UNIVERSITY OF TEXAS — 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 have even caused problems.

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 who are less healthy.

“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.