Effects of coffee consumption on glucose metabolism: A systematic review of clinical trials

Abstract

Epidemiological studies indicate an inverse association of coffee consumption with risk of type 2 diabetes mellitus. However, studies to determine the clinical effects of coffee consumption on the glucose metabolism biomarkers remain uncertain. The aim of this systematic review was to evaluate the effects of coffee consumption on glucose metabolism. A search of electronic databases ( PubMed and Web of Science) was performed identifying studies published until September 2017. Eight clinical trials (n = 247 subjects) were identified for analyses. Participants and studies characteristics, main findings, and study quality (Jadad Score) were reported. Short-term (1–3 h) and long-term (2–16 weeks) studies were summarized separately. Short-term studies showed that consumption of caffeinated coffee may increase the area under the curve for glucose response, while for long-term studies, caffeinated coffee may improve the glycaemic metabolism by reducing the glucose curve and increasing the insulin response. The findings suggest that consumption of caffeinated coffee may lead to unfavourable acute effects; however, an improvement on glucose metabolism was found on long-term follow-up.

Endocrine Effects of Coffee Consumption

“…So it was claimed that the positive effects on glucose metabolism may be due to chlorogenic acid and trigonelline, present in coffee (22). Studies involving animal models postulated that the reduction of blood glucose concentration by chlorogenic acid was mediated by the activation of adenosine monophosphate-activated protein kinase (AMPK), affecting fat and glucose metabolism at the cellular level (1,23). Evaluation of the effect of chronic consumption of caf-feine by animals was found to restore insulin sensitivity and revert age-induced insulin resistance in the rat.…”

“…Evaluation of the effect of chronic consumption of caf-feine by animals was found to restore insulin sensitivity and revert age-induced insulin resistance in the rat. The effect on Glut 4 transporters present in the skeletal muscles and AMPK activity along with the anti-oxidant and anti-inflammatory effects of coffee were hypothesized to contribute to glucose metabolism (1). The results of observational and clinical studies about the effects of coffee on glucose metabolism are contrary.…”

“…Studies suggested that 3-4 cups of coffee per day were capable of reducing the risk of development of T2DM (Type 2 Diabetes Mellitus) by approximately 25%, as compared to those consuming less than 2 cups per day. The relative risk of T2DM for the highest level of coffee intake (>6 cups/day) was estimated to be 0.71 (0.67-0.76) for caffeinated coffee and 0.79 (0.69-0.91) in case of decaffeinated coffee (1,4). In addition, increasing coffee consumption +1 cup/day incurred a decrease of 11% on T2DM risk in the following four years.…”

“…In addition, increasing coffee consumption +1 cup/day incurred a decrease of 11% on T2DM risk in the following four years. On the other hand, reducing coffee consumption by more than 1 cup/day increased the risk of development of T2DM in four years by 17% (1,5). Both caffeinated and decaffeinated coffee, filtered and instant coffee were associated with reduced risk of T2DM (6)(7)(8).…”

“…Coffee is one of the most popular beverages consumed worldwide, thereby enhancing its market demand (1). Statistics reveal that the average consumption of coffee ranges from 2-4 cups per day in western societies.…”