“Men taking a multivitamin were 8 percent less likely than men taking a placebo to be diagnosed with a cancer,” says Harvard epidemiologist Howard Sesso who helped run the study which was published in 2012.
The trial, called the Physicians’ Health Study II, randomized 14,000 male physicians into two groups. One group was given Centrum Silver (a basic multivitamin-and-mineral for people 50 and older), the other group a lookalike placebo to take every day for 11 years. None of the men knew which they were getting.
Over the 11 years of the study, the multi-takers were 8 percent less likely than the placebo-takers to be diagnosed with cancer.
About half of the cancers were of the prostate, almost all of them the slow-growing kind that don’t necessarily need treatment. Taking a multi didn’t affect the risk of this cancer.
Instead, the risk was lowered for cancer in general, not for any specific ones.
“That may have been primarily because there weren’t enough cases of each cancer to detect significant differences,” says Sesso. (A study may not be able to detect a statistically significant difference if only a small number of people are diagnosed with, say, bladder or colorectal cancer.)
But it’s also possible that the lower risk of cancer in multi takers was due to chance.
“The fact that there wasn’t a clear reduction in risk for any specific cancer raises a question about whether multivitamins had an impact at all,” says the American Cancer Society’s Eric Jacobs.
Something that can prevent the disease usually affects specific cancers, not all of them, Jacobs explains.
How might a multivitamin prevent cancer? “It may mimic the dietary patterns we try to recommend, such as an increased intake of fruits and vegetables that are rich in a variety of nutrients,” says Sesso.
Source: JAMA 308: 1871, 2012.