Quantification of Urinary Phenyl-γ-Valerolactones and Related Valeric Acids in Human Urine on Consumption of Apples

Flavan-3-ols are dietary bioactive molecules that have beneficial effects on human health and reduce the risk of various diseases. Monomeric flavan-3-ols are rapidly absorbed in the small intestine and released in the blood stream as phase II conjugates. Polymeric flavan-3-ols are extensively metabolized by colonic gut microbiota into phenyl-γ-valerolactones and their related phenylvaleric acids. These molecules are the main circulating metabolites in humans after the ingestion of flavan-3-ol rich-products; nevertheless, they have received less attention and their role is not understood yet. Here, we describe the quantification of 8 phenyl-γ-valerolactones and 3 phenylvaleric acids in the urine of 11 subjects on consumption of apples by using UHPLC-ESI-Triple Quad-MS with pure reference compounds. Phenyl-γ-valerolactones, mainly as sulfate and glucuronic acid conjugates, reached maximum excretion between 6 and 12 after apple consumption, with a decline thereafter. Significant differences were detected in the cumulative excretion rates within subjects and in the ratio of dihydroxyphenyl-γ-valerolactone sulfate to glucuronide conjugates. This work observed for the first time the presence of two distinct metabotypes with regards to the excretion of phenyl-γ-valerolactone phase II conjugates.

The ellagitannin metabolite urolithin C is a glucose-dependent regulator of insulin secretion through activation of L-type calcium channels

BACKGROUND AND PURPOSE

The pharmacology of polyphenol metabolites on beta-cell function is largely undetermined. We sought to identify polyphenol metabolites that enhance the insulin-secreting function of beta-cells and to explore the underlying mechanisms.

EXPERIMENTAL APPROACH

INS-1 beta-cells and rat isolated islets of Langerhans or perfused pancreas preparations were used for insulin secretion experiments. Molecular modelling, intracellular Ca2+ monitoring, and whole-cell patch-clamp recordings were used for mechanistic studies.

KEY RESULTS

Among a set of polyphenol metabolites, we found that exposure of INS-1 beta-cells to urolithins A and C enhanced glucose-stimulated insulin secretion. We further characterized the activity of urolithin C and its pharmacological mechanism. Urolithin C glucose-dependently enhanced insulin secretion in isolated islets of Langerhans and perfused pancreas preparations. In the latter, enhancement was reversible when glucose was lowered from a stimulating to a non-stimulating concentration. Molecular modelling suggested that urolithin C could dock into the Cav 1.2 L-type Ca2+ channel. Calcium monitoring indicated that urolithin C had no effect on basal intracellular Ca2+ but enhanced depolarization-induced increase in intracellular Ca2+ in INS-1 cells and dispersed cells isolated from islets. Electrophysiology studies indicated that urolithin C dose-dependently enhanced the L-type Ca2+ current for levels of depolarization above threshold and shifted its voltage-dependent activation towards more negative potentials in INS-1 cells.

CONCLUSION AND IMPLICATIONS

Urolithin C is a glucose-dependent activator of insulin secretion acting by facilitating L-type Ca2+ channel opening and Ca2+ influx into pancreatic beta-cells. Our work paves the way for the design of polyphenol metabolite-inspired compounds aimed at ameliorating beta-cell function.

Critical and emerging topics in dietary carbohydrates and health

Multiple factors may affect the metabolic fate of carbohydrates. Today, well-standardised and accepted methods may allow for the definitions of the changes in the glucose and insulin curves following the ingestion of either carbohydrate-based and other foods. More debate is still raised on the clinical meaning of these classifications when used at a population level, while emphasis is raised on the approach to carbohydrate metabolism on an individual basis. Within these ranges of applications, other compounds, such as plant polyphenols, may favourably add synergic effects through the modulation of carbohydrate digestion and glucose metabolic steps, resulting in lowering postprandial glucose and insulin levels. Finally, a growing knowledge suggests that the balance of dietary fructose and individual physical activity represent the key point to address the compound towards either positive, energy sparing effects, or a degenerative metabolic burden. The carbohydrate quality within a whole dietary and lifestyle pattern may therefore challenge the individual balance towards health or disease.

