Hopkins Insider: Waking Up To Coffee's Effects
December 30, 1998
By Michael J. Klag, M.D., M.P.H.
Is it the caffeine that's linked to heart disease... or the way it's prepared?
BALTIMORE (Johns Hopkins Health Insider) - With concern growing about the possible impact caffeine can have on your health, you may wonder whether your choice in coffee should be "regular" or "decaf." But the real question for the cholesterol-conscious is how their morning cup is prepared.
More than 50 years ago, Hopkins began a still ongoing study that identified coffee, among other factors, as a risk factor for heart attack. This study added fuel to an already controversial fire on the relationship between coffee and coronary heart disease. Other studies in the U.S. and abroad seemed to confirm these findings.
But what made our study particularly valuable was that, because of its long follow-up, it was able to track the risks of coffee drinking through various periods in time: Beginning in 1975 and continuing to the present, there was no increased risk associated with coffee drinking in our study. That finding is consistent with data from other studies.
Other American studies showed no increased risk of heart disease from drinking coffee, while European studies tended to show that coffee-drinkers had higher rates of heart disease.
Why? It's not the caffeine -- as many people assume. Rather, it's likely because of the way the coffee is prepared.
The studies showing no increased risk were done after drip coffee became popular in the U.S. Prior to that, most Americans were drinking percolated coffee, while Europeans were drinking boiled coffee, as they still do.
When boiled or percolated, consumed coffee can raise serum cholesterol levels. We think it is a result of hot water and coffee grounds combining to create oils called "terpenes."
Research shows that like some other oils, terpenes can raise blood cholesterol when ingested. And the longer the hot water and coffee grounds are in contact with each other -- as with boiled and percolated coffee -- the more terpenes are produced.
The increase in overall cholesterol levels from drinking boiled or percolated coffee varies from person to person, but it averages about 12 mg/dl. An overall reading of below 200 mg/dl is considered healthy.
With filtered drip coffee, however, we see no such increase in cholesterol because the water speeds through coffee grounds more quickly, producing fewer terpenes. Using a paper filter seems to be even more protective, as the filter absorbs some of the terpenes.
In fact, to date researchers have found no evidence that caffeine itself raises cholesterol levels or directly influences risk of heart attack. However, caffeine can produce a sudden but temporary increase in blood pressure and heart rate, and studies suggest that people with hypertension can lower their blood pressure by cutting out caffeine. Also, if you have irregular heart rhythms, you may exacerbate the problem by consuming caffeine. Remember, caffeine is also found in teas, colas and chocolate, as well as coffee.
Michael J. Klag, M.D., M.P.H., the David M. Levine Professor of Medicine and Director of the Division of General Internal Medicine at the School of Medicine, is a noted researcher of coffee and its impact on heart disease.
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