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

Dietary Factors and the Risk of Colorectal Cancer: A Mendelian Randomization Study

OBJECTIVE

To examine the causal association between 15 dietary factors and the incidence of colorectal cancer through the application of Mendelian randomization methodology.

METHODS

The data associated with 15 dietary factors were derived from the IEU OPEN GWAS database, and the colorectal cancer data were sourced from the FinnGen database. The Inverse Variance Weighting method was the principal research method. Sensitivity analyses were implemented to affirm the robustness of the findings. Additionally, we conducted multivariable Mendelian randomization analyses to adjust for the intake of ω-3 and ω-6 polyunsaturated fatty acids.

RESULTS

In our research, we observed suggestive causal relationships between genetically predicted water intake and the reduced risk of colorectal cancer (OR = 0.54; 95% CI= 0.31 ∼ 0.93; p = 0.028); genetically predicted ω-3 PUFA intake (OR = 1.17; 95% CI= 1.05 ∼ 1.30; p = 0.005) were suggestively associated with the increased risk of colorectal cancer. In the multivariable Mendelian randomization analysis, the effect of ω-3 PUFA intake remains significant after adjusting for the influence of ω-6 PUFA intake. Horizontal pleiotropy was not present in this study.

CONCLUSIONS

There exists a suggestive causal association between increased water intake and decreased risk of colorectal cancer, while ω-3 PUFA intake are suggestive linked to the increased risk of colorectal cancer.

Diabetes Risk Reduction Diet and Colorectal Cancer Risk

BACKGROUND

Diabetes has been associated with colorectal cancer. We evaluated whether adherence to a diabetes risk reduction diet (DRRD) can favorably influence the risk of colorectal cancer.

METHODS

Data came from a multicentric Italian case-control study including 1,953 histologically confirmed colorectal cancer cases and 4,154 hospital controls admitted for acute nonneoplastic diseases. Diet was assessed through a validated and reproducible food frequency questionnaire. The DRRD score was computed assigning higher values for higher consumption of cereal fiber, fruit, coffee, nuts and a higher polyunsaturated/saturated fats ratio and for lower glycemic index and lower consumption of red/processed meat and sweetened beverages and fruit juices. The ORs and the corresponding 95% confidence intervals (CI) of colorectal cancer according to the DRRD score were obtained using logistic regression models adjusting for total energy intake and other major confounders.

RESULTS

The DRRD was inversely related to colorectal cancer risk. The ORs of colorectal cancer were 0.77 (95% CI, 0.67-0.89) for the third versus first score tertile (Ptrend < 0.001) and 0.92 (95% CI, 0.87-0.96) for a 3-point increment in the score. Inverse associations were observed for colon and rectal cancers and were consistent in strata of sex, age, and other major covariates.

CONCLUSIONS

A higher adherence to a DRRD was inversely associated with colorectal cancer risk.

IMPACT

Given the high incidence and mortality rates of colorectal cancer, adherence to a DRRD can have relevant prevention and public health implications.

Associations of plasma omega-6 and omega-3 fatty acids with overall and 19 site-specific cancers: a population-based cohort study in UK Biobank

Background

Previous epidemiological studies of the associations between polyunsaturated fatty acids (PUFAs) and cancer incidence have been inconsistent. We investigated the associations of plasma omega-3 and omega-6 PUFAs with the incidence of overall and 19 site-specific cancers in a large prospective cohort.

Methods

253,138 eligible UK Biobank participants were included in our study. With a mean follow-up of 12.9 years, 29,838 participants were diagnosed with cancer. The plasma levels of omega-3 and omega-6 PUFAs were expressed as percentages of total fatty acids (omega-3% and omega-6%).

Results

In our main models, both omega-6% and omega-3% were inversely associated with overall cancer incidence (HR per SD = 0.98, 95% CI = 0.96-0.99; HR per SD = 0.99, 95% CI = 0.97-1.00; respectively). Of the 19 site-specific cancers available, 14 were associated with omega-6% and five with omega-3%, all indicating inverse associations, with the exception that prostate cancer was positively associated with omega-3% (HR per SD = 1.03, 95% CI = 1.01 - 1.05).