Egg consumption and human health: an umbrella review of observational studies

Egg consumption has been an area of controversy regarding its impact on human health largely due to the content in cholesterol and its potential role in cardio-metabolic outcomes. This study aimed to summarise the level of evidence of egg consumption on various health outcomes. A systematic search for meta-analyses was performed: study design, dose-response relationship, heterogeneity and agreement of results over time, and identification of potential confounding factors were considered to assess the level of evidence. Results from this umbrella review showed a substantial no association between egg consumption and a number of health outcomes, including cancer, cardiovascular and metabolic disorders. In contrast, evidence of possible beneficial effects toward stroke risk has been found. In conclusions, egg may be part of a healthy diet; however, additional studies exploring confounding factors are needed to ascertain the potential detrimental effects.

Dairy foods and health: an umbrella review of observational studies

Evidence on consumption of dairy foods and human health is contradictory. This study aimed to summarize the level of evidence of dairy consumption on various health outcomes. A systematic search for meta-analyses was performed: study design, dose-response relationship, heterogeneity and agreement of results over time, and identification of potential confounding factors were considered to assess the level of evidence. Convincing and probable evidence of decreased risk of colorectal cancer, hypertension and cardiovascular disease, elevated blood pressure and fatal stroke, respectively, was found for total dairy consumption; possible decreased risk of breast cancer, metabolic syndrome, stroke and type-2 diabetes, and increased risk of prostate cancer and Parkinson's disease was also found. Similar, yet not entirely consistent evidence for individual dairy products was reported. Among potential confounding factors, geographical localisation and fat content of dairy have been detected. In conclusions, dairy may be part of a healthy diet; however, additional studies exploring confounding factors are needed to ascertain the potential detrimental effects.

Pomegranate juice to reduce fecal calprotectin levels in inflammatory bowel disease patients with a high risk of clinical relapse: Study protocol for a randomized controlled trial

Background

Inflammatory bowel disease (IBD) is a chronic condition characterized by recurrent episodes of intestinal inflammation and is thought to be related to an autoimmune reaction to genetic and environmental factors. Although evidence indicates that a polyphenolic-rich diet plays an important role in modulating aspects of chronic inflammation, few studies have focused on the effect of ellagitannin (ET)-rich food consumption on long-term remission maintenance in IBD patients with a high risk of clinical relapse. Therefore, we hypothesize that supplementation with a pomegranate juice, a naturally rich source of ETs, could significantly modulate the markers of mucosal and systemic inflammation relative to a control group receiving a placebo.

Methods/design

This double-blind, randomized controlled trial includes patients with IBD involving the colorectum who have been in stable therapy for at least the three previous months and have a high risk of clinical relapse. Participants are randomly allocated to one of two groups: active supplementation (125 mL of cv. Wonderful pomegranate juice) or placebo (125 mL) taken twice daily for 12 weeks. The primary outcome is changes in the fecal neutrophil-derived protein calprotectin, a surrogate marker of mucosal improvement, between the two groups from baseline to 12 weeks later. The secondary outcomes include transcriptomic changes in peripheral blood mononuclear cells and intestinal biopsies and changes in circulating inflammatory markers and trimethylamine-N-oxide levels. Pomegranate ET-derived metabolites are identified and quantified in plasma and urine samples.

Discussion

The results will provide information on the possible reduction of fecal calprotectin levels following the consumption of pomegranate juice. The findings will also show the in vivo metabolism of pomegranate ETs. Finally, the effect of 12-week pomegranate juice consumption on local and systemic inflammatory markers will be elucidated, which will likely provide additional insights into the maintenance of remission in IBD patients.

Trial registration

ClinicalTrials.gov, NCT03000101. Registered on 21 December 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3321-8) contains supplementary material, which is available to authorized users.

Inter-individual variability in the production of flavan-3-ol colonic metabolites: preliminary elucidation of urinary metabotypes

PURPOSE

There is much information on the bioavailability of (poly)phenolic compounds following acute intake of various foods. However, there are only limited data on the effects of repeated and combined exposure to specific (poly)phenol food sources and the inter-individual variability in their bioavailability. This study evaluated the combined urinary excretion of (poly)phenols from green tea and coffee following daily consumption by healthy subjects in free-living conditions. The inter-individual variability in the production of phenolic metabolites was also investigated.

METHODS

Eleven participants consumed both tablets of green tea and green coffee bean extracts daily for 8 weeks and 24-h urine was collected on five different occasions. The urinary profile of phenolic metabolites and a set of multivariate statistical tests were used to investigate the putative existence of characteristic metabotypes in the production of flavan-3-ol microbial metabolites.

