Dietary protein intake in midlife in relation to healthy aging - results from the prospective Nurses' Health Study cohort.

BACKGROUND: Protein intake plays an important role in maintaining the health status of older adults. However, few epidemiologic studies examined midlife protein intake in relation to healthy aging. OBJECTIVES: The objective of this study was to evaluate the long-term role of dietary protein intake in healthy aging among female participants in the prospective Nurses' Health Study (NHS) cohort. METHODS: We included 48,762 NHS participants aged <60 y in 1984. Total protein, animal protein, dairy protein (a subset of animal protein), and plant protein were derived from validated food frequency questionnaires. Healthy aging was defined as being free from 11 major chronic diseases, having good mental health, and not having impairments in either cognitive or physical function, as assessed in the 2014 or 2016 NHS participant questionnaires. We used multivariate logistic regression adjusted for lifestyle, demographics, and health status to estimate the odds ratios (ORs) and 95% confidence intervals for protein intake in relation to healthy aging. RESULTS: A total of 3721 (7.6%) NHS participants met our healthy aging definition. Protein intake was significantly associated with higher odds of healthy aging. The ORs (95% confidence intervals) per 3%-energy increment with healthy aging were 1.05 (1.01, 1.10) for total protein, 1.07 (1.02, 1.11) for animal protein, 1.14 (1.06, 1.23) for dairy protein, and 1.38 (1.24, 1.54) for plant protein. Plant protein was also associated with higher odds of absence of physical function limitations and good mental status. In substitution analyses, we observed significant positive associations for the isocaloric replacement of animal or dairy protein, carbohydrate, or fat with plant protein (ORs for healthy aging: 1.22-1.58 for 3% energy replacement with plant protein). CONCLUSIONS: Dietary protein intake, especially plant protein, in midlife, is associated with higher odds of healthy aging and with several domains of positive health status in a large cohort of female nurses.

Omega-3 Blood Levels and Stroke Risk: A Pooled and Harmonized Analysis of 183 291 Participants From 29 Prospective Studies.

BACKGROUND: The effect of marine omega-3 PUFAs on risk of stroke remains unclear. METHODS: We investigated the associations between circulating and tissue omega-3 PUFA levels and incident stroke (total, ischemic, and hemorrhagic) in 29 international prospective cohorts. Each site conducted a de novo individual-level analysis using a prespecified analytical protocol with defined exposures, covariates, analytical methods, and outcomes; the harmonized data from the studies were then centrally pooled. Multivariable-adjusted HRs and 95% CIs across omega-3 PUFA quintiles were computed for each stroke outcome. RESULTS: Among 183 291 study participants, there were 10 561 total strokes, 8220 ischemic strokes, and 1142 hemorrhagic strokes recorded over a median of 14.3 years follow-up. For eicosapentaenoic acid, comparing quintile 5 (Q5, highest) with quintile 1 (Q1, lowest), total stroke incidence was 17% lower (HR, 0.83 [CI, 0.76-0.91]; P<0.0001), and ischemic stroke was 18% lower (HR, 0.82 [CI, 0.74-0.91]; P<0.0001). For docosahexaenoic acid, comparing Q5 with Q1, there was a 12% lower incidence of total stroke (HR, 0.88 [CI, 0.81-0.96]; P=0.0001) and a 14% lower incidence of ischemic stroke (HR, 0.86 [CI, 0.78-0.95]; P=0.0001). Neither eicosapentaenoic acid nor docosahexaenoic acid was associated with a risk for hemorrhagic stroke. These associations were not modified by either baseline history of AF or prevalent CVD. CONCLUSIONS: Higher omega-3 PUFA levels are associated with lower risks of total and ischemic stroke but have no association with hemorrhagic stroke.

Omega-3 Fatty Acid Biomarkers and Incident Atrial Fibrillation.