Conclusions

Our population-based cohort study in UK Biobank indicates small inverse associations of plasma omega-6 and omega-3 PUFAs with the incidence of overall and most site-specific cancers, although there are notable exceptions, such as prostate cancer.

Serum levels of n-3 PUFA and colorectal cancer risk in Chinese population

Circulating n-3 PUFA, which integrate endogenous and exogenous n-3 PUFA, can be better used to investigate the relationship between n-3 PUFA and disease. However, studies examining the associations between circulating n-3 PUFA and colorectal cancer (CRC) risk were limited, and the results remained inconclusive. This case–control study aimed to examine the association between serum n-3 PUFA and CRC risk in Chinese population. A total of 680 CRC cases and 680 sex- and age-matched (5-year interval) controls were included. Fatty acids were assayed by GC. OR and 95 % CI were calculated using multivariable logistic regression after adjustment for potential confounders. Higher level of serum α-linolenic acid (ALA), docosapentaenoic acid (DPA), DHA, long-chain n-3 PUFA and total n-3 PUFA were associated with lower odds of CRC. The adjusted OR and 95 % CI were 0·34 (0·24, 0·49, Pfor trend < 0·001) for ALA, 0·57 (0·40, 0·80, Pfor trend < 0·001) for DPA, 0·48 (0·34, 0·68, Pfor trend < 0·001) for DHA, 0·39 (0·27, 0·56, Pfor trend < 0·001) for long-chain n-3 PUFA and 0·31 (0·22, 0·45, Pfor trend < 0·001) for total n-3 PUFA comparing the highest with the lowest quartile. However, there was no statistically significant association between EPA and odds of CRC. Analysis stratified by sex showed that ALA, DHA, long-chain n-3 PUFA and total n-3 PUFA were inversely associated with odds of CRC in both sexes. This study indicated that serum ALA, DPA, DHA, long-chain n-3 PUFA and total n-3 PUFA were inversely associated with odds of having CRC in Chinese population.

Food Intake and Colorectal Cancer

Colorectal cancer (CRC) accounts for considerable mortalities worldwide. Several modifiable risk factors, including a high intake of certain foods and beverages can cause CRC. This review summarized the latest findings on the intake of various foods, nutrients, ingredients, and beverages on CRC development, with the objective of classifying them as a risk or protective factor. High-risk food items include red meat, processed meat, eggs, high alcohol consumption, sugar-sweetened beverages, and chocolate candy. Food items that are protective include milk, cheese and other dairy products, fruits, vegetables (particularly cruciferous), whole grains, legumes (particularly soy beans), fish, tea (particularly green tea), coffee (particularly among Asians), chocolate, and moderate alcohol consumption (particularly wine). High-risk nutrients/ingredients include dietary fat from animal sources and industrial trans-fatty acids (semisolid/solid hydrogenated oils), synthetic food coloring, monosodium glutamate, titanium dioxide, and high-fructose corn sirup. Nutrients/ingredients that are protective include dietary fiber (particularly from cereals), fatty acids (medium-chain and odd-chain saturated fatty acids and highly unsaturated fatty acids, including omega-3 polyunsaturated fatty acids), calcium, polyphenols, curcumin, selenium, zinc, magnesium, and vitamins A, C, D, E, and B (particularly B6, B9, and B2). A combination of micronutrients and multi-vitamins also appears to be beneficial in reducing recurrent adenoma incidence.

The effect of FTO gene rs9939609 polymorphism on the association between colorectal cancer and different types of dietary fat intake: a case-control study

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers in the world. Some dietary factors such as fat intake have been identified as the risk factors for CRC. This study aimed to investigate the effect of fat mass and obesity-associated (FTO) gene rs9939609 polymorphism on the association between CRC and different types of dietary fats.

METHODS

This case-control study was performed on 135 CRC cases and 294 healthy controls in Tehran, Iran. Data on demographic factors, anthropometric measurements, physical activity, the intake of different types of dietary fats, and FTO gene rs9939609 polymorphism was collected from all participants. The association between cancer and dietary fat intake in individuals with different FTO genotypes was assessed using different models of logistic regression.

