Blood pressure. Results from long-term studies are showing that coffee may not increase the risk for high blood pressure over time, as previously thought. Study findings for other cardiovascular effects are a mixed bag.
Cancer. Coffee might have anti-cancer properties. Last year, researchers found that coffee drinkers were 50% less likely to get liver cancer than nondrinkers. A few studies have found ties to lower rates of colon, breast, and rectal cancers.
Cholesterol. Two substances in coffee — kahweol and cafestol — raise cholesterol levels. Paper filters capture these substances, but that doesn’t help the many people who now drink non-filtered coffee drinks, such as lattes. Researchers have also found a link between cholesterol increases and decaffeinated coffee, possibly because of the type of bean used to make certain decaffeinated coffees.
Diabetes. Heavy coffee drinkers may be half as likely to get diabetes as light drinkers or nondrinkers. Coffee may contain chemicals that lower blood sugar. A coffee habit may also increase your resting metabolism rate, which could help keep diabetes at bay.
Parkinson’s disease. Coffee seems to protect men, but not women, against Parkinson’s disease. One possible explanation for the sex difference may be that estrogen and caffeine need the same enzymes to be metabolized, and estrogen captures those enzymes.
Drinking more than four cups of coffee a day, however, may increase the risk of heart problems. In fact, a new study suggests that even two six-ounce cups of coffee a day may increase blood test values that measure inflammation.
If future research confirms these findings, there may be cause for concern. But it’s too early to severely limit your coffee consumption for this reason, because two large American studies show no effect of coffee or caffeine on the incidence of heart disease.