BACKGROUND: The relationship between omega-3 fatty acids and atrial fibrillation (AF) remains controversial. OBJECTIVES: This study aimed to determine the prospective associations of blood or adipose tissue levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) with incident AF. METHODS: We used participant-level data from a global consortium of 17 prospective cohort studies, each with baseline data on blood or adipose tissue omega-3 fatty acid levels and AF outcomes. Each participating study conducted a de novo analyses using a prespecified analytical plan with harmonized definitions for exposures, outcome, covariates, and subgroups. Associations were pooled using inverse-variance weighted meta-analysis. RESULTS: Among 54,799 participants from 17 cohorts, 7,720 incident cases of AF were ascertained after a median 13.3 years of follow-up. In multivariable analysis, EPA levels were not associated with incident AF, HR per interquintile range (ie, the difference between the 90th and 10th percentiles) was 1.00 (95% CI: 0.95-1.05). HRs for higher levels of DPA, DHA, and EPA+DHA, were 0.89 (95% CI: 0.83-0.95), 0.90 (95% CI: 0.85-0.96), and 0.93 (95% CI: 0.87-0.99), respectively. CONCLUSIONS: In vivo levels of omega-3 fatty acids including EPA, DPA, DHA, and EPA+DHA were not associated with increased risk of incident AF. Our data suggest the safety of habitual dietary intakes of omega-3 fatty acids with respect to AF risk. Coupled with the known benefits of these fatty acids in the prevention of adverse coronary events, our study suggests that current dietary guidelines recommending fish/omega-3 fatty acid consumption can be maintained.

A prospective analysis of red blood cell membrane polyunsaturated fatty acid levels and risk of non-Hodgkin lymphoma.

Published studies report inconsistent associations of polyunsaturated fatty acid (PUFA) intake with non-Hodgkin lymphoma (NHL) risk. We conducted a nested case-control study in Nurses' Health Study and Health Professionals Follow-Up Study participants to evaluate a hypothesis of inverse association of pre-diagnosis red blood cell (RBC) membrane PUFA levels with risk of NHL endpoints. We confirmed 583 NHL cases and matched 583 controls by cohort/sex, age, race and blood draw date/time. We estimated odds ratios (OR) and 95% confidence intervals (CI) for risk of NHL endpoints using logistic regression. RBC PUFA levels were not associated with all NHL risk; cis 20:2n-6 was associated with follicular lymphoma risk (OR [95% CI] per one standard deviation increase: 1.35 [1.03-1.77]), and the omega-6/omega-3 PUFA ratio was associated with diffuse large B-cell lymphoma risk (2.33 [1.23-4.43]). Overall, PUFA did not demonstrate a role in NHL etiology; the two unexpected positive associations lack clear biologic explanations.

Intake of fruits and vegetables by pesticide residue status in relation to cancer risk.

BACKGROUND: Conventionally grown fruits and vegetables (FVs) are the main source of general population exposure to pesticide residues. OBJECTIVE: To evaluate the relation of intake of high- and low-pesticide-residue FVs with cancer risk. METHODS: We followed 150,830 women (Nurses' Health Study, 1998-2016, and Nurses' Health Study II, 1999-2017) and 29,486 men (Health Professionals Follow-up Study, 1998-2016) without a history of cancer. We ascertained FV intake via validated food frequency questionnaires and categorized FVs as having high or low pesticide residue levels based on USDA surveillance data. We used Cox proportional hazards models to estimate hazard ratios (HR) and 95% confidence intervals (CI) of total and site-specific cancer related to quintiles of high- and low-pesticide-residue FV intake. RESULTS: We documented 23,678 incident cancer cases during 2,862,118 person-years of follow-up. In the pooled multivariable analysis, neither high- nor low-pesticide-residue FV intake was associated with cancer. The HRs (95% CI) per 1 serving/day increase in intake were 0.99 (0.97-1.01) for high- and 1.01 (0.99-1.02) for low-pesticide-residue FVs. Additionally, we found no association between high-pesticide-residue FV intake and risk of specific sites, including malignancies previously linked to occupational pesticide exposure ([HR, 95% CI comparing extreme quintiles of intake] lung [1.17 (0.95-1.43)], non-Hodgkin lymphoma [0.89 (0.72-1.09)], prostate [1.31 (0.88-1.93)]) or inversely related to intake of organic foods (breasts [1.03 (0.94-1.31)]). CONCLUSIONS: These findings suggest that overall exposure to pesticides through FV intake is not related to cancer risk, although they do not rule out associations with specific chemicals or sub-types of specific cancers.

n-3 Fatty Acid Biomarkers and Incident Type 2 Diabetes: An Individual Participant-Level Pooling Project of 20 Prospective Cohort Studies.