RESULTS

Oleic acid intake was higher in the case group compared to the control group in both people with TT (7.2±3.46 vs. 5.83±3.06 g/d, P=0.02) and AA/AT genotypes (8.7±6.23 vs. 5.57 ±3.2 g/d, P<0.001). Among carriers of AA/AT genotypes of FTO rs9939609 polymorphism, a positive association was found between CRC and higher intakes of oleic acid (OR=1.12, CI95% 1.03-1.21, P=0.01) and cholesterol (OR=1.01, CI95% 1.00-1.02; P=0.01) after adjusting for age, sex, physical activity, alcohol use, smoking, calorie intake, and body mass index.

CONCLUSION

Higher intakes of cholesterol and oleic acid were associated with a higher risk of CRC in FTO-risk allele carriers. The association of CRC and dietary fat may be influenced by the FTO genotype. Further longitudinal studies are warranted to confirm these findings.

Comparative study on nutritional quality and serum biochemical indices of common carp (Cyprinus carpio) aged 11 to 13 months aged cultured in traditional ponds and land-based container aquaculture systems

In the study, the physical characteristics, nutritional composition, mineral elements, volatile substances, and serum biochemistry of common carp (Cyprinus carpio) after rearing for two months were compared and analyzed to reveal the differences in muscle nutritional quality and serum biochemical indices between fish raised in traditional ponds (TP) and land-based container recirculating aquaculture systems (C-RAS). One hundred fish were selected from each aquaculture mode for the following experiments. Results show that: in terms of physical properties, C-RAS frozen seepage rate was significantly lower than that in TP (P < 0.05), the chewiness, gumminess, springiness, resilience, adhesiveness, cohesiveness, and shearing of C-RAS group were significantly higher than in TP (P < 0.01). Regarding muscle nutrients, the moisture, the crude lipid contents of C-RAS group were significantly lower than that of the TP group (P < 0.05), and the crude protein content of C-RAS group was extremely significantly higher than that in TP (P < 0.01). The saturated fatty acids (ΣSFA) and polyunsaturated fatty acids (ΣPUFA) in the muscle of C-RAS were significantly higher than that in TP (P < 0.01), and monounsaturated fatty acids (ΣMUFA) of C-RAS were significantly lower than that in TP (P < 0.01). Methionine content in C-RAS was significantly higher than that in TP (P < 0.05). In terms of mineral elements, the contents of K and Se in C-RAS were significantly higher than those in TP, and the content of Zn in C-RAS was significantly lower than that in TP (P < 0.05). In terms of volatile substances, nonanal, octanal, and benzaldehyde in C-RAS were significantly lower than those in TP(P < 0.01), 2,3-diethyl-5-methylpyrazine, ethyl 3-methylpentanoate, butyl formate were significantly higher than those in TP (P < 0.01). In terms of serum biochemistry, the glucose index in C-RAS was extremely significantly lower than that in TP group, total protein, albumin, alkaline phosphatase, and triglyceride were extremely significantly higher than those in TP (P < 0.01). Experiments show that the aquaculture mode has a large impact on the physical properties of the common carp, nutrients, mineral elements, volatile matter, and serum biochemical. In conclusion, the common carp cultured in C-RAS systems had better muscle nutritional quality, which provides a reference for future regulation of fish nutritional quality by C-RAS.

The association between genetically elevated polyunsaturated fatty acids and risk of cancer

BACKGROUND

The causal relevance of polyunsaturated fatty acids (PUFAs) for risk of site-specific cancers remains uncertain.

METHODS

Using a Mendelian randomization (MR) framework, we assessed the causal relevance of PUFAs for risk of cancer in European and East Asian ancestry individuals. We defined the primary exposure as PUFA desaturase activity, proxied by rs174546 at the FADS locus. Secondary exposures were defined as omega 3 and omega 6 PUFAs that could be proxied by genetic polymorphisms outside the FADS region. Our study used summary genetic data on 10 PUFAs and 67 cancers, corresponding to 562,871 cases and 1,619,465 controls, collected by the Fatty Acids in Cancer Mendelian Randomization Collaboration. We estimated odds ratios (ORs) for cancer per standard deviation increase in genetically proxied PUFA exposures.

