More sood news for latte lovers comes from researchers at the Haward school of public Health (HSPH). They found that people who drink coffee on a regular basis experience a substantially lower risk for type 2 diabetes.


In a retrospective review of nine studies of coffee consumption and type 2 diabetes risk, Harvard researcher Rob M. van Dam, PhD, and his colleagues looked at 193,473 regular coffee drinkers who experienced 8,394 cases of type 2 diabetes. They excluded studies of people with type 1 diabetes and studies of short-term exposure to coffee or caffeine.

Researchers calculated the relative risk of type 2 diabetes in relation to how many daily cups of coffee the participants consumed. It turned out that the more coffee, the better…

  • The incidence of diabetes was lowest—0.65 (or between six and seven in 10)-for people who consumed the most coffee each day (six or more cups).
  • Those who drank four to six cups daily faced a slightly more than seven in 10 (0.72) incidence.
  • People who drank the least coffee (which was no consumption in US studies, and two or fewer daily cups for Europeans) had a relative risk of 0.94—or very little risk reduction.

These numbers did not differ significantly according to sex, obesity or geographic region (which in this case meant the US and Europe).

However, Dr. van Dam adds that the results were rather diverse in the lowest consumption category. He would not be surprised if future studies that are able to measure coffee consumption more precisely find a lower diabetes incidence for any amount of coffee.


These findings serve to underscore the results of an earlier HSPH study, in which men who drank more than six cups of coffee a day reduced their risk of type 2 diabetes by more than 50% in comparison with men who did not drink coffee...and women by 30% in comparison with women who were not coffee drinkers. This beneficial effect was observed independent of lifestyle choices such as smoking, exercise and obesity.

Scientists don't know exactly how coffee cuts diabetes risk. Paradoxically, caffeine reduces insulin sensitivity and raises blood sugar—both no-nos for diabetes. However, Dr. van Dam emphasizes that coffee is a complex beverage that contains numerous chemical compounds and minerals, which may have both helpful and harmful impacts on the body. Components other than caffeine—such as the antioxidants chlorogenic acid and magnesium—actually improve sensitivity to insulin and thus help lower diabetes risk. In animal studies, trigonelline and lignans improved glucose levels. Dr. van Dam adds that additional studies on effects of coffee components in humans are clearly needed.


For those who prefer decaf, coffee still packs some protection against type 2 diabetes. Although the effect appears to be more modest, some of this discrepancy may be attributed to study limitations. Decaffeinated coffee consumption was substantially lower than caffeinated coffee consumption, and this may have affected the estimates, explains Dr. van Dam. He points out that it is easier to detect larger contrasts in consumption than smaller differences. In addition, one can expect some misclassification when you ask for the amount of coffee people consume (change over time, differences in strength and cup size, etc).

Dr. van Dam notes that in a study on coffee consumption and C-peptide concentrations (a marker for insulin resistance), the association was actually similar for decaffeinated and caffeinated coffee consumption. He adds that it is currently unclear whether caffeine has detrimental effects on insulin sensitivity over the long term, because only short-term studies have been conducted. Nor is it clear if non-coffee sources of caffeine would have similar effects.


Other trials have already lined up in coffee's favor, demonstrating that it can lower the risk of liver problems, gallstones, colon cancer and Parkinson's disease. Of course, there's also a downside to coffee (which pregnant women, children and people with colitis, hepatitis and other dietary challenges should not drink), such as jitteriness, insomnia and a rapid heartbeat. (Coffee stimulates liver function, which in healthy people is fine in moderation, but those with active liver disease may have symptoms worsen when they consume coffee.)

Promising as it seems, Dr. van Dam and his colleagues do not go so far as to recommend drinking coffee to prevent type 2 diabetes. They emphasize that while coffee consumption may provide greater control over diabetes and possibly reduce the need for pharmaceuticals, it cannot replace the myriad health benefits of diet, exercise and weight management.

Many people stop drinking coffee because they think this is good for their health. Now coffee drinkers can take comfort in knowing that their daily jolt of java not only gets them up and moving, it also provides a definite health benefit.

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