Protective effects of tea, red wine and cocoa in diabetes. Evidences from human studies

•The current state-of-the-art on diabetes and tea, red wine and cocoa consumption is reviewed.•Epidemiologic and interventional studies mostly support a benefit of tea, red wine and cocoa intake against diabetes.•New human studies should be encouraged to clarify the equivocal evidences before giving any recommendation to the population.•The mechanisms behind potential tea, red wine and cocoa benefits against diabetes should be further investigated.

Prevention of diabetes through the diet has recently received an increasing interest, and polyphenolic compounds, such as flavanols, have become important potential chemopreventive natural agents due to their proved benefits on health, with low toxicity and cost. Tea, red wine and cocoa are good sources of flavanols and these highly consumed foods might contribute to prevent diabetes. In this regard, there is increasing evidence for a protective effect of tea, red wine and cocoa consumption against this disorder. This review summarizes the available epidemiological and interventional human studies providing evidence for and against this effect. Overall observational data suggest a benefit, but results are still equivocal and likely confounded by lifestyle and background dietary factors. The weight of data indicate favourable effects on diabetes risk factors for tea, red wine and cocoa intake, and a number of plausible mechanisms have been elucidated in human studies. However, despite the growing evidence it remains uncertain whether tea, red wine and cocoa consumption should be recommended to the general population or to patients as a strategy to reduce the risk of diabetes.