FINDINGS

Genetically elevated PUFA desaturase activity was associated (P < 0.0007) with higher risk (OR [95% confidence interval]) of colorectal cancer (1.09 [1.07-1.11]), esophageal squamous cell carcinoma (1.16 [1.06-1.26]), lung cancer (1.06 [1.03-1.08]) and basal cell carcinoma (1.05 [1.02-1.07]). There was little evidence for associations with reproductive cancers (OR = 1.00 [95% CI: 0.99-1.01]; Pheterogeneity = 0.25), urinary system cancers (1.03 [0.99-1.06], Pheterogeneity = 0.51), nervous system cancers (0.99 [0.95-1.03], Pheterogeneity = 0.92) or blood cancers (1.01 [0.98-1.04], Pheterogeneity = 0.09). Findings for colorectal cancer and esophageal squamous cell carcinoma remained compatible with causality in sensitivity analyses for violations of assumptions. Secondary MR analyses highlighted higher omega 6 PUFAs (arachidonic acid, gamma-linolenic acid and dihomo-gamma-linolenic acid) as potential mediators. PUFA biosynthesis is known to interact with aspirin, which increases risk of bleeding and inflammatory bowel disease. In a phenome-wide MR study of non-neoplastic diseases, we found that genetic lowering of PUFA desaturase activity, mimicking a hypothetical intervention to reduce cancer risk, was associated (P < 0.0006) with increased risk of inflammatory bowel disease but not bleeding.

INTERPRETATION

The PUFA biosynthesis pathway may be an intervention target for prevention of colorectal cancer and esophageal squamous cell carcinoma but with potential for increased risk of inflammatory bowel disease.

FUNDING

Cancer Resesrch UK (C52724/A20138, C18281/A19169). UK Medical Research Council (MR/P014054/1). National Institute for Health Research (NIHR202411). UK Medical Research Council (MC_UU_00011/1, MC_UU_00011/3, MC_UU_00011/6, and MC_UU_00011/4). National Cancer Institute (R00 CA215360). National Institutes of Health (U01 CA164973, R01 CA60987, R01 CA72520, U01 CA74806, R01 CA55874, U01 CA164973 and U01 CA164973).

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.

Effects of Submerged Macrophytes on the Growth, Morphology, Nutritional Value, and Flavor of Cultured Largemouth Bass (Micropterus salmoides)

Aquaculture environment plays important roles in regulating the growth, morphology, nutrition, and flavor of aquatic products. The present study investigated growth, morphology, nutrition, and flavor formation in largemouth bass (Micropterus salmoides) cultured in the ponds with (EM group) and without (M group) the submerged macrophytes (Elodea nuttallii). Fish in the EM group showed a significantly greater body length, higher growth rate, and lower hepatosomatic index than those in the M group (p< 0.05). Moreover, compared with fish in the M group, those in the EM group showed improved muscle quality with significantly elevated levels of crude protein, total free and hydrolysable amino acids, and polyunsaturated fatty acids (p < 0.05). Specifically, certain amino acids related to flavor (Glu, Asp, Ala, and Arg) and valuable fatty acids (C18:2, C18:3n3, C20:3n3, and C22:6) were more abundant in the EM group (p < 0.05). In addition, the levels of 19 volatile (p < 0.05) were significantly higher in the EM group than in the M group. Therefore, E. nuttallii significantly improved growth, morphological traits, nutritional components, and characteristic flavor in largemouth bass, indicating the superior nutritional value and palatability of fish cultured with submerged macrophytes.

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.

Omega-3 fatty acid supplementation and fecundability

STUDY QUESTION

Is self-reported use of omega-3 fatty acid supplements associated with fecundability, the probability of natural conception, in a given menstrual cycle?

SUMMARY ANSWER

Prospectively recorded omega-3 supplement use was associated with an increased probability of conceiving.

WHAT IS KNOWN ALREADY

In infertile women, omega-3 fatty acid intake has been associated with increased probability of pregnancy following IVF. In natural fertility, studies are conflicting, and no study of natural fertility has evaluated omega-3 fatty acid supplementation and fecundity.