RESULTS

(Poly)phenolic compounds in the green tea and green coffee bean extracts were absorbed and excreted after simultaneous consumption, with green tea resulting in more inter-individual variability in urinary excretion of phenolic metabolites. Three metabotypes in the production of flavan-3-ol microbial metabolites were tentatively defined, characterized by the excretion of different amounts of trihydroxyphenyl-γ-valerolactones, dihydroxyphenyl-γ-valerolactones, and hydroxyphenylpropionic acids.

CONCLUSIONS

The selective production of microbiota-derived metabolites from flavan-3-ols and the putative existence of characteristic metabotypes in their production represent an important development in the study of the bioavailability of plant bioactives. These observations will contribute to better understand the health effects and individual differences associated with consumption of flavan-3-ols, arguably the main class of flavonoids in the human diet.

Dietary Polyphenol Intake, Blood Pressure, and Hypertension: A Systematic Review and Meta-Analysis of Observational Studies

Background: Dietary polyphenols, including flavonoids, have been the focus of major recent attentions due to their wide content in a variety of foods commonly consumed and the findings from numerous studies showing evidence of an association with positive outcomes on human health. Methods: A systematic search using electronic databases PubMed and EMBASE was performed to retrieve English language studies published from the earliest indexing year of each database to April 2019, reporting on the association between dietary flavonoids intake and hypertension. Results: The search strategy resulted in the final selection of 20 studies including 15 cross-sectional investigations and 7 prospective cohorts (1 study reported on 3 prospective cohorts). 5 prospective cohorts, comprising 200,256 individuals and 45,732 cases of hypertension were included in the quantitative analysis. Analysis by extreme quantiles of intake of flavonoid showed a non-significant association with decreased risk of hypertension (RR (risk ratio): 0.96, 95% CI (confidence interval): 0.89, 1.03). Taking into consideration individual flavonoid subclasses, dietary anthocyanins intake was associated with 8% reduction in risk of hypertension, when comparing highest vs. lowest exposure (RR: 0.92, 95% CI: 0.88, 0.97). Conclusions: Further studies are needed to strengthen the retrieved association between anthocyanins consumption and decreased risk of hypertension and clarify whether total flavonoids or rather individual subclasses may exert beneficial effects on blood pressure.

An in vitro exploratory study of dietary strategies based on polyphenol-rich beverages, fruit juices and oils to control trimethylamine production in the colon

Trimethylamine-N-oxide (TMAO) has been described as a new biomarker of cardiovascular disease (CVD), derived from gut microbial biotransformation of dietary choline and l-carnitine into trimethylamine (TMA) and subsequent hepatic oxidation. (Poly)phenols are among the dietary factors able to interfere with microbial enzymatic activity, possibly modulating TMA biotransformation at the gut level. The aim of this work was to investigate the in vitro biotransformation of choline and carnitine using faecal starters obtained from omnivorous and vegetarian subjects and the effect of (poly)phenol-rich foods on TMA production. Choline and l-carnitine were fermented with vegetarian or omnivorous faecal slurries, alone or in combination with 10 (poly)phenol-rich food items. TMA production from carnitine, but not from choline, was significantly lower when vegetarian faecal starters were used and, among the tested food items, blonde orange juice significantly reduced TMA formation during faecal biotransformation. Consequently, the main compounds of orange juice, namely phenolic compounds, terpenes, limonoids, organic acids and sugars, were tested individually. Sugars exerted the highest inhibitory effect on TMA production. Despite some limitations deriving from the applied in vitro model, this is the first work describing a possible role of some (poly)phenol-rich dietary products on the modulation of TMA colonic production. Free sugars were the main factor responsible for TMA inhibition, suggesting a potential beneficial role of colonic fermentation of carbohydrates in reducing TMA formation from its precursor molecules. This work opens new research directions to evaluate the effect of dietary fermentable fibre on TMA production and, potentially, on circulating TMAO levels.

Fruit and vegetable consumption and health outcomes: an umbrella review of observational studies

The aim of this study was to provide a comprehensive evaluation of current evidence on fruit and vegetable consumption and health outcomes. A systematic search for quantitative syntheses was performed. Several criteria, including study design, dose-response relationship, heterogeneity and agreement of results over time, and identification of potential confounding factors, were used to assess the level of evidence. The strongest (probable) evidence was found for cardiovascular disease protection; possible evidence for decreased risk of colon cancer, depression and pancreatic diseases was found for fruit intake; and colon and rectal cancer, hip fracture, stroke, depression and pancreatic diseases was found for vegetable intake. Suggestive and rather limited associations with other outcomes have been found. Evidence of potential confounding by sex and geographical localisation has been reported. Despite findings are consistent enough for hypothesising causation (at least for cardiovascular-related outcomes), further studies are needed to clarify the role of potential confounding factors.

