Strong epidemiological evidence suggests that coffee consumption is associated with lower risk of type 2 diabetes. In postprandial studies, however, caffeine consumption has been associated with impaired glucose regulation.
To study the acute effects of coffee and caffeine-containing soft drinks on glycaemic and insulinaemic responses.
Twelve healthy volunteers were served each test food once and the reference glucose solution twice, containing 50 g of available carbohydrates, after an overnight fast at 1-week intervals in a random order. Capillary blood samples were drawn at 15-30 min intervals for 2 h after each study meal. The incremental areas under the curve (IAUC), glycaemic index (GI) and insulinaemic index (II), were calculated to estimate the glycaemic and insulinaemic responses.
Glucose and insulin responses of coffees with glucose containing 150 or 300 mg of caffeine did not differ from responses of pure glucose solution; the GIs were 104 and 103, and the IIs were 89 and 92, respectively. When a bun or sucrose and milk were consumed together with coffee, lower GI values and insulin responses were observed, reflecting the carbohydrate quality and protein content of the accompaniments. Sucrose-sweetened cola produced a high GI value of 90 and an II of 61.
Coffee does not modify glycaemic and insulinaemic responses when ingested with a carbohydrate source. Therefore, there is no need to avoid coffee as a choice of beverage in GI testing.