A pot of gold: Coffee's clean bill of health

September 14, 1995|By Jane E. Brody | Jane E. Brody,New York Times News Service

With coffee bars proliferating from Seattle to Baltimore, and the specialty coffees they feature promising to turn around a decades-long decline in American coffee consumption, the news about coffee's effects on health is surprisingly good.

A substantial amount of research, including several large studies done in the last few years, has turned up little solid scientific evidence to indict a moderate intake of coffee or caffeine as a serious or even minor health threat.

"Some of the most serious hazards that were linked to caffeine in the past have not panned out," said Dr. James L. Mills, who studies caffeine's effects on pregnancy at the National Institute of Child Health and Human Development in Bethesda.

After peaking in 1962 at 3.12 cups per person a day, coffee consumption endured a 30-year slide in popularity, finally stabilizing in the mid-1990s around 1.7 cups, according to a survey conducted last winter by the National Coffee Association.

Of course, caffeine is also present in black and green teas and in soft drinks. Eighty percent of Americans consume at least one beverage containing caffeine every day, and among Americans over 18, the per-capita consumption of caffeine is about 200 milligrams a day.

Dr. Mills noted that heavy consumers of caffeine -- those who drink eight or more 5-ounce cups of coffee a day -- tend to be "very overworked, driven people who are generally not the best health risks."

For the average healthy person, about the most serious charge science can levy against caffeine is that it may be addictive. After 18 to 24 hours, its absence, even in those who consume it moderately, sometimes results in withdrawal symptoms, including severe headaches, fatigue, depression and poor concentration.

Concerns about the effects of caffeine on pregnancy and fetal development also persist.

Despite a score of studies on the relationship between caffeine and a woman's ability to conceive and deliver a full-term, full-size, healthy infant, researchers are still arguing about the reproductive risks of even relatively high doses of caffeine before or during pregnancy. All relevant studies have suffered from one or more methodological limitations that might invalidate their findings, scientists say.

While moderate consumption -- usually defined as two to four 5-ounce cups of coffee daily -- has thus far received a relatively clean bill of health even in people at high risk for developing heart disease or cancer, new studies have linked heavier daily intakes to heart attacks and bone loss in women.

In men with mild high blood pressure, several recent studies have shown that a significant rise in blood pressure can occur after just two or three cups of coffee, especially if caffeine is consumed before exercising.

Along with these cautionary findings has come encouraging news about caffeine's potential role in weight control.

Caffeine raises the rate at which the body burns calories for three or more hours after it is consumed, according to studies of healthy volunteers of normal weight in Denmark. Just 100 milligrams of caffeine -- the amount in one cup of coffee or two cans of cola -- can raise the metabolic rate by 3 to 4 percent, and larger intakes raise it even higher. If the consumer also exercises, the caloric burn stimulated by caffeine is greater still. But caffeine is no free lunch for dieters because it also effects the release of insulin, causing blood sugar to fall, which induces hunger pangs.

Caffeine, known chemically as 1,3,7-trimethylxanthine, is one of a class of methylxanthine compounds found in 63 plant products, including tea leaves, cocoa beans and coffee beans.

Similar to amphetamines but milder in its effects, caffeine stimulates the sympathetic nervous system, which regulates the body's automatic functions. As a central nervous system stimulant, it makes people feel more alert, temporarily relieves fatigue and promotes quick thinking. Its contrary effects on blood vessels often render it medically useful: it dilates arteries feeding the heart, increasing blood flow, and constricts arteries in the head, helping to counter migraine headaches.

The other chemicals

But caffeine is only one, albeit the best known, of about 500 chemicals in coffee. Indeed, caffeine was recently absolved of at least one of coffee's reputed ill effects -- the ability to raise serum cholesterol levels. That drawback, researchers in the Netherlands say, stems not from caffeine but from the oils in coffee beans that are extracted when the grounds are boiled. Those oils are not a problem when coffee is brewed through a paper filter, because the oils are left behind.

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