Beta-CaroteneDaily Value: None
Good Food Sources: Sweet potatoes, carrots, cantaloupe, spinach and other dark green, leafy vegetables
Beta-carotene has frequently been portrayed as the blockbuster nutrient that will save the world from cancer, heart disease, aging, cataracts and a host of other ills.
And it may well be. Preliminary studies over the past few years have indicated that the more beta-carotene-rich fruits and vegetables people eat, the less likely they are to get cancer--particularly cancers of the lung, stomach, esophagus, mouth and, in women, the reproductive tract.
In the Physicians' Health Study at Harvard Medical School, for example, a preliminary report indicates that heart attack risk was cut 50 percent in a group of men between the ages of 40 and 84 who took 50 milligrams (83,000 international units) of beta-carotene every other day.
But in 1994, researchers began to question the therapeutic effects of beta-carotene. A study of 29,000 male Finnish smokers found that men who took 20 milligrams (about 33,000 international units) of beta-carotene a day actually had an increased incidence of both lung cancer and heart disease.
"It was an unexpected result," admits Norman Krinsky, Ph.D., professor of biochemistry in the Department of Biochemistry at Tufts University School of Medicine in Boston. "It does not coincide with what people had expected."
Some scientists suspect that the unexpected increase in heart disease and lung cancer among the Finns may have been caused by one or the other of two problems. First, the smokers had been puffing away on cigarettes for so many decades--three, to be exact--that the cancer process had been initiated even before researchers started handing out beta-carotene. Second, the heavy drinking in which the smokers also had apparently engaged--and which was not reported in the original study--may have influenced the effectiveness of the beta-carotene, according to Joanne Curran-Celentano, Ph.D., associate professor of nutritional sciences at the University of New Hampshire in Durham. Dr. Curran-Celentano cautions that the Finnish study is not suggesting that beta-carotene supplementation caused an increase in cancer or in heart disease. Poor diet and long-term heavy smoking and drinking may have put the men at high risk, she says.
Many researchers and physicians still recommend fruits and vegetables rich in carotenoids for disease, according to Dr. Krinsky. In light of the Finnish study, however, some researchers may be more cautious about recommending beta-carotene supplements.
Contributing to their reluctance and caution in recommending supplements are relatively new laboratory techniques that have revealed that most foods containing beta-carotene also contain other powerful disease-fighting members of the carotenoid family such as alpha-carotene, lycopene, zeaxanthin and lutein. In fact, says Dr. Krinsky, it may be these substances that have been doing most of the disease-preventive work, while beta-carotene has been garnering all of the credit.
Using Beta-Carotene Safely
People should be reaching for carotenoid-rich foods rather than supplements," says Dr. Krinsky. "But for those among us who do not take in five to nine servings of dark green, leafy vegetables and yellow fruits and vegetables a day, it might be wise to supplement the diet with a moderate dose of beta-carotene--maybe 5, 10 or 15 milligrams (between 8,000 and 25,000 international units) a day." With respect to the question about whether or not to supplement, there is no easy answer, he says.
Too much beta-carotene in the body can turn the skin orange. The discoloration fades as levels of the nutrient return to normal.