Re-javanation: That cuppa joe might have some health benefits

Content provided by the Faculty of the Harvard Medical School

Re-javanation: That cuppa joe might have some health benefits

Is coffee a health drink? Not quite, but some research suggests that it could protect against diabetes and other conditions.

Don’t you love it when this happens? Something that was bad for you, or at least questionable, turns out to have health benefits. It’s happened with chocolate (although the claims for chocolate are going a little too far) and alcohol (although only in moderation). Now it seems to be coffee’s turn.

Study findings from 2004 and 2005 suggest it might actually be good for us. A 2005 article in the British Journal of Nutrition asked whether coffee should be considered a “functional food” — one that has health benefits beyond basic nutrition.

Coffee hasn’t been completely exonerated. Pregnant women still avoid caffeinated coffee because of fears about fetal health and miscarriage that date back to studies published over 20 years ago. Whether those fears are warranted is still unclear, but why take a chance?

The cardiovascular vote is split. Coffee contains antioxidants that may offer some protection, and research is showing that it reduces the likelihood of developing diabetes, which is itself a major heart disease risk factor. But it also increases homocysteine levels and may have negative effects on the aorta. In general, when a risk factor has been carefully studied and the results flip back and forth like this, it often means that if there is any harm or benefit, it’s pretty minor.

Here’s a rundown of some of the—mostly good—news about coffee.

Blood pressure. True, a cup of coffee can temporarily kick up your blood pressure. Coffee also tends to increase the level of certain stress hormones, including cortisol and epinephrine (adrenaline), and when that happens, blood pressure tends to rise.

But results from prospective studies — which follow people for years, not just a few weeks — are showing that coffee doesn’t increase the risk for high blood pressure (hypertension). In November 2005, Harvard researchers reported results from the Nurses’ Health Study that showed no coffee-hypertension link. It’s possible that people develop a tolerance to coffee’s hypertensive effects after a while.

Cancer. Several studies suggest that coffee has anti-cancer properties. Japanese researchers in 2005 concluded that coffee drinkers were 50% less likely to get liver cancer than nondrinkers (coffee may protect people against other forms of liver disease as well). It’s been linked to reduced colon cancer risk. But you can’t make a sweeping generalization. One study found that coffee reduces breast cancer risk in lean women, but increases it in heavier women. In 2005 Harvard researchers reported that decaf coffee seemed to lower rectal cancer risk, while caffeinated coffee had no effect on colon or rectal cancer. Several studies have shown that caffeinated and decaffeinated coffee have different health effects (see chart).

Cholesterol. Two substances in coffee — kahweol and cafestol — raise cholesterol levels. Since paper filters capture these substances, your regular cup of coffee wasn’t a problem. But now Americans are drinking gallons of unfiltered coffee as they quaff cappuccino, lattes, and assorted espresso-based drinks.

Research presented at the American Heart Association meeting in November 2005 added a new wrinkle. A tightly controlled study of 187 people linked cholesterol increases to decaffeinated — but not to caffeinated — coffee. The investigators attributed decaf’s cholesterol-raising effect not to its lack of caffeine, but to the type of bean used in making it.

Diabetes. Normally, insulin serves as a guide for blood sugar, ushering it into cells. Short-term studies show that coffee — maybe caffeine, in particular — makes cells less sensitive to insulin’s entreaties on blood sugar’s behalf. Insulin resistance, as it is called, can lead to higher blood sugar and insulin levels and, eventually, diabetes.

Now several long studies have shown that heavy coffee drinkers may be half as likely to get diabetes as light or nondrinkers. Why? Possibly because coffee contains ingredients (such as chlorogenic acid) that lower blood sugar. A coffee habit may also increase your resting metabolism rate, which could help keep diabetes at bay.

Gallstones. Researchers report that coffee drinkers are less likely to suffer symptomatic gallstone disease, possibly because coffee alters the cholesterol content of the bile produced by the liver.

Parkinson’s disease. Coffee seems to protect men but not women against Parkinson’s disease. If caffeine is the reason, one possible explanation for the sex difference may be that estrogen and caffeine need the same enzymes to be metabolized, and estrogen hogs those enzymes. Supporting this hypothesis are findings that women who’ve never used postmenopausal hormones are less likely to get Parkinson’s disease if they drink coffee.

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Last updated:	August 21, 2006