(Poly)phenols have anti-diabetic properties that are mediated through the regulation of the main biomarkers associated with type 2 diabetes mellitus (T2DM) (fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), insulin resistance (IR)), as well as the modulation of other metabolic, inflammatory and oxidative stress pathways. A wide range of human and pre-clinical studies supports these effects for different plant products containing mixed (poly)phenols (e.g., berries, cocoa, tea) and for some single compounds (e.g., resveratrol). We went through some of the latest human intervention trials and pre-clinical studies looking at (poly)phenols against T2DM to update the current evidence and to examine the progress in this field to achieve consistent proof of the anti-diabetic benefits of these compounds. Overall, the reported effects remain small and highly variable, and the accumulated data are still limited and contradictory, as shown by recent meta-analyses. We found newly published studies with better experimental strategies, but there were also examples of studies that still need to be improved. Herein, we highlight some of the main aspects that still need to be considered in future studies and reinforce the messages that need to be taken on board to achieve consistent evidence of the anti-diabetic effects of (poly)phenols.
AIMS: To examine the association of alcohol consumption patterns with growth differentiation factor 15 (GDF-15) in older drinkers, separately among individuals with cardiovascular disease (CVD)/diabetes and those without them, as GDF-15 is a strong biomarker of chronic disease burden.
DESIGN: Cross-sectional study. SETTING: Population-based study in Madrid (Spain). PARTICIPANTS: A total of 2051 life-time drinkers aged 65+ years included in the Seniors-ENRICA-2 study in 2015-17. Participants' mean age was 71.4 years and 55.4% were men.
MEASUREMENTS: According to their average life-time alcohol intake, participants were classified as occasional ( 1.43-20 g/day; women: > 1.43-10 g/day), moderate-risk (men: > 20-40 g/day; women: > 10-20 g/day) and high-risk drinkers (men: > 40 g/day; women: > 20 g/day; or binge drinkers). We also ascertained wine preference (> 80% of alcohol derived from wine), drinking with meals and adherence to a Mediterranean drinking pattern (MDP) defined as low-risk drinking, wine preference and one of the following: drinking only with meals; higher adherence to the Mediterranean diet; or any of these.
FINDINGS: In participants without CVD/diabetes, GDF-15 increased by 0.27% [95% confidence interval (CI) = 0.06%, 0.48%] per 1 g/day increment in alcohol among high-risk drinkers, but there was no clear evidence of association in those with lower intakes or in the overall group, or across categories of alcohol consumption status. Conversely, among those with CVD/diabetes, GDF-15 rose by 0.19% (95% CI = 0.05%, 0.33%) per 1 g/day increment in the overall group and GDF-15 was 26.89% (95% CI = 12.93%, 42.58%) higher in high-risk versus low-risk drinkers. Drinking with meals did not appear to be related to GDF-15, but among those without CVD/diabetes, wine preference and adherence to the MDP were associated with lower GDF-15, especially when combined with high adherence to the Mediterranean diet.
CONCLUSIONS: Among older life-time drinkers in Madrid, Spain, high-risk drinking was positively associated with growth differentiation factor 15 (a biomarker of chronic disease burden). There was inconclusive evidence of a beneficial association for low-risk consumption.
AIMS: Randomized controlled trials have demonstrated the efficacy of several dietary patterns plus physical activity to reduce diabetes onset in people with prediabetes. However, there is no evidence on the effect from the Mediterranean diet on the progression from prediabetes to diabetes. We aimed to evaluate the effect from high adherence to Mediterranean diet on the risk of diabetes in individuals with prediabetes.
METHODS: Prospective cohort study in Spanish Primary Care setting. A total of 1184 participants with prediabetes based on levels of fasting plasma glucose and/or glycated hemoglobin were followed up for a mean of 4.2 years. A total of 210 participants developed diabetes type 2 during the follow up. Hazard ratios of diabetes onset were estimated by Cox proportional regression models associated to high versus low/medium adherence to Mediterranean diet. Different propensity score methods were used to control for potential confounders.
RESULTS: Incidence rate of diabetes in participants with high versus low/medium adherence to Mediterranean diet was 2.9 versus 4.8 per 100 persons-years. The hazard ratios adjusted for propensity score and by inverse probability weighting (IPW) had identical magnitude: 0.63 (95% confidence interval, 0.43-0.93). The hazard ratio in the adjusted model using propensity score matching 1:2 was 0.56 (95% confidence interval, 0.37-0.84).
CONCLUSIONS: These propensity score analyses suggest that high adherence to Mediterranean diet reduces diabetes risk in people with prediabetes.
PURPOSE: Previous meta-analyses assessed the association of adherence to the Mediterranean dietary pattern (MedDiet) with the risk of type 2 diabetes (T2D). Since then, new large-scale cohort studies have been published. In addition, dose-response relation was not previously investigated and the certainty of evidence was not assessed. We aimed to explore the dose-response relationship between adherence to the MedDiet and the risk of T2D.
METHODS: We did a systematic search using PubMed, Scopus, and ISI Web of Science up to April 2021 for prospective cohort studies of the relationship between adherence to the MedDiet and the risk of T2D in the general population. The summary relative risks (RR) and 95%CI were estimated by applying a random-effects model.
RESULTS: Fourteen prospective cohort studies (410,303 participants and 41,466 cases) were included. There was an inverse association for the highest versus lowest category of adherence to the MedDiet (RR: 0.79, 95%CI 0.72, 0.88; I(2) = 82%, n = 14; Risk difference: - 21 per 1000 person, 95%CI - 28, - 12; GRADE = moderate certainty), and for a 2-point increment in the MedDiet adherence score (RR: 0.86, 95%CI 0.82, 0.91; n = 13). The RR remained significant after controlling for important confounders and in almost all subgroups, especially subgroups defined by geographical region. We observed an inverse linear association between MedDiet adherence score and T2D incidence.
CONCLUSION: Adherence to the MedDiet was inversely related to T2D risk in a dose-response manner. Adherence to a Mediterranean-style diet may be a good advice for the primary prevention of T2D.
REGISTRY AND REGISTRY NUMBER: PROSPERO (CRD42021246589).