High consumption of coffee, tea appears to decrease risk for diabetes

Drinking three to four cups of tea and regular or decaffeinated coffee per day was associated with a 5% to 10% lower risk for diabetes, according to a new meta-analysis published in the Archives of Internal Medicine.

Adults who consumed more than three to four cups of coffee — regular or decaffeinated — per day had a 25% lower risk for diabetes compared with those who consumed no more than two cups per day (RR=0.76; 95% CI, 0.69-0.82). Each additional cup of coffee consumed daily was associated with a 7% decreased risk for diabetes (RR=0.93; 95% CI, 0.91-0.95).

For decaffeinated coffee, researchers identified about a one-third lower risk for diabetes among adults who consumed more than three to four cups per day vs. those who consumed none (RR=0.64; 95% CI, 0.54-0.77).

Results were similar for tea consumption — about a one-fifth lower risk for diabetes among drinkers of more than three to four cups per day vs. those who drank none (RR=0.82; 95% CI, 0.73-0.94).

Researchers pooled data on 18 studies during 1966 and 2009 including 457,922 participants that examined the association between coffee consumption and risk for diabetes. Six studies included 225,516 participants and assessed the association with decaffeinated coffee; seven studies included 286,701 participants and assessed the association with tea consumption.

Cohorts consisted of predominantly whites (21% Asian) and included 21,897 people with new-onset diabetes.

“If such beneficial effects were observed in interventional trials to be real, the implications for the millions of individuals who have diabetes or are at future risk of developing [diabetes] would be substantial,” the researchers wrote.

The researchers noted that the association is unlikely to be solely related to caffeine due to the association between decaffeinated coffee and diabetes risk.

“Other compounds in coffee and tea, including magnesium and lignans, may be involved,” they wrote.

“Owing to the presence of small-study bias, our results may represent an overestimate of the true magnitude of the association,” the researchers concluded. “The putative protective effects of these beverages warrant further investigation in randomized trials.”

Huxley R. Arch Intern Med. 2009;169:2053-2063.

Coffee helps, but other things are even more important. Those who are overweight should reduce their body weight by 5% to 10% and include physical activity such as a brisk walk for 30 minutes a day. Then those people who are at risk of developing diabetes will reduce this risk by 40% to 50%. It is interesting to consider why a beverage like coffee has a beneficial effect. It is obviously not the caffeine, as decaffeinated coffee has the same efficiency as caffeinated coffee. Coffee may contain antioxidants but the studies have not measured the number of chemicals in the blood which is important.

– Lars Rydén, MD, PhD

Professor in Cardiology, Department of Medicine, Solna,
Karolinska University Hospital, Stockholm, Sweden