Conflicting Evidence: The Health Benefits of Beta-carotene

Enlarge Image Image Gallery Bright orange foods such as sweet potatoes and carrots are natural sources of potentially cancer-preventing beta-carotene. Photo by Slice of Chic/ Courtesy Flickr: http://www.flickr.com/photos/sliceofchic/5347151255/sizes/m/

Beta-carotene

In 1996, the news media reported the results of three studies on beta-carotene, a nutrient purported to be rich in disease-fighting elements. But the news wasn’t good: the incidence of lung cancer among study volunteers actually increased while they were taking beta-carotene supplements.

Although scientists found flaws in the studies almost immediately, the bad news traveled quickly. A Forbes magazine article stated that all supplements may be a waste of money and that the Nobel Laureate and vitamin C researcher Linus Pauling might “still be alive today if not for those damn [vitamin C] pills.” (1) Pauling died at age ninety-three in 1994.

However, more than 200 studies have shown that beta-carotene can protect against cancer, stroke, and heart disease, as well as decrease cholesterol levels. So what’s the fuss about?

Three studies, three controversies

Beta-carotene is a pigment found in milk, some yellow and dark green vegetables such as broccoli, spinach, and carrots, and in fruits such as cantaloupes, peaches, and apricots. In the body, beta-carotene is converted into vitamin A, essential for normal eyesight, healthy tissue, strong immunity, and bone development.

Although the bulk of studies conducted on beta-carotene show that it does prevent disease, the three recent studies contradict those findings.

In the first study, known as the Physician’s Health Trial, 22,000 U.S. physicians took either 50 mg of beta-carotene or 325 mg of aspirin every other day for twelve years, ending in 1995. The results: No significant differences among the participants in incidence of cancer, heart disease, or overall mortality. Head researcher Charles H. Hennekens, M.D., of Harvard Medical School and Brigham and Women’s Hospital in Boston, stated in a National Cancer Institute press release that “beta-carotene supplementation is not a magic bullet—it can neither substitute for a good diet nor compensate for a bad one.”

The second study, the Beta-Carotene and Retinol Efficacy Trial, involved 18,000 U.S. volunteers aged fifty to sixty-nine who were smokers or former smokers or who had been extensively exposed to asbestos as determined by chest X-ray. Smokers and former smokers had smoked enough cigarettes to equal at least one pack a day for twenty years. From 1993 to 1996, half of the participants took 30 mg of beta-carotene plus 25,000 IU of vitamin A daily and the other half took a placebo. Those taking the beta-carotene and vitamin A had 28 percent more lung cancers and 17 percent more deaths than those taking the placebo, the study showed.