OBJECTIVE: Prospective associations between n-3 fatty acid biomarkers and type 2 diabetes (T2D) risk are not consistent in individual studies. We aimed to summarize the prospective associations of biomarkers of α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) with T2D risk through an individual participant-level pooled analysis. RESEARCH DESIGN AND METHODS: For our analysis we incorporated data from a global consortium of 20 prospective studies from 14 countries. We included 65,147 participants who had blood measurements of ALA, EPA, DPA, or DHA and were free of diabetes at baseline. De novo harmonized analyses were performed in each cohort following a prespecified protocol, and cohort-specific associations were pooled using inverse variance-weighted meta-analysis. RESULTS: A total of 16,693 incident T2D cases were identified during follow-up (median follow-up ranging from 2.5 to 21.2 years). In pooled multivariable analysis, per interquintile range (difference between the 90th and 10th percentiles for each fatty acid), EPA, DPA, DHA, and their sum were associated with lower T2D incidence, with hazard ratios (HRs) and 95% CIs of 0.92 (0.87, 0.96), 0.79 (0.73, 0.85), 0.82 (0.76, 0.89), and 0.81 (0.75, 0.88), respectively (all P < 0.001). ALA was not associated with T2D (HR 0.97 [95% CI 0.92, 1.02]) per interquintile range. Associations were robust across prespecified subgroups as well as in sensitivity analyses. CONCLUSIONS: Higher circulating biomarkers of seafood-derived n-3 fatty acids, including EPA, DPA, DHA, and their sum, were associated with lower risk of T2D in a global consortium of prospective studies. The biomarker of plant-derived ALA was not significantly associated with T2D risk.

Red blood cell membrane trans fatty acid levels and risk of non-Hodgkin lymphoma: a prospective nested case-control study.

BACKGROUND: Trans fatty acid (TFA) intake persists in much of the world, posing ongoing threats to public health that warrant further elucidation. Published evidence suggests a positive association of self-reported TFA intake with non-Hodgkin lymphoma (NHL) risk. OBJECTIVES: To confirm those reports, we conducted a prospective study of prediagnosis RBC membrane TFA levels and risk of NHL and common NHL histologic subtypes. METHODS: We conducted a nested case-control study in Nurses' Health Study and Health Professionals Follow-Up Study participants with archived RBC specimens and no history of cancer at blood draw (1989-1090 and 1994-1995, respectively). We confirmed 583 incident NHL cases (332 women and 251 men) and individually matched 583 controls on cohort (sex), age, race, and blood draw date/time. We analyzed RBC membrane TFA using GLC (in 2013-2014) and expressed individual TFA levels as a percentage of total fatty acids. We used unconditional logistic regression adjusted for the matching factors to estimate ORs and 95% CIs for overall NHL risk per 1 SD increase in TFA level and assessed histologic subtype-specific associations with multivariable polytomous logistic regression. RESULTS: Total and individual TFA levels were not associated with risk of all NHL or most subtypes. We observed a positive association of total TFA levels with diffuse large B cell lymphoma (DLBCL) risk [n = 98 cases; OR (95% CI) per 1 SD increase: 1.30 (1.05, 1.61); P = 0.015], driven by trans 18:1n-9(ω-9)/elaidic acid [OR (95% CI): 1.34 (1.08, 1.66); P = 0.007], trans 18:1n-7/vaccenic acid [OR (95% CI): 1.28 (1.04, 1.58); P = 0.023], and trans 18:2n-6t,t [OR (95% CI): 1.26 (1.01, 1.57); P = 0.037]. CONCLUSIONS: Our findings extended evidence for TFA intake and DLBCL risk but not for other NHL subtypes. Reduced TFA consumption through dietary choices or health policy measures may support prevention of DLBCL, an aggressive NHL subtype.

Fatty acids in the de novo lipogenesis pathway and incidence of type 2 diabetes: A pooled analysis of prospective cohort studies.

