Beta-carotene: fluke or fate?

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It was a finding no one expected. The Physicians Health Study had a clear purpose: To find out if 325 milligrams of as aspirin could prevent heart attacks and 50 mg of beta-carotene could prevent cancer in 22,000 male doctors aged 40 to 84 who took the pills (or placebos) every other day.

After four years, the researchers stopped the aspirin component of the trial because it was clear that the aspirin had slashed the risk of first-time heart attacks by 44 percent. After six years, the beta-carotene component is still in progress.

But last year, the researchers noticed something unusual in a small group of 333 men who went into the study with signs of heart disease but not heart attacks): The ones taking beta-carotene had only half as many vascular events." In other words, while they didn't necessarily have fewer heart attacks, strokes, bypasses, or sudden cardiac deaths, when all those "events" were grouped together, the beta-carotene-takers had half as many.(1)

"The study provides the first evidence from humans to suggest that beta-carotene maY be useful in treating cardiovascular disease," says the study's director, Charles H. Hennekens of Harvard Medical School.

But Hennekens warns that it's too early to conclude that beta-carotene protects the heart. "We presented a Preliminary report to alert researchers," he explains. "So far we have nothing for doctors, and certainly nothing for the public."

A Plausible Theory. To explain how beta-carotene might stop heart attacks, researchers turn to the work of Daniel Steinberg of the University of California at San Diego (see page 9).

Steinberg has shown that adding oxygen to LDL (the "bad" carrier of cholesterol) makes it much more likely to clog arteries. And since beta-carotene is an antioxidant, it should theoretically keep LDL from becoming oxidized and arteries from becoming clogged.

But a reasonable theory isn't proof

"It's plausible, but so was the theory that coffee could cause pancreatic cancer," says Hennekens, referring to a 1981 study that was later proved wrong.

It and Hennekens' results were plagued by the same problem. "Our study was not designed to test the hypothesis that beta-carotene could slow the progress of heart disease," he explains. Like the link between coffee and cancer, "it just popped up."

Had he planned to study heart disease, Hennekens would have included more doctors math signs of it. Even though 22,000 physicians participated in the study, only 333 had those signs: stable angina (chest pain upon Physical exertion), coronary bypass surgery, or angioplasty (using a balloon to open a clogged blood vessel).

"It's possible that the results are due to chance or, alternatively, God may be trying to tell me something," says Hennekens. So far, he's not willing to bet.

Yet he can't help but point out another tantalizing observation: Of the 333 doctors, not a single one who took aspirin and beta-carotene got a heart attack.

"We would suggest that they work together," says Hennekens. "It's possible that aspirin has an effect on blood clotting, while beta-carotene might retard atherosclerosis by neutralizing oxidized LDL."

Don't Forget Females. Hennekens is now planning several new studies on beta-carotene. For example, one trial would ask 40,000 postmenopausal women over the age of 50 to take, every other day:

* 50 mg of beta-carotene and 325 mg of aspirin, or

* 600 mg of vitamin E and 325 mg of aspirin, or

* beta-carotene, vitamin E, and aspirin, or

* placebos.

After several years, the researchers would count, among other things, the number of heart attacks in each group.

In the meantime, people who want to take beta-carotene, vitamin E (another antioxidant), or aspirin should know that:

* Beta-carotene is harmless, but it turns some people's skin orange.

* Don't take aspirin regularly without checking with your physician. It can cause easy bruising and bleeding in your nose, stomach, and intestines.

* Vitamin E is relatively safe. Even at daily doses of more than 600 IU, there have been only isolated reports of problems like nausea, diarrhea, blurred vision, dizziness, and breast enlargement.

Also, remember that Hennekens' findings were on men who already had angina, by-Passes, or angioplasty. There is no human evidence that beta-carotene prevents first-time heart attacks.

Nor is there any evidence on people who had already had heart attacks, strokes, or unstable angina (which occurs not just upon exertion, but anytime).

And don't blame Hennekens if it turns out that beta-carotene doesn't work. After all ... he warned you.

(1) Circ. 82 (Suppl.): III-201, 1990.