Coffee is one of the most widely consumed drinks worldwide.¹ Caffeine is a major component of coffee and has been a subject of attention in understanding its effect on human metabolism and specifically its effect on diabetes.

How Does Coffee Consumption Affect Diabetes Risk?

Numerous studies to date have found that coffee consumption is inversely related to the risk of developing type 2 diabetes mellitus (T2DM).^1,2 A 2005 systematic review of nine cohort studies found that higher coffee consumption was associated with lower risk of T2DM, with individuals who drank 4-6 cups of coffee/day and more than 6-7 cups of coffee/day experiencing 28% and 35% lowered T2DM risk, respectively, when compared to individuals who drank less than 2 cups of coffee/day.¹ A more recent systematic review and meta-analysis of 30 prospective studies found similar results, showing that habitual consumption of coffee was associated with a 30% decrease in T2DM risk and suggested that each cup of coffee was linked to a 6% risk reduction.² The latter systematic review also found no differences between caffeinated and decaffeinated coffee.

How Does Coffee Consumption Affect Blood Sugar Levels?

Mechanisms behind how coffee consumption affects T2DM risk are not yet fully understood.² However, studies suggest that acute coffee consumption reduces insulin sensitivity and glucose tolerance but that coffee consumption improves glucose metabolism and insulin response in the long term.³ Some hypothesize that coffee may increase energy expenditure by stimulating thermogenesis or that coffee increases satiety, leading to small reductions in caloric intake and allowing minor weight loss in the long-term. In addition, coffee contains various antioxidants and anti-inflammatory properties which may potentially ameliorate pathways associated with insulin resistance development.

Beware of Sugar-Sweetened Coffee

Although evidence strongly suggests that coffee consumption can be beneficial for decreasing the risk of developing diabetes, various studies report that habitual consumption of sugar-sweetened beverages have negative effects on metabolic health and the risk of developing diabetes.^4–6 Research shows that sugary beverages rapidly increase blood glucose levels, and sugar-sweetened coffee is not an exception. One of the reasons why coffee consumption may be beneficial to diabetes risk is that it may lower the consumption of soft drinks and other sugary beverages.² However, individuals should beware of consuming sweetened coffee or other caffeinated drinks in an effort to reduce risk of diabetes, as studies show that sugary coffee can raise blood glucose and hemoglobin A1c levels as well as the risk of diabetes.^5,6