Dark chocolate modulates platelet function with a mechanism mediated by flavan-3-ol metabolites

Cocoa is a rich source bioactive compounds, i.e., flavan-3-ols, and its consumption has been associated with several beneficial effects, such as the positive modulation of the hemostasis targeted by the platelet function. However, these phenolic compounds have a very low bioavailability and extensively undergo phase I and II metabolism, with the appearing into the bloodstream of (epi)catechin conjugates and phenyl-γ-valerolactones and their conjugates, at different times.The aims of this study were to explore the effect of dark chocolate on platelet function and to investigate the relationship between this interplay and flavan-3-ol derived metabolites.Eighteen healthy male volunteers ingested 50 g of 90% cocoa chocolate within 5 minutes. Blood samples were collected immediately before chocolate ingestion (T0) and 4 hours afterwards (T1). Platelet function analyzer (PFA)-100 closure time was assessed using collagen/adenosine-5'-diphosphate (COL/ADP) and collagen/epinephrine (COL/EPI) cartridges. Plasma flavan-3-ol metabolites were identified and quantified by means of liquid chromatography coupled to a triple quadrupole mass spectrometer (UHPLC-ESI-MS/MS).Results evidenced a significant increase of COL/ADP-induced PFA-100 closure time, but not COL/EPI, 4 hours after ingestion of dark chocolate. Total plasma structurally-related (epi)catechin metabolite (SREM) concentration significantly increased at T1, together with 4 out of the 6 detected metabolites. Total phenyl-γ-valerolactone concentrations remained unchanged. Spearman correlations evidenced a strong correlation between COL/ADP closure time and SREMs, mainly led by (epi)catechin-sulfate isomers.These data confirm that the potential beneficial effect of dark chocolate on primary hemostasis may be mediated by flavan-3-ol circulating metabolites.

Understanding the gut-kidney axis in nephrolithiasis: an analysis of the gut microbiota composition and functionality of stone formers

OBJECTIVES

The involvement of the gut microbiota in the pathogenesis of calcium nephrolithiasis has been hypothesised since the discovery of the oxalate-degrading activity of Oxalobacter formigenes, but never comprehensively studied with metagenomics. The aim of this case-control study was to compare the faecal microbiota composition and functionality between recurrent idiopathic calcium stone formers (SFs) and controls.

DESIGN

Faecal samples were collected from 52 SFs and 48 controls (mean age 48±11). The microbiota composition was analysed through 16S rRNA microbial profiling approach. Ten samples (five SFs, five controls) were also analysed with deep shotgun metagenomics sequencing, with focus on oxalate-degrading microbial metabolic pathways. Dietary habits, assessed through a food-frequency questionnaire, and 24-hour urinary excretion of prolithogenic and antilithogenic factors, including calcium and oxalate, were compared between SFs and controls, and considered as covariates in the comparison of microbiota profiles.

RESULTS

SFs exhibited lower faecal microbial diversity than controls (Chao1 index 1460±363vs 1658±297, fully adjusted p=0.02 with stepwise backward regression analysis). At multivariate analyses, three taxa (Faecalibacterium, Enterobacter, Dorea) were significantly less represented in faecal samples of SFs. The Oxalobacter abundance was not different between groups. Faecal samples from SFs exhibited a significantly lower bacterial representation of genes involved in oxalate degradation, with inverse correlation with 24-hour oxalate excretion (r=-0.87, p=0.002). The oxalate-degrading genes were represented in several bacterial species, whose cumulative abundance was inversely correlated with oxaluria (r=-0.85, p=0.02).

CONCLUSIONS

Idiopathic calcium SFs exhibited altered gut microbiota composition and functionality that could contribute to nephrolithiasis physiopathology.

