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Title: Dietary intakes of flavan-3-ols and cardiometabolic health: systematic review and meta-analysis of randomized trials and prospective cohort studies

Author
item RAMAN, GOWRI - Tufts University
item AVENDANO, ESTHER - Tufts University
item CHEN, SIYU - Tufts University
item WANG, JIAQI - Tufts University
item MATSON, JULIA - Brandeis University
item GAYER, BRIDGET - Tufts University
item Novotny, Janet
item CASSIDY, AEDIN - University Of East Anglia

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2019
Publication Date: 8/26/2019
Citation: Raman, G., Avendano, E., Chen, S., Wang, J., Matson, J., Gayer, B., Novotny, J.A., Cassidy, A. 2019. Dietary intakes of flavan-3-ols and cardiometabolic health: systematic review and meta-analysis of randomized trials and prospective cohort studies. American Journal of Clinical Nutrition. 110:1067-1078. https://doi.org/10.1093/ajcn/nqz178.
DOI: https://doi.org/10.1093/ajcn/nqz178

Interpretive Summary: There is considerable interest in the impact of consumption of a class of compounds called flavan-3-ols on cardiovascular disease and diabetes, and hundreds of scientific studies have been conducted to develop understanding of the relationships. Flavan-3-ols are found in foods like tea, cocoa, and berries. To evaluate the totality of the evidence, we synthesized the data from the many studies using a method called systematic review. We searched all major available databases to find all applicable published scientific studies, then we double-screened the publication abstracts and full-text articles. Next, we extracted the data and results and synthesized the data for statistical analysis. Overall, the studies suggested that the highest vs. lowest habitual intakes of flavan-3-ol significantly decreased cardiovascular mortality, coronary heart disease incidence, and diabetes. Flavan-3-ol intervention also resulted in significant improvements blood vessel reactivity, blood pressure, cholesterol, and markers of diabetes. The totality of the available evidence supports a beneficial effect of flavan-3-ol intake on cardio-metabolic outcomes, but the doses needed for these effects was not clear. These results will be used by scientists.

Technical Abstract: Although available data suggest that some sources of dietary flavan-3-ols reduce cardio-metabolic risk, no review has systematically synthesized their contribution for cardio-metabolic health. The objective of this study was to examine if higher flavan-3-ol intake, irrespective of dietary source, reduces cardiovascular disease (CVD) risk. MEDLINE, Cochrane Central, and Commonwealth Agricultural Bureau abstracts were searched for prospective cohorts and randomized controlled trials (RCTs) from 1946-January 2018 for publications on flavan-3-ol intake and CVD risk. Random-effects models meta-analysis was used. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was employed to assess the strength of evidence. Thirteen prospective cohorts (16 publications) found highest vs. lowest habitual intakes of flavan-3-ol significantly decreased CVD mortality (n=3), CHD incidence (n=2), and type 2 diabetes (T2DM) (n=4) (16%, 19% and 9%, respectively). No association was found for stroke or hypertension. Of eligible 153 RCTs, flavan-3-ol intervention resulted in significant improvements in acute and chronic flow-mediated dilation (FMD) (1.14%; 95%CI: 0.65, 1.63%), systolic (SBP) (-1.53 mmHg; 95% CI -2.37, -0.70 mmHg) and diastolic blood pressure (DBP) (-0.96 mmHg; 95% CI -1.49, -0.44 mmHg), total, low-density-lipoprotein and high-density-lipoprotein cholesterol, triglycerides, hemoglobin A1c (HbA1c), and homeostatic model assessment (HOMA-IR) (-0.17; 95% CI -0.33, -0.01). All analyses, except HbA1c, were associated with moderate/high heterogeneity. When analyses were limited to good methodological quality studies, only SPB, DBP, HOMA-IR, and acute and chronic FMD remained significant. In GRADE evaluations, there was moderate evidence in cohort studies that flavan-3-ol intake reduces CVD mortality, CHD and T2DM incidence and in RCTs that intervention decreased SBP, DBP and HOMA-IR. Available evidence supports a beneficial effect of flavan-3-ol intake on cardio-metabolic outcomes.