For several years my wife and I have been taking beta-carotene pills in an effort to prevent heart disease.
We wonder if we should stop taking them because of the recent newspaper articles reporting that beta-carotene pills increase the risk of cancer.
Results are available from four large trials examining the health effects of supplementing the diet with beta-carotene. The only trial that showed a possible significant benefit of beta-carotene was a study of 30,000 adults in rural Linxian, China. Those taking beta-carotene had 13 percent fewer cancer deaths and 9 percent fewer deaths overall.
The subjects in this study, however, were poorly nourished RTC compared to Americans and their diet was supplemented with vitamin E and selenium as well as beta-carotene.
Two other trials involved people at high risk for cancer. The 1994 report of a study of about 29,000 Finnish male smokers showed a significant increase in lung cancer in those supplemented with beta-carotene. Just released were unpublished results from the CARET study of 18,000 U.S. men and women smokers and asbestos workers. The trial was stopped 21 months early because those taking the combination of beta-carotene and large amounts of vitamin A had a 28 percent increase in lung cancer deaths and a 17 percent increase in deaths from heart disease. These findings are worrisome, even though these increases were not statistically significant.
In the fourth study, which followed 22,000 male physicians for 12 years, supplements of beta-carotene had no effect on deaths from either lung cancer or heart disease.
(In 1988, a report from the same study showed a benefit of regular aspirin use in preventing coronary heart disease mortality.)
The findings are disappointing because a number of earlier studies had shown that individuals with the highest blood levels of beta-carotene had a decreased risk of coronary heart disease. How can we reconcile the apparent protective effects of higher blood levels of beta-carotene with the lack of benefits -- and possible harm -- from taking beta-carotene supplements?
Beta-carotene is but one of more than 500 chemically similar constituents of fruits and vegetables, so the association of high blood levels of beta-carotene with reduced heart disease risk may merely reflect a higher intake of foods containing other nutrients along with beta-carotene that provide the protection. Excessive amounts of beta-carotene may somehow block the beneficial effects of one or more of the other nutrients.
Should you and your wife continue to take beta-carotene supplements? The data suggests that it is a bad idea if you are heavy cigarette smokers.
Otherwise there is probably no risk from beta-carotene, but a possible waste of money. Instead, consider eating a low-fat diet rich in fruits and vegetables that may contain nutrients protecting against heart disease.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.
Pub Date: 3/05/96