STUDY DESIGN, SIZE, DURATION

Secondary data analysis of 900 women contributing 2510 cycles in Time to Conceive (TTC), a prospective, time to pregnancy cohort study from 2008 to December 2015.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women aged 30-44 years, trying to conceive <3 months, without history of infertility were followed using standardized pregnancy testing. While attempting to conceive, women daily recorded menstrual cycle events and supplement and medication intake using the Cerner Multum Drug Database. Supplements and vitamins containing omega-3 were identified. Omega-3 use, defined as use in at least 20% of days in a given menstrual cycle, in each pregnancy attempt cycle was determined. A discrete-time Cox proportional hazards model was used to calculate the fecundability ratio.

MAIN RESULTS AND THE ROLE OF CHANCE

Women taking omega-3 supplementation were more likely to be younger, thinner, nulligravid, white and to take vitamin D, prenatal and multivitamins compared to women not taking omega-3s. After adjusting for age, obesity, race, previous pregnancy, vitamin D and prenatal and multivitamin use, women taking omega-3 supplements had 1.51 (95% CI 1.12, 2.04) times the probability of conceiving compared to women not taking omega-3s.

LIMITATIONS, REASONS FOR CAUTION

Our study was not a randomized controlled trial. The women who used omega-3 supplements may represent a more health-conscious population. We sought to address this by adjusting for multiple factors in our model. Additionally, the omega-3 fatty acid supplements that TTC participants used included multiple types and brands with varying dosages of omega-3 fatty acids. Women reported the type of supplement they were taking but not the concentration of omega-3s in that supplement. It is therefore not possible to compare dosing or a dose-response relationship in our study.

WIDER IMPLICATIONS OF THE FINDINGS

Omega-3 supplementation may present a feasible and inexpensive modifiable factor to improve fertility. Randomized controlled trials are needed to further investigate the benefits of omega-3 supplementation for women trying to conceive naturally.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by the Division of Reproductive Endocrinology and Infertility at the University of North Carolina at Chapel Hill, the NIH/NICHD (R21 HD060229-01 and R01 HD067683-01), and in part by the Intramural Research Program of the National Institute of Environmental Health Sciences (Z01ES103333). The authors declare that there is no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Omega-3 polyunsaturated fatty acids: moving towards precision use for prevention and treatment of colorectal cancer

Data from experimental studies have demonstrated that marine omega-3 polyunsaturated fatty acids (O3FAs) have anti-inflammatory and anticancer properties. In the last decade, large-scale randomised controlled trials of pharmacological delivery of O3FAs and prospective cohort studies of dietary O3FA intake have continued to investigate the relationship between O3FA intake and colorectal cancer (CRC) risk and mortality. Clinical data suggest that O3FAs have differential anti-CRC activity depending on several host factors (including pretreatment blood O3FA level, ethnicity and systemic inflammatory response) and tumour characteristics (including location in the colorectum, histological phenotype (eg, conventional adenoma or serrated polyp) and molecular features (eg, microsatellite instability, cyclooxygenase expression)). Recent data also highlight the need for further investigation of the effect of O3FAs on the gut microbiota as a possible anti-CRC mechanism, when used either alone or in combination with other anti-CRC therapies. Overall, these data point towards a precision approach to using O3FAs for optimal prevention and treatment of CRC based on mechanistic understanding of host, tumour and gut microbiota factors that predict anticancer activity of O3FAs.

Fish Consumption and Colorectal Cancer Risk: Meta-Analysis of Prospective Epidemiological Studies and Review of Evidence from Animal Studies

