Abstract
Background Drinking coffee is habitually widespread around the world. Moderate coffee consumption has a beneficial health effect on the human body. However, there are controversial effects of consuming coffee on blood glucose and insulin levels in diabetic patients, which remain to be fully elucidated. Purpose The aim of this review was to clarify the relationship between coffee consumption and developing type 2 diabetes mellitus (T2DM). Methods The common internet search engines were utilized to access the abstracts and full text of articles published in English in the last 20 years. Results The association between the frequent consumption of coffee and the risk of developing type 2 diabetes has been studied intensively through epidemiologic and intervention studies. In fact, coffee is a major source of chlorogenic acids (CGAs) in the human diet. The presence of CGAs and other phenolic compounds in coffee plays a role in inhibiting glucose absorption via interference with glucose transporters and increasing insulin sensitivity. However, short-term trials confirmed the detrimental effects of heavily drinking coffee due to the presence of caffeine. Caffeine has been found to impair glucose tolerance and decrease insulin sensitivity. Conclusion Several clinical trials have confirmed the relationship between the consumption of coffee and the development of T2DM. Moderate consumption of coffee has been suggested for its long-term benefits and positive health effects.