BACKGROUND: De novo lipogenesis (DNL) is the primary metabolic pathway synthesizing fatty acids from carbohydrates, protein, or alcohol. Our aim was to examine associations of in vivo levels of selected fatty acids (16:0, 16:1n7, 18:0, 18:1n9) in DNL with incidence of type 2 diabetes (T2D). METHODS AND FINDINGS: Seventeen cohorts from 12 countries (7 from Europe, 7 from the United States, 1 from Australia, 1 from Taiwan; baseline years = 1970-1973 to 2006-2010) conducted harmonized individual-level analyses of associations of DNL-related fatty acids with incident T2D. In total, we evaluated 65,225 participants (mean ages = 52.3-75.5 years; % women = 20.4%-62.3% in 12 cohorts recruiting both sexes) and 15,383 incident cases of T2D over the 9-year follow-up on average. Cohort-specific association of each of 16:0, 16:1n7, 18:0, and 18:1n9 with incident T2D was estimated, adjusted for demographic factors, socioeconomic characteristics, alcohol, smoking, physical activity, dyslipidemia, hypertension, menopausal status, and adiposity. Cohort-specific associations were meta-analyzed with an inverse-variance-weighted approach. Each of the 4 fatty acids positively related to incident T2D. Relative risks (RRs) per cohort-specific range between midpoints of the top and bottom quintiles of fatty acid concentrations were 1.53 (1.41-1.66; p < 0.001) for 16:0, 1.40 (1.33-1.48; p < 0.001) for 16:1n-7, 1.14 (1.05-1.22; p = 0.001) for 18:0, and 1.16 (1.07-1.25; p < 0.001) for 18:1n9. Heterogeneity was seen across cohorts (I2 = 51.1%-73.1% for each fatty acid) but not explained by lipid fractions and global geographical regions. Further adjusted for triglycerides (and 16:0 when appropriate) to evaluate associations independent of overall DNL, the associations remained significant for 16:0, 16:1n7, and 18:0 but were attenuated for 18:1n9 (RR = 1.03, 95% confidence interval (CI) = 0.94-1.13). These findings had limitations in potential reverse causation and residual confounding by imprecisely measured or unmeasured factors. CONCLUSIONS: Concentrations of fatty acids in the DNL were positively associated with T2D incidence. Our findings support further work to investigate a possible role of DNL and individual fatty acids in the development of T2D.

Circulating Very-Long-Chain SFA Concentrations Are Inversely Associated with Incident Type 2 Diabetes in US Men and Women.

BACKGROUND: Very-long-chain SFAs (VLCSFAs), such as arachidic acid (20:0), behenic acid (22:0), and lignoceric acid (24:0), have demonstrated inverse associations with cardiometabolic conditions, although more evidence is needed to characterize their relation with risk of type 2 diabetes (T2D). In addition, little is known regarding their potential dietary and lifestyle predictors. OBJECTIVE: We aimed to examine the association of plasma and erythrocyte concentrations of VLCSFAs with incident T2D risk. METHODS: We used existing measurements of fatty acid concentrations in plasma and erythrocytes among 2854 and 2831 participants in the Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS), respectively. VLCSFAs were measured using GLC, and individual fatty acid concentrations were expressed as a percentage of total fatty acids. Incident T2D cases were identified by self-reports and confirmed by a validated supplementary questionnaire. Cox proportional hazards regression was used to evaluate the association between VLCSFAs and T2D, adjusting for demographic, lifestyle, and dietary variables. RESULTS: During 39,941 person-years of follow-up, we documented 243 cases of T2D. Intakes of peanuts, peanut butter, vegetable fat, dairy fat, and palmitic/stearic (16:0-18:0) fatty acids were significantly, albeit weakly, correlated with plasma and erythrocyte VLCSFA concentrations (|rs| ≤ 0.19). Comparing the highest with the lowest quartiles of plasma concentrations, pooled HRs (95% CIs) were 0.51 (0.35, 0.75) for arachidic acid, 0.43 (0.28, 0.64) for behenic acid, 0.40 (0.27, 0.61) for lignoceric acid, and 0.41 (0.27, 0.61) for the sum of VLCSFAs, after multivariate adjustments for demographic, lifestyle, and dietary factors. For erythrocyte VLCSFAs, only arachidic acid and behenic acid concentrations were inversely associated with T2D risk. CONCLUSIONS: Our findings suggest that, in US men and women, higher plasma concentrations of VLCSFAs are associated with lower risk of T2D. More research is needed to understand the mechanistic pathways underlying these associations.