Background: Epidemiological studies on the association between fish consumption and colorectal cancer (CRC) risk have yielded inconsistent results, despite evidence from preclinical studies that long-chain ω-3 polyunsaturated fatty acids inhibit colorectal carcinogenesis. We conducted a meta-analysis of prospective epidemiological studies investigating the association between fish consumption and CRC risk among humans and reviewed studies examining the link between fish components and colorectal carcinogenesis in animal models. Methods: We included studies published until November 2020. We calculated the summary risk ratio (SRR) and 95% confidence intervals (CI) through random effects meta-analysis models in order to summarize evidence from studies among humans. Results: Twenty-five prospective epidemiological studies encompassing 25,777 CRC cases were included. Individuals in the highest (vs. lowest) category of fish consumption had a significantly reduced risk of CRC (SRR 0.94, 95%CI 0.89-0.99). In dose-response meta-analysis, a 50-g increment in the daily consumption of fish was associated with a statistically significant 4% reduction in CRC risk (SRR 0.96, 95%CI 0.92-0.99). Preclinical studies (n = 25) identified multiple mechanisms of action of fish and fish components on colorectal carcinogenesis. Conclusions: Dietary recommendations for cancer prevention should take into account the evidence from epidemiological and preclinical studies that increasing fish consumption may be effective in preventing CRC.

Nutritional Interventions for Patients with Melanoma: From Prevention to Therapy-An Update

Melanoma is an aggressive skin cancer, whose incidence rates have increased over the past few decades. Risk factors for melanoma are both intrinsic (genetic and familiar predisposition) and extrinsic (environment, including sun exposure, and lifestyle). The recent advent of targeted and immune-based therapies has revolutionized the treatment of melanoma, and research is focusing on strategies to optimize them. Obesity is an established risk factor for several cancer types, but its possible role in the etiology of melanoma is controversial. Body mass index, body surface area, and height have been related to the risk for cutaneous melanoma, although an 'obesity paradox' has been described too. Increasing evidence suggests the role of nutritional factors in the prevention and management of melanoma. Several studies have demonstrated the impact of dietary attitudes, specific foods, and nutrients both on the risk for melanoma and on the progression of the disease, via the effects on the oncological treatments. The aim of this narrative review was to summarize the main literature results regarding the preventive and therapeutic role of nutritional schemes, specific foods, and nutrients on melanoma incidence and progression.

Red Blood Cell Fatty Acids and Risk of Colorectal Cancer in The European Prospective Investigation into Cancer and Nutrition (EPIC)

BACKGROUND

A growing body of evidence suggests that alterations of dietary fatty acid (FA) profiles are associated with colorectal cancer risk. However, data from large-scale epidemiologic studies using circulating FA measurements to objectively assess individual FA and FA categories are scarce.

METHODS

We investigate the association between red blood cell (RBC) membrane FAs and risk of colorectal cancer in a case-control study nested within a large prospective cohort. After a median follow-up of 6.4 years, 1,069 incident colorectal cancer cases were identified and matched to 1,069 controls among participants of the European Prospective Investigation into Cancer and Nutrition (EPIC). The FA composition of RBC phospholipids (in mol%) was analyzed by gas chromatography, and their association with risk of colorectal cancer was estimated by multivariable adjusted conditional logistic regression models.

RESULTS

After correction for multiple testing, subjects with higher concentrations of RBC stearic acid were at higher risk for colorectal cancer (OR = 1.23; 95% CI = 1.07-1.42, per 1 mol%). Conversely, colorectal cancer incidence decreased with increasing proportions of RBC n-3 PUFA, particularly eicosapentaenoic acid (0.75; 0.62-0.92, per 1 mol%). The findings for the n-6 PUFA arachidonic acid were inconsistent.

CONCLUSIONS

The positive association between prediagnostic RBC stearic acid and colorectal cancer reflects putative differences in FA intake and metabolism between cancer cases and matched controls, which deserve further investigation. The inverse relationship between EPA and colorectal cancer is in line with the repeatedly reported protective effect of fish consumption on colorectal cancer risk.

IMPACT

These findings add to the evidence on colorectal cancer prevention.

Total Dietary Fat Intake, Fat Quality, and Health Outcomes: A Scoping Review of Systematic Reviews of Prospective Studies

INTRODUCTION

We conducted a scoping review of systematic reviews (SRs) on dietary fat intake and health outcomes in human adults within the context of a position paper by the "International Union of Nutritional Sciences Task force on Dietary Fat Quality" tasked to summarize the available evidence and provide dietary recommendations.

METHODS

We systematically searched several databases for relevant SRs of randomized controlled trials (RCTs) and/or prospective cohort studies published between 2015 and 2019 assessing the association between dietary fat and health outcomes.