The Influence of Viable Cells and Cell-Free Extracts of Lactobacillus casei on Volatile Compounds and Polyphenolic Profile of Elderberry Juice

In this study, four strains of Lactobacillus casei, as viable cells or cell-free extracts (CFE), were added to elderberry juice in order to evaluate their effect on phenolic and aromatic profile. Two of them were able to grow in juice while the others showed zero-growth. The same strains were lysed and added as extracts in elderberry juice. Multivariate statistical analysis show a separation among samples containing growing cells, non-growing cells, CFE, highlighting the particularities of specific strains. Juices added with CFE presented the highest amount of esters. The strains showing growth phenotype cause an increase of phenyllactic acids. The highest concentration of volatile compounds, particularly of alcohols, terpenes and norisoprenoids (responsible for typical elderberry notes) was observed in samples with strains showing zero-growth. Moreover, a significant increase in anthocyanin content was observed in these samples, suggesting the possible use of Lactobacillus for increasing specific molecules, even for non-multiplying bacterial cell. Considering that this is the first study concerning the use of non-growing cells in fruit juice, the potential of strains is still to be explored and it may have a significant technological application in the development of a microbial collection useful for fruit juice industry.

Presence of cyclopropane fatty acids in foods and estimation of dietary intake in the Italian population

Cyclopropane fatty acids (CPFAs) are the most abundant cyclic fatty acids in microorganisms with unknown role(s) regarding their dietary relevance and biological effects in humans. This work was aimed to draw up a list of CPFAs-containing foods for estimating their dietary intake in the Italian population to provide a basis for evaluating their nutritional relevance and potential health-related effects. The CPFAs content of more than 500 food items was investigated and a preliminary dietary intake was assessed (12.0 ± 6.0 mg/day), based on the data reported by the Italian National Food Consumption Survey INRAN-SCAI 2005-06. CPFAs should be considered of dietary relevance in view of their potential physiological activity in humans and their presence in significant amounts in dairy products, as Grana Padano cheese (9.0-30.0 mg/100 g), and in bovine meat (0.7-4.0 mg/100 g). Future studies should elucidate whether this uncommon class of fatty acids has a biological role in human health.

Dietary intake of (poly)phenols in children and adults: cross-sectional analysis of UK National Diet and Nutrition Survey Rolling Programme (2008-2014)

PURPOSE

Current evidence accounts for the role of (poly)phenolic compounds in the prevention of non-communicable diseases. Detailed information on population-level intakes is required to translate these findings into recommendations. This work aimed to estimate (poly)phenol intake in the UK population using data from a nationally representative survey.

METHODS

Data from 9374 participants (4636 children aged 1.5-18 years and 4738 adults aged 19 years and over) from the National Diet and Nutrition Survey Rolling Programme (NDNS RP) 2008-2014 was used. (Poly)phenol content of foods consumed in the NDNS RP was identified using Phenol-Explorer and through literature searches. Data on flavonoids, phenolic acids, and stilbenes were collected. Total (poly)phenol content was also assessed.

RESULTS

Mean total (poly)phenol intake ranged from 266.6 ± 166.1 mg/day in children aged 1.5-3 years to 1035.1 ± 544.3 mg/day in adults aged 65 years and over, with flavan-3-ols and hydroxycinnamic acids being the most consumed (poly)phenols across all age groups. (Poly)phenol intake was higher in males in all age groups except for adults aged 19-34 and 50-64 years, where intakes were marginally higher in females. Energy-adjusted intakes accounted for the pattern of increasing (poly)phenol intakes with age and a higher intake was observed in females across all age groups, with the exception of children aged 1.5-3 years. The main food sources were non-alcoholic beverages and fruits, being the main compounds flavan-3-ols and caffeoylquinic acids.

CONCLUSIONS

This analysis provides estimates of (poly)phenol intake from a representative sample of the UK general population, which can help inform the health implications of (poly)phenol intake.

Evaluation of polyphenolic compounds in membrane concentrated pistachio hull extract

Pistachio hull is a substantial source of natural polyphenols, but a substantial volume is being wasted annually. Aqueous pistachio green hull extract (PGHE) was subjected to two-stage membrane process in order to separate a polyphenol rich fraction. The membrane conditions of each stage were investigated. Total phenolic content and antioxidant activity were determined by Folin-Ciocalteu and DPPH^· assay; also membrane fouling was monitored. The use of the 1 kDa cellulose membrane accompanied by 4 bar pressure and 250 rpm stirring speed was observed to be successful in the separation of a fraction with the highest amount of phenolic compound and antioxidant activity, in the retentate part. UHPLC/MSⁿ characterization of PGHE polyphenols enabled us to identify 34 compounds, including the most abundant galloylshikimic acids, gallic acid, theogallin, galloyl-O-hexoside, quercetin-O-hexoside and pyrogallol.