Dairy fat intake and risk of type 2 diabetes in 3 cohorts of US men and women.

BACKGROUND: Previous studies have examined dairy products with various fat contents in relation to type 2 diabetes (T2D) risk, although data regarding dairy fat intake per se are sparse. OBJECTIVES: We aimed to evaluate the association between dairy fat intake and risk of T2D in 3 prospective cohorts. We also examined associations for isocalorically replacing dairy fat with other macronutrients. METHODS: We prospectively followed 41,808 men in the Health Professionals Follow-Up Study (HPFS; 1986-2012), 65,929 women in the Nurses' Health Study (NHS; 1984-2012), and 89,565 women in the NHS II (1991-2013). Diet was assessed quadrennially using validated FFQs. Fat intake from dairy products and other relevant sources was expressed as percentage of total energy. Self-reported incident T2D cases were confirmed using validated supplementary questionnaires. Time-dependent Cox proportional hazards regression was used to estimate the HR for dairy fat intake and T2D risk. RESULTS: During 4,219,457 person-years of follow-up, we documented 16,511 incident T2D cases. Dairy fat was not associated with risk of T2D when compared with calories from carbohydrates (HR for extreme quintiles: 0.98; 95% CI: 0.95, 1.02). Replacing 5% of calories from dairy fat with other sources of animal fat or carbohydrate from refined grains was associated with a 17% (HR: 1.17; 95% CI: 1.13, 1.21) and a 4% (HR: 1.04; 95% CI: 1.00, 1.08) higher risk of T2D, respectively. Conversely, a 5% calorie replacement with carbohydrate from whole grains was associated with a 7% lower risk of T2D (HR: 0.93; 95% CI: 0.88, 0.98). CONCLUSIONS: Dairy fat intake was not associated with T2D risk in these cohort studies of US men and women when compared with calories from carbohydrate. Replacing dairy fat with carbohydrates from whole grains was associated with lower risk of T2D. Replacement with other animal fats or refined carbohydrates was associated with higher risk.

Fatty acid biomarkers of dairy fat consumption and incidence of type 2 diabetes: A pooled analysis of prospective cohort studies.

BACKGROUND: We aimed to investigate prospective associations of circulating or adipose tissue odd-chain fatty acids 15:0 and 17:0 and trans-palmitoleic acid, t16:1n-7, as potential biomarkers of dairy fat intake, with incident type 2 diabetes (T2D). METHODS AND FINDINGS: Sixteen prospective cohorts from 12 countries (7 from the United States, 7 from Europe, 1 from Australia, 1 from Taiwan) performed new harmonised individual-level analysis for the prospective associations according to a standardised plan. In total, 63,682 participants with a broad range of baseline ages and BMIs and 15,180 incident cases of T2D over the average of 9 years of follow-up were evaluated. Study-specific results were pooled using inverse-variance-weighted meta-analysis. Prespecified interactions by age, sex, BMI, and race/ethnicity were explored in each cohort and were meta-analysed. Potential heterogeneity by cohort-specific characteristics (regions, lipid compartments used for fatty acid assays) was assessed with metaregression. After adjustment for potential confounders, including measures of adiposity (BMI, waist circumference) and lipogenesis (levels of palmitate, triglycerides), higher levels of 15:0, 17:0, and t16:1n-7 were associated with lower incidence of T2D. In the most adjusted model, the hazard ratio (95% CI) for incident T2D per cohort-specific 10th to 90th percentile range of 15:0 was 0.80 (0.73-0.87); of 17:0, 0.65 (0.59-0.72); of t16:1n7, 0.82 (0.70-0.96); and of their sum, 0.71 (0.63-0.79). In exploratory analyses, similar associations for 15:0, 17:0, and the sum of all three fatty acids were present in both genders but stronger in women than in men (pinteraction < 0.001). Whereas studying associations with biomarkers has several advantages, as limitations, the biomarkers do not distinguish between different food sources of dairy fat (e.g., cheese, yogurt, milk), and residual confounding by unmeasured or imprecisely measured confounders may exist. CONCLUSIONS: In a large meta-analysis that pooled the findings from 16 prospective cohort studies, higher levels of 15:0, 17:0, and t16:1n-7 were associated with a lower risk of T2D.

Joint effects of fatty acid desaturase 1 polymorphisms and dietary polyunsaturated fatty acid intake on circulating fatty acid proportions.

Background: Polyunsaturated fatty acids (PUFAs) are associated with a lower risk of multiple diseases. Fatty acid desaturase 1 gene (FADS1) polymorphisms and dietary PUFA intake are both established determinants of circulating PUFA proportions. Objective: We explored the joint effects of FADS1 polymorphisms and dietary PUFA intake on circulating PUFA proportions. Design: We studied 2288 participants from a nested case-control study of coronary artery disease among participants who provided blood samples in the Nurses' Health Study and the Health Professionals Follow-Up Study. Dietary PUFA intake was obtained from semiquantitative food-frequency questionnaires. FADS1 rs174546 was genotyped by using the Affymetrix 6.0 platform, and circulating PUFA proportions were measured with gas-liquid chromatography. Linear regression models were used to examine the associations between rs174546 and circulating proportions of each fatty acid. Gene-diet interactions were tested by including a cross-product term of dietary intake of each PUFA by rs174546 genotype in the linear regression models. Results: After adjustment for sex and ancestry, each copy of the C allele of rs174546 was associated with higher circulating proportions of arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) and lower proportions of linoleic acid and α-linolenic acid. The magnitude of positive association between higher consumption of dietary EPA or DHA and circulating proportions of EPA increased with each copy of the rs174546_T allele (P-interaction = 0.01 and 0.007, respectively). Each 1-SD increment in EPA intake was associated with an average 3.7% increase in circulating EPA proportions among participants with the rs174546_CC genotype and an average 7.8% increase among participants with the TT genotype. Conclusions: Carriers of the T allele at FADS1 rs174546 may need higher doses of dietary EPA and DHA to achieve the same circulating proportions of EPA as carriers of the C allele. The implications of these findings on disease risk and dietary guidelines require further study.

Omega-6 fatty acid biomarkers and incident type 2 diabetes: pooled analysis of individual-level data for 39 740 adults from 20 prospective cohort studies.

BACKGROUND: The metabolic effects of omega-6 polyunsaturated fatty acids (PUFAs) remain contentious, and little evidence is available regarding their potential role in primary prevention of type 2 diabetes. We aimed to assess the associations of linoleic acid and arachidonic acid biomarkers with incident type 2 diabetes. METHODS: We did a pooled analysis of new, harmonised, individual-level analyses for the biomarkers linoleic acid and its metabolite arachidonic acid and incident type 2 diabetes. We analysed data from 20 prospective cohort studies from ten countries (Iceland, the Netherlands, the USA, Taiwan, the UK, Germany, Finland, Australia, Sweden, and France), with biomarkers sampled between 1970 and 2010. Participants included in the analyses were aged 18 years or older and had data available for linoleic acid and arachidonic acid biomarkers at baseline. We excluded participants with type 2 diabetes at baseline. The main outcome was the association between omega-6 PUFA biomarkers and incident type 2 diabetes. We assessed the relative risk of type 2 diabetes prospectively for each cohort and lipid compartment separately using a prespecified analytic plan for exposures, covariates, effect modifiers, and analysis, and the findings were then pooled using inverse-variance weighted meta-analysis. FINDINGS: Participants were 39 740 adults, aged (range of cohort means) 49-76 years with a BMI (range of cohort means) of 23·3-28·4 kg/m2, who did not have type 2 diabetes at baseline. During a follow-up of 366 073 person-years, we identified 4347 cases of incident type 2 diabetes. In multivariable-adjusted pooled analyses, higher proportions of linoleic acid biomarkers as percentages of total fatty acid were associated with a lower risk of type 2 diabetes overall (risk ratio [RR] per interquintile range 0·65, 95% CI 0·60-0·72, p<0·0001; I2=53·9%, pheterogeneity=0·002). The associations between linoleic acid biomarkers and type 2 diabetes were generally similar in different lipid compartments, including phospholipids, plasma, cholesterol esters, and adipose tissue. Levels of arachidonic acid biomarker were not significantly associated with type 2 diabetes risk overall (RR per interquintile range 0·96, 95% CI 0·88-1·05; p=0·38; I2=63·0%, pheterogeneity<0·0001). The associations between linoleic acid and arachidonic acid biomarkers and the risk of type 2 diabetes were not significantly modified by any prespecified potential sources of heterogeneity (ie, age, BMI, sex, race, aspirin use, omega-3 PUFA levels, or variants of the FADS gene; all pheterogeneity≥0·13). INTERPRETATION: Findings suggest that linoleic acid has long-term benefits for the prevention of type 2 diabetes and that arachidonic acid is not harmful. FUNDING: Funders are shown in the appendix.

Contribution of the Nurses' Health Studies to Uncovering Risk Factors for Type 2 Diabetes: Diet, Lifestyle, Biomarkers, and Genetics.

OBJECTIVES: To review the contribution of the Nurses' Health Study (NHS) and the NHS II to addressing hypotheses regarding risk factors for type 2 diabetes. METHODS: We carried out a narrative review of 1976 to 2016 NHS and NHS II publications. RESULTS: The NHS and NHS II have uncovered important roles in type 2 diabetes for individual nutrients, foods, dietary patterns, and physical activity independent of excess body weight. Up to 90% of type 2 diabetes cases are potentially preventable if individuals follow a healthy diet and lifestyle. The NHS investigations have also identified novel biomarkers for diabetes, including adipokines, inflammatory cytokines, nutrition metabolites, and environmental pollutants, offering new insights into the pathophysiology of the disease. Global collaborative efforts have uncovered many common genetic variants associated with type 2 diabetes and improved our understanding of gene-environment interactions. Continued efforts to identify epigenetic, metagenomic, and metabolomic risk factors for type 2 diabetes have the potential to reveal new pathways and improve prediction and prevention. CONCLUSIONS: Over the past several decades, the NHS and NHS II have made major contributions to public health recommendations and strategies designed to reduce the global burden of diabetes.

Diet, lifestyle, and genetic risk factors for type 2 diabetes: a review from the Nurses' Health Study, Nurses' Health Study 2, and Health Professionals' Follow-up Study.

The epidemiological evidence collected from three large US cohorts (Nurses' Health Study, Nurses' Health Study 2, and Health Professionals' Follow-up Study) has yielded important information regarding the roles of overall diet, individual foods and nutrients, physical activity and other lifestyle factors in the development of type 2 diabetes. Excess adiposity is a major risk factor for diabetes, and thus, maintaining a healthy body weight and avoidance of weight gain during adulthood is the cornerstone of diabetes prevention. Independent of body weight, the quality or type of dietary fat and carbohydrate is more crucial than the quantity in determining diabetes risk. Higher consumption of coffee, whole grains, fruits, and nuts is associated with lower risk of diabetes, whereas regular consumption of refined grains, red and processed meats, and sugar-sweetened beverages including fruits juices is associated with increased risk. Dietary patterns rich in fruits and vegetables, whole grains, and nuts and legumes but lower in red and processed meats, refined grains, and sugar-sweetened beverages are consistently associated with diabetes risk, even after adjustment for body mass index. The genome-wide association studies conducted in these cohorts have contributed substantially to the discoveries of novel genetic loci for type 2 diabetes and other metabolic traits, although the identified common variants explain only a small proportion of overall diabetes predisposition. Taken together, these ongoing large cohort studies have provided convincing epidemiologic evidence that a healthy diet, together with regular physical activity, maintenance of a healthy weight, moderate alcohol consumption, and avoidance of sedentary behaviors and smoking would prevent the majority of type 2 diabetes cases.