increases in obesity and inflammation can lead to chronic disease, decreased strength, and physical disability. Lifestyle interventions that include moderate caloric restriction along with aerobic and resistance exercise have shown improvements in metabolic outcomes, strength, and physical function in obese older adults. Although few weight loss studies have addressed diet quality, evidence summarized in this review suggests that encouraging intake of antioxidant-rich fruits and vegetables, high-quality protein, low-glycemic index carbohydrates, and omega-3 fatty acids may further ameliorate obesity-related inflammation. Future controlled trials are indicated to examine the effects of incorporating these foods into multimodal weight loss interventions.

Diet and supplements and their impact on colorectal cancer

BACKGROUND

Colorectal cancer is the third commonest cancer and the third leading cause of cancer death among men and women. It has been proposed that dietary factors are responsible for 70-90% of colorectal cancer and diet optimization may prevent most cases.

AIM

To evaluate the role of dietary components and supplements in colorectal cancer.

METHODS

Bibliographical searches were performed in Pubmed for the terms "diet and colorectal cancer", "diet and colon cancer", "diet and rectal cancer", "nutrition and colorectal cancer", "probiotics and colorectal cancer", "prebiotics and colorectal cancer", "alcohol and cancer" and "colorectal cancer epidemiology".

RESULTS

Consumption of processed or red meat, especially when cooked at high temperatures may be associated with increased risk of colorectal cancer. The evidence for dietary fibre is unclear but foods that contain high amounts of fibre are usually rich in polyphenols which have been shown to alter molecular processes that can encourage colorectal carcinogenesis. Meta-analyses provide evidence on the benefits of circulating, diet-derived and supplemented, vitamin D and Calcium. We also found that diets rich in Folate may prevent colorectal carcinoma. The evidence on dietary micronutrients such as Zinc and Selenium in association with colorectal cancer is not conclusive. It has been suggested that there may be a direct association between alcohol intake and colorectal cancer. In vitro and in vivo studies have highlighted a possible protective role of prebiotics and probiotics.

CONCLUSIONS

The lack of randomized trials and the presence of confounding factors including smoking, physical activity, obesity and diabetes may often yield inconclusive results. Carefully designed randomized trials are recommended.