Heart Disease and Stroke continued...
First, there's the potential effect on type 2 diabetes risk. Type 2 diabetes makes heart disease and stroke more likely.
Besides that, coffee has been linked to lower risks for heart rhythm disturbances (another heart attack and stroke risk factor) in men and women, and lower risk for strokes in women.
In a study of about 130,000 Kaiser Permanente health plan members, people who reported drinking 1-3 cups of coffee per day were 20% less likely to be hospitalized for abnormal heart rhythms (arrhythmias) than nondrinkers, regardless of other risk factors.
And, for women, coffee may mean a lower risk of stroke.
In 2009, a study of 83,700 nurses enrolled in the long-term Nurses' Health Study showed a 20% lower risk of stroke in those who reported drinking two or more cups of coffee daily compared to women who drank less coffee or none at all. That pattern held regardless of whether the women had high blood pressure, high cholesterol levels, and type 2 diabetes.
Parkinson’s and Alzheimer's Diseases
“For Parkinson’s disease, the data have always been very consistent: higher consumption of coffee is associated with decreased risk of Parkinson’s,” Hu tells WebMD. That seems to be due to caffeine, though exactly how that works isn't clear, Hu notes.
Coffee has also been linked to lower risk of dementia, including Alzheimer’s disease. A 2009 study from Finland and Sweden showed that, out of 1,400 people followed for about 20 years, those who reported drinking 3-5 cups of coffee daily were 65% less likely to develop dementia and Alzheimer’s disease, compared with nondrinkers or occasional coffee drinkers.
The evidence of a cancer protection effect of coffee is weaker than that for type 2 diabetes. But “for liver cancer, I think that the data are very consistent,” Hu says.
“All of the studies have shown that high coffee consumption is associated with decreased risk of liver cirrhosis and liver cancer,” he says. That's a "very interesting finding," Hu says, but again, it's not clear how it might work.
Again, this research shows a possible association, but like most studies on coffee and health, does not show cause and effect.