“Stop wasting money on vitamin and mineral supplements,” declared a leading medical journal. “Enough is enough.”
The journal was reacting to two disappointing studies on multivitamins. In the first, doctors who were given a daily multivitamin (Centrum Silver) for 12 years did no better on memory tests than those who got a placebo. In the second, heart attack patients who got a multivitamin for one to five years were no less likely to have a second heart attack than those who got a placebo (though half the patients stopped taking the pills before the study ended).
It may be sensible for some people to not bother with multivitamins, especially if they’re paying top dollar for overpriced pills. But it’s not good advice for women who are or may become pregnant or for men or women whose diets run short on key nutrients.
multivitamins and the prevention of cancer
“To say that multivitamins have no benefit is an oversimplification,” says JoAnn Manson, professor of medicine at Harvard Medical School. “The Physicians’ Health Study II found a significant reduction in cancer incidence.”
In that trial—which randomly assigned roughly 14,600 men aged 50 or older to take Centrum Silver or a placebo for 11 years—the vitamin takers had an 8 percent lower risk of cancer than those who took the placebo.
The researchers didn’t find a drop in any single cancer, especially prostate cancer, the one most likely to strike older men. But that may not mean much.
“The launch of the study occurred just as PSA screening for prostate cancer was increasing,” explains Manson. “So this screening was picking up mostly early prostate cancers before there was time to see any effect of the vitamins, plus the large number of prostate cases dwarfed other cancers.”
In fact, the study found a 12 percent lower risk of cancers other than prostate.
more important for older men?
There were hints in the Physicians’ Health Study II that vitamins may have mattered more to some men than others.
“When we looked at results by age group, we saw that men 70 and older experienced an 18 percent reduction in cancer,” notes Manson. “And there was a similar reduction in cancer in the men who had a lower intake of fruits and vegetables when they entered the study.”
The trial also found a 27 percent lower risk of a new cancer in men who had been previously diagnosed with cancer.
“So overall, there was a benefit from multivitamins in men who were less likely to have a healthful diet and in older individuals who often have problems with absorption, medications, or illnesses that could interfere with optimal nutritional status,” explains Manson.
what about people who aren’t male physicians?
Doctors are typically healthier than the average American. “Physicians are not representative of the overall population,” says Manson. “They tend to have better diets and higher socioeconomic status, so they’re probably the least likely group to benefit from multivitamins.”
And the Physicians’ Health Study II tested men only.
“How can we not do a trial that evaluates multivitamins in women?” asks Manson. “At least a third of women take multivitamins regularly. We need to know the benefits and risks.”
We may find out in a few years. Manson is co-directing a new trial—the COcoa Supplement and Multivitamins Outcomes Study (COSMOS)—which will give cocoa flavanols or a placebo to 18,000 women (aged 65 or older) and men (aged 60 or older) for four years. It will also give them either Centrum Silver or a placebo. The trial will look at cognitive function, diabetes, physical performance, and other outcomes. Stay tuned.
earlier vitamin supplement studies
But what about earlier trials of vitamins that came up empty…or found that people who took vitamins had a higher risk of disease?
“Other vitamin supplement trials have usually tested a megadose of an isolated micronutrient, which is not ideal,” says Manson.
“For example, taking very high doses of beta-carotene may interfere with the absorption or bioavailability of other carotenoids that may be more important than beta-carotene. And some antioxidant vitamins—like vitamin E— can be pro-oxidants at high levels.”
Testing a basic multivitamin is different.
“It has more than 20 vitamins and minerals at levels that prevent nutritional deficiencies,” says Manson. “So it’s more likely to reduce the risk of cancer in individuals who have suboptimal diets.”
The bottom Line: It may be worth taking an ordinary multivitamin to get enough vitamin D, vitamin B-12, and (if you could become pregnant) folic acid. A multi may also lower the risk of cancer in men, but the jury is still out in women.
Sources: Ann. Intern. Med. 159: 806, 2013; Ann. Intern. Med. 159: 797, 2013; Ann. Intern. Med. