Methyl Donor Nutrient Intake and Incidence of Type 2 Diabetes: Results From Three Large U.S. Cohorts.

OBJECTIVE: We examined whether intake of methyl donor nutrients, including vitamins B2, B6, and B12 and folate, from foods and/or supplements is associated with type 2 diabetes risk. RESEARCH DESIGN AND METHODS: We included 203,644 women and men from the Nurses' Health Study (1984-2016), Nurses' Health Study 2 (1991-2017), and Health Professionals Follow-Up Study (1986-2016). Dietary data were collected every 2-4 years with use of semiquantitative food-frequency questionnaires. Cox proportional hazards models with time-varying covariates were used to evaluate associations between each nutrient and type 2 diabetes risk. We combined cohort-specific hazard ratios (HRs) using inverse variance-weighted fixed-effects meta-analyses. RESULTS: During 4,900,181 person-years of follow-up, we documented 19,475 incident type 2 diabetes cases. In multivariable-adjusted meta-analyses, participants in the highest quintiles of total vitamin B2 and B6 intakes had lower risk of diabetes compared with those in the lowest quintiles (HR 0.93 [95% CI 0.89, 0.98] for B2 and 0.93 [0.89, 0.97] for B6). With stratification by source, significant associations remained for B2 from food but not from supplements. Neither association for B6 from food nor association for B6 from supplements attained significance. No association was observed between total B12 intake and diabetes. However, B12 from food was marginally associated with higher diabetes risk (1.05 [1.00-1.11]) but not after additional adjustment for red meat intake (1.04 [0.99-1.10]). No evidence of association was observed between intakes of folate and diabetes. CONCLUSIONS: The results of our study suggest that higher intake of vitamin B2 and B6, especially B2 from food sources, may be associated with a modestly lower type 2 diabetes risk.

Impact of Blueberry Consumption on the Human Fecal Bileacidome: A Pilot Study of Bile Acid Modulation by Freeze-Dried Blueberry.

Cholesterol-derived bile acids (BAs) affect numerous physiological functions such as glucose homeostasis, lipid metabolism and absorption, intestinal inflammation and immunity, as well as intestinal microbiota diversity. Diet influences the composition of the BA pool. In the present study, we analyzed the impact of a dietary supplementation with a freeze-dried blueberry powder (BBP) on the fecal BA pool composition. The diet of 11 men and 13 women at risk of metabolic syndrome was supplemented with 50 g/day of BBP for 8 weeks, and feces were harvested before (pre) and after (post) BBP consumption. BAs were profiled using liquid chromatography coupled with tandem mass spectrometry. No significant changes in total BAs were detected when comparing pre- vs. post-BBP consumption samples. However, post-BBP consumption samples exhibited significant accumulations of glycine-conjugated BAs (p = 0.04), glycochenodeoxycholic (p = 0.01), and glycoursodeoxycholic (p = 0.01) acids, as well as a significant reduction (p = 0.03) in the secondary BA levels compared with pre-BBP feces. In conclusion, the fecal bileacidome is significantly altered after the consumption of BBP for 8 weeks. While additional studies are needed to fully understand the underlying mechanisms and physiological implications of these changes, our data suggest that the consumption of blueberries can modulate toxic BA elimination.

Impact of Diet on Plasma Lipids in Individuals with Heterozygous Familial Hypercholesterolemia: A Systematic Review of Randomized Controlled Nutritional Studies.

BACKGROUND: Conclusive data on the effectiveness of dietary interventions in heterozygous familial hypercholesterolemia (HeFH) management are unavailable. Whether this is due to a true lack of effects or biases in intervention designs remains unsettled. We systematically assessed the impact on LDL-C of published dietary randomized controlled trials (RCTs) conducted among individuals with HeFH in relation to their design and risk of bias. METHODS: We systematically searched PubMed, Web of Science, and Embase in November 2020 to identify RCTs that assessed the impact of: (1) food-based interventions; (2) dietary counseling interventions; or (3) dietary supplements on LDL-C in individuals with HeFH. We evaluated the risk of bias of each study using the Cochrane Risk of Bias 2 method. RESULTS: A total of 19 RCTs comprising 837 individuals with HeFH were included. Of those, five were food-based interventions, three were dietary counseling interventions and 12 were dietary supplement-based interventions (omega-3, n = 3; phytosterols, n = 7; guar gum, n = 1; policosanol, n = 1). One study qualified both as a food-based intervention and as a dietary supplement intervention due to its factorial design. A significant reduction in LDL-C levels was reported in 10 RCTs, including eight dietary supplement interventions (phytosterols, n = 6, omega-3, n = 1; guar gum, n = 1), one food-based intervention and one dietary counseling intervention. A total of 13 studies were judged to have some methodological biases in a way that substantially lowers confidence in the results. Studies at low risk of biases were more likely to report significant reductions in LDL-C concentrations, compared with studies at risk of bias (chi-square statistic: 5.49; p = 0.02). CONCLUSION: This systemic review shows that the apparent lack of effectiveness of diet manipulation in modulating plasma levels of LDL-C among individuals with HeFH is likely due to biases in study designs, rather than a true lack of effects. The likelihood of reporting significant reductions in LDL-C was associated with the concurrent risk of bias.