Vitamin supplements won't protect people against lung cancer and taking vitamin E may even heighten the risk, a new study finds.
The survey covered the supplement-taking habits and lung cancer incidence of almost 78,000 adults in the state of Washington over a four-year period.
"Our study of supplemental multivitamins, vitamin C, vitamin E and folate did not show any evidence for a decreased risk of lung cancer," study author Dr. Christopher G. Slatore, a fellow in the division of pulmonary and critical care medicine at the University of Washington, said in a statement. "Indeed, increasing intake of supplemental vitamin E was associated with a slightly increased risk of lung cancer."
As reported in the March issue of the American Journal of Respiratory and Critical Care Medicine, the research focused on men and women aged 50 to 76 taking part in the four-year VITAmins and Lifestyle (VITAL) study. Lung cancer was diagnosed in 521 participants surveyed.
In addition to the expected association with smoking, family history and other lung cancer risk factors, there was a slight but statistically significant association with vitamin E supplementation and incidence of the disease, the researchers found.
Every increase in vitamin E of 100 milligrams per day was associated with a 7 percent rise in lung cancer risk -- translating into a 28 percent increase in risk over 10 years for someone taking 400 milligrams of vitamin E daily.
"This provides additional evidence that taking vitamin supplements does not help prevent lung cancer," said Eric Jacobs, strategic director of pharmacoepidemiology at the American Cancer Society.
The society does not currently recommend use of any vitamin supplement to prevent malignancy, Jacobs said. However, "our dietary guidelines do recommend eating five or more servings of a variety of vegetables each day," he noted.
A representative of the supplements industry called the study results "not all that surprising."
"Vitamins are essential nutrients that act to maintain health and prevent vitamin deficiency," Pamela Mason, spokeswoman for the London-based Health Supplements Information Service, said in a statement. "They were never intended to be used to prevent chronic disease such as cancer. Indeed, it would be asking a lot of a vitamin pill to expect it to prevent cancer."
Since the primary cause of lung cancer is smoking, the best preventive measure is simply not to smoke, Jacobs said. Nutrients can play an auxiliary role, he noted. Anyone who cannot quit should avoid taking beta-carotene supplements, because studies have linked them to an increased risk of lung cancer, Jacobs said.
On the other hand, "for former smokers, there is some evidence that vegetables high in carotinoids, such as carrots and sweet peas, decrease the risk," he said.
Some vitamins have been linked to a reduced risk of other cancers, added Edward Gorham, an associate professor of family and preventive medicine at the University of California at San Diego.
"We have worked with vitamin D, and we found a protective effect of vitamin D on colon cancer, breast cancer and ovarian cancer, and recently a modest effect on lung cancer," Gorham said.
But that effect came not from supplements but from sunlight, which causes vitamin D to be formed in the human body, he said.
"These results with multivitamins dont surprise me because there is so little vitamin D in multi-supplements, 100 or 200 International Units," Gorham said. "To achieve the effect, it takes 2,000 IU. If youre in the tropics, that amounts to 10 or 15 minutes in the sun. In southern California, it takes 10 or 15 minutes in the summer and longer in the winter because the sun angle is so low."
One study has also associated vitamin D supplements with a decreased risk of colon and breast cancer in women, Gorham said.
SOURCES: Eric Jacobs, Ph.D., strategic director, pharmacoepidemiology, American Cancer Society, Atlanta; Edward Gorham, Ph.D., associate professor, family and preventive medicine, University of California, San Diego; Feb. 29, 2008, statement, American Thoracic Society; Feb. 29, 2008, statement, Health Supplements Information Service; March 2008 American Journal of Respiratory and Critical Care Medicine