Dr. Tim Says....

More Good News for Coffee Drinkers

About a month ago I shared with you an article regarding the long-term effects of caffeine intake among women. That study indicated that not only does caffeinated coffee not cause hypertension, drinking more caffeinated coffee (rather than only a cup or two a day) may actually help prevent hypertension.

Now I have even more good news for those who drink caffeinated coffee. A recent study published in the Journal of the American Medical Association (JAMA, 2005; 294: 97- 104) analyzed multiple existing studies performed both within the United States and in Europe in an effort to discover any connection between coffee intake and the risk of type 2 diabetes (adult-onset diabetes).

In an effort to standardize the various levels of coffee intake defined in the multiple studies, the researchers defined the following categories of consumption for studies performed in the United States versus those in Europe:

United States Studies	European Studies
6 cups or more of coffee per day	7 cups or more of coffee per day
4-5 cups per day	5-6 cups per day
1-3 cups per day (or 3 or more)	4-5 cups per day
0 cups per day	2 or less cups per day

The long-term studies included in their analysis ranged from 6 to 20 years in length, and the study outcomes were adjusted for age, BMI (Body Mass Index), sex, and physical activity, among others.

Even though higher coffee consumption was generally associated with a less healthy lifestyle, those who drank the most coffee (6 cups or more per day) had the lowest risk of type 2 diabetes: a 35% lower risk than those who were in the control groups of no coffee (in the US) or 2 or less cups of coffee per day (in the European studies). Those who were in the second-highest level of consumption had a risk reduction of 28%.

But is it the caffeine, or the coffee that has the positive effect? It appears that it's the coffee.

The studies performed in the US differentiated between decaffeinated and caffeinated coffee because drinking decaffeinated coffee is far more prevalent in the US than elsewhere. The inverse association between coffee intake and risk of type 2 diabetes remained. A study performed in Japan differentiated between caffeinated coffee and caffeine alone, and the inverse association was stronger for the coffee than for the caffeine. Even more interesting, a study performed in Finland differentiated between the type of coffee the study participants drank: drip-filtered coffee (the kind most people in the US drink) versus pot-boiled coffee (i.e., press-pot/French press or Turkish coffee). Finnish risk for type 2 diabetes was higher for those who drank pot-boiled coffee than for those who drank drip-filtered coffee.

Why would coffee have such an effect on our risk of type 2 diabetes? We don't know for sure. Coffee contains a number of different substances other than caffeine that have been shown to have an effect on antioxidant levels, glucose levels, and insulin sensitivity, Further studies will need to be performed to determine just which combination of chemicals has the effect on type 2 diabetes, but in the mean time, the good news is that you still have a green light to continue drinking coffee.

December 26, 2005

Last updated: 02/02/06