RESULTS

Fifty-nine SRs were included. The findings from SRs of prospective cohort studies, which frequently compare the highest versus lowest intake categories, found mainly no association of total fat, monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), and saturated fatty acid (SFA) with risk of chronic diseases. SRs of RCTs applying substitution analyses indicate that SFA replacement with PUFA and/or MUFA improves blood lipids and glycemic control, with the effect of PUFA being more pronounced. A higher intake of total trans-fatty acid (TFA), but not ruminant TFA, was probably associated with an increased risk of mortality and cardiovascular disease based on existing SRs.

CONCLUSION

Overall, the available published evidence deems it reasonable to recommend replacement of SFA with MUFA and PUFA and avoidance of consumption of industrial TFA.

Associations among Dietary Omega-3 Polyunsaturated Fatty Acids, the Gut Microbiota, and Intestinal Immunity

Omega-3 polyunsaturated fatty acids (omega-3 PUFAs), which are essential fatty acids that humans should obtain from diet, have potential benefits for human health. In addition to altering the structure and function of cell membranes, omega-3 PUFAs (docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA), and docosapentaenoic acid (DPA)) exert different effects on intestinal immune tolerance and gut microbiota maintenance. Firstly, we review the effect of omega-3 PUFAs on gut microbiota. And the effects of omega-3 PUFAs on intestinal immunity and inflammation were described. Furthermore, the important roles of omega-3 PUFAs in maintaining the balance between gut immunity and the gut microbiota were discussed. Additional factors, such as obesity and diseases (NAFLD, gastrointestinal malignancies or cancer, bacterial and viral infections), which are associated with variability in omega-3 PUFA metabolism, can influence omega-3 PUFAs–microbiome–immune system interactions in the intestinal tract and also play roles in regulating gut immunity. This review identifies several pathways by which the microbiota modulates the gut immune system through omega-3 PUFAs. Omega-3 supplementation can be targeted to specific pathways to prevent and alleviate intestinal diseases, which may help researchers identify innovative diagnostic methods.

Colon Carcinogenesis: The Interplay Between Diet and Gut Microbiota

Colorectal cancer (CRC) incidence increases yearly, and is three to four times higher in developed countries compared to developing countries. The well-known risk factors have been attributed to low physical activity, overweight, obesity, dietary consumption including excessive consumption of red processed meats, alcohol, and low dietary fiber content. There is growing evidence of the interplay between diet and gut microbiota in CRC carcinogenesis. Although there appears to be a direct causal role for gut microbes in the development of CRC in some animal models, the link between diet, gut microbes, and colonic carcinogenesis has been established largely as an association rather than as a cause-and-effect relationship. This is especially true for human studies. As essential dietary factors influence CRC risk, the role of proteins, carbohydrates, fat, and their end products are considered as part of the interplay between diet and gut microbiota. The underlying molecular mechanisms of colon carcinogenesis mediated by gut microbiota are also discussed. Human biological responses such as inflammation, oxidative stress, deoxyribonucleic acid (DNA) damage can all influence dysbiosis and consequently CRC carcinogenesis. Dysbiosis could add to CRC risk by shifting the effect of dietary components toward promoting a colonic neoplasm together with interacting with gut microbiota. It follows that dietary intervention and gut microbiota modulation may play a vital role in reducing CRC risk.

Interactions between environmental pollutants and dietary nutrients: current evidence and implications in epidemiological research

Environmental pollutants and nutrients may be present in the same foodstuffs or dietary patterns; share internal mechanisms of transport, metabolism and cellular uptake; or target the same molecular signalling pathways and biological functions. Lipophilic pollutants and nutrients, like dioxins and polyunsaturated fatty acids, may often converge at all aforementioned levels and thus the interactions become more likely. Despite this fact, the topic seems overlooked in mainstream epidemiological research. In this essay, we illustrate different levels of documented interactions between pollutants and nutrients with experimental, interventional and epidemiological evidence, paying special attention to lipophilic chemicals. We first describe common pollutants and nutrients encountered in diets and the internal lipophilic interface such as adipose tissue and serum lipids. Next, we discuss the preventive effects of nutrients against absorption and the toxic effects of pollutants, as well as the pollutant-induced perturbation of nutrient metabolism. Finally, we discuss the implications of nutrient-pollutant interactions in epidemiology, providing some examples of negative confounding, modification effect and statistical interactions reported for different outcomes including fetal growth, diabetes and cancer. The evidence discussed in this essay supports that the health impacts of chemicals have likely been underestimated due to the high risk of residual and coexposure confounding in diseases where interactions between pollutants and nutrients may occur.

