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America’s favorite dietary supplements, multivitamins, modestly lowered the risk for cancer in healthy male doctors who took them for more than a decade, the first large study to test these pills has found.
The result is a surprise because many studies of individual vitamins have found they don’t help prevent chronic diseases and some even seemed to raise the risk of cancer.
In the new study, multivitamins cut the chance of developing cancer by 8 percent. That is less effective than a good diet, exercise and not smoking, each of which can lower cancer risk by 20 percent to 30 percent, cancer experts say.
Multivitamins also may have different results in women, younger men or people less healthy than those in this study.
“It’s a very mild effect and personally I’m not sure it’s significant enough to recommend to anyone” although it is promising, said Dr. Ernest Hawk, vice president of cancer prevention at the University of Texas MD Anderson Cancer Center and formerly of the National Cancer Institute.
“At least this doesn’t suggest a harm” as some previous studies on single vitamins have, he said.
The study was was published online in the Journal of the American Medical Association.
About one-third of U.S. adults and as many as half of those over 50 take multivitamins. They are marketed as a kind of insurance policy against bad eating. Yet no government agency recommends their routine use “regardless of the quality of a person’s diet,” says a fact sheet from the federal Office of Dietary Supplements.
Some fads, such as the antioxidant craze over vitamins A and E and beta-carotene, backfired when studies found more health risk with those supplements, not less. Many of those were single vitamins in larger doses than the “100 percent of daily value” amounts that multivitamins typically contain.
Science on vitamins has been skimpy. Most studies have been observational — they look at groups of people who do and do not use vitamins, a method that can’t give firm conclusions.
Dr. J. Michael Gaziano, of Brigham and Women’s Hospital and VA Boston, led a stronger test. Nearly 15,000 male doctors who were 50 or older and free of cancer when the study started were given monthly packets of Centrum Silver or fake multivitamins without knowing which type they received.