Consumption of orange fermented beverage improves antioxidant status and reduces peroxidation lipid and inflammatory markers in healthy humans

BACKGROUND

Alcoholic fermentation of fruits has generated novel products with high concentrations of bioactive compounds and moderate alcohol content. The aim of this study was to evaluate the potential effect on cardiovascular risk factors of the regular consumption by healthy humans of a beverage obtained by alcoholic fermentation and pasteurization of orange juice.

RESULTS

Thirty healthy volunteers were enrolled in a randomized controlled study. The experimental group (n = 15) drank 500 mL orange beverage (OB) per day for 2 weeks (intervention phase), followed by a 3-week washout phase. Blood samples were collected at baseline (E-T0) and at the end of the intervention (E-T1) and washout (E-T2) phases. Controls (n = 15) did not consume OB during a 2-week period. OB intake significantly increased oxygen radical absorbance capacity (43.9%) and reduced uric acid (-8.9%), catalase (CAT) (-23.2%), thiobarbituric acid reactive substances (TBARS) (-30.2%) and C-reactive protein (-2.1%) (E-T1 vs. E-T0). These effects may represent longer-term benefits, given the decreased uric acid (-8.9%), CAT (-34.6%), TBARS (-48.4%) and oxidized low-density lipoprotein (-23.9%) values recorded after the washout phase (E-T2 vs. E-T0).

CONCLUSION

The regular consumption of OB improved antioxidant status and decreased inflammation state, lipid peroxidation and uric acid levels. Thus OB may protect the cardiovascular system in healthy humans and be considered a novel functional beverage. © 2017 Society of Chemical Industry.

Claimed effects, outcome variables and methods of measurement for health claims proposed under European Community Regulation 1924/2006 in the area of blood glucose and insulin concentrations

Most requests for authorization to bear health claims under Articles 13(5) and 14 related to blood glucose and insulin concentration/regulation presented to the European Food Safety Authority (EFSA) receive a negative opinion. Reasons for such decisions are mainly ascribable to poor substantiation of the claimed effects. In this scenario, a project was carried out aiming at critically analysing the outcome variables (OVs) and methods of measurement (MMs) to be used to substantiate health claims, with the final purpose to improve the quality of applications provided by stakeholders to EFSA. This manuscript provides a position statement of the experts involved in the project, reporting the results of an investigation aimed to collect, collate and critically analyse the information relevant to claimed effects (CEs), OVs and MMs related to blood glucose and insulin levels and homoeostasis compliant with Regulation 1924/2006. The critical analysis of OVs and MMs was performed with the aid of the pertinent scientific literature and was aimed at defining their appropriateness (alone or in combination with others) to support a specific CE. The results can be used to properly select OVs and MMs in a randomized controlled trial, for an effective substantiation of the claims, using the reference method(s) whenever available. Moreover, results can help EFSA in updating the guidance for the scientific requirements of health claims.

Possible role of diet in cancer: systematic review and multiple meta-analyses of dietary patterns, lifestyle factors, and cancer risk

Context

Evidence of an association between dietary patterns derived a posteriori and risk of cancer has not been reviewed comprehensively.

Objective

The aim of this review was to investigate the relation between a posteriori-derived dietary patterns, grouped as healthy or unhealthy, and cancer risk. The relation between cancer risk and background characteristics associated with adherence to dietary patterns was also examined.

Data Sources

PubMed and Embase electronic databases were searched.

Study Selection

A total of 93 studies including over 85 000 cases, 100 000 controls, and 2 000 000 exposed individuals were selected.

Data Extraction

Data were extracted from each identified study using a standardized form by two independent authors.

Results

The most convincing evidence (significant results from prospective cohort studies) supported an association between healthy dietary patterns and decreased risk of colon and breast cancer, especially in postmenopausal, hormone receptor-negative women, and an association between unhealthy dietary patterns and increased risk of colon cancer. Limited evidence of a relation between an unhealthy dietary pattern and risk of upper aerodigestive tract, pancreatic, ovarian, endometrial, and prostatic cancers relied only on case-control studies. Unhealthy dietary patterns were associated with higher body mass index and energy intake, while healthy patterns were associated with higher education, physical activity, and less smoking. Potential differences across geographical regions require further evaluation.

Conclusions

The results suggest a potential role of diet in certain cancers, but the evidence is not conclusive and may be driven or mediated by lifestyle factors.