Reduction of Polyunsaturated Fatty Acids with Tumor Progression in a Lean Non-Alcoholic Steatohepatitis-Associated Hepatocellular Carcinoma Mouse Model

Background and Aim: Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in Western countries. While obesity and diabetes are the hallmarks of NAFLD, it also develops in lean individuals in the absence of metabolic syndrome, with a prevalence of 7 percent in the U.S. and 25-30 percent in some Asian countries. NAFLD represents the spectrum of liver disease, starting with excess liver fat accumulation (NAFL) that can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and ultimately hepatocellular carcinoma (HCC). To date, the pathogenesis of lean NASH-HCC is poorly understood and a mouse model is lacking. We aimed to develop a mouse model of lean NASH-HCC using a choline deficient and high trans-fat/sucrose/cholesterol diet to enable better understanding of its molecular pathogenesis. Methods: C57BL/6N mice were fed this diet starting at 4 weeks of age for 52 weeks and were compared to mice fed an isocaloric low fat control diet for the same duration. C57BL/6N mice were chosen instead of the C57BL/6J mice due to the high susceptibility of C57BL/6J mice to diet-induced obesity. The plasma and tumor fatty acid profile of these mice was also investigated. Results: Nearly 61% of the mice developed lean NASH-HCC. These mice showed reduction of plasma polyunsaturated fatty acids (PUFAs) (linolenic acids (α and γ, ω-3 and ω-6, respectively), eicosapentanoic acid (ω-3), docosahexanoic acid (ω-3), and linoleic acid (ω-6)) and increasing levels over time in mice with pre-malignant lesions. Conclusions: We developed a novel high penetrance diet-induced lean NASH-HCC mouse model. Plasma PUFA levels were reduced with tumor progression in parallel with reduced expression of genes controlling desaturase expression suggesting their potential use as biomarkers for lean NASH-HCC progression as well as chemopreventive molecules.

Objectively-Measured Light-Intensity Physical Activity and Risk of Cancer Mortality: A Meta-analysis of Prospective Cohort Studies

BACKGROUND

The impact of light-intensity physical activity (LPA) in preventing cancer mortality has been questioned. To address this concern, the present meta-analysis aimed to quantify the association between objectively-measured LPA and risk of cancer mortality.

METHODS

We conducted a systematic literature search in PubMed and Scopus to January 2020. Prospective cohort studies reporting the association between objectively-measured LPA using activity monitors (e.g., accelerometers) and risk of cancer mortality in the general population were included. The summary hazard ratios (HR) per 30 min/day of LPA and 95% confidence intervals (CI) were obtained using a random-effects model. Dose-response analysis was used to plot their relationship.

RESULTS

Five prospective cohort studies were included, in which the definition of LPA based on accelerometer readings was mainly set within 100 to 2,100 counts/min. The summary HR for cancer mortality per 30 min/day of LPA was 0.86 (95% CI, 0.79-0.95; I ² < 1%), and the association between LPA and risk reduction in cancer mortality was linearly shaped (P _nonlinearity = 0.72). LPA exhibited a comparable magnitude of risk reduction in cancer mortality of moderate-to-vigorous physical activity regardless of equal time-length (0.87 per 30 min/day vs. 0.94 per 30 min/day, P _interaction = 0.46) or equal amount (0.74 vs. 0.94 per 150 metabolic equivalents-min/day, P _interaction = 0.11). Furthermore, replacing sedentary time by LPA of 30 min/day decreased the risk of cancer mortality by 9%.

CONCLUSIONS

Objectively-measured LPA conferred benefits in decreasing the risk of cancer mortality.

IMPACT

LPA should be considered in physical activity guidelines to decrease the risk of cancer mortality.