HealthDay News — Daily coffee consumption is associated with a significantly reduced risk for type 2 diabetes, regardless of whether the coffee is caffeinated or not, findings from a metaanalysis of 28 prospective studies indicate.

Consuming one cup of coffee per day of regular coffee was associated with a 9% reduction in diabetes, whereas drinking one cup of decaf was associated with a 6% reduction (the difference between the two types was not statistically significant), Frank B. Hu, MD, PhD, a professor of nutrition and epidemiology at Harvard School of Public Health in Boston, Mass., and colleagues reported in Diabetes Care.

The preventative benefits off coffee-drinking appear to increase in a dose-response fashion, with type 2 diabetes risk falling 33% among those who drank six cups per day, the researchers noted.

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Although the benefits of coffee on diabetes risk have been reported in previous studies, Hu and colleagues set out to examine differences in caffeinated vs. decaffeinated coffee.

The 28-study analysis involved 1,109,272 participants, of whom 45,335 developed diabetes during follow-up.

The relative risk for type 2 diabetes with coffee consumption, compared with no or rare consumption, ranged from 0.92 for 1 cup per day, 0.85 for 2 cups, 0.79 for 3 cups, 0.75 for 4 cups, 0.71 for 5 cups, and 0.67 for 6 cups.

Meanwhile, the relative risk for diabetes associated with 1 cup of caffeinated coffee per day (compared to no or rare coffee consumption) was 0.91 compared with 0.94 for 1 cup of decaffeinated coffee per day ( P = .17).

“Coffee consumption was inversely associated with the risk of type 2 diabetes in a dose-response manner,” the researchers wrote. “Both caffeinated and decaffeinated coffee was associated with reduced diabetes risk.”

Coffee contains chlorogenic acid, a phenolic compound that’s been shown to improve insulin sensitivity and reduce blood sugar absorption, the researchers pointed out. They called for further studies to determine the underlying protective mechanisms.


  1. Ding M et al. Diabetes Care. 2014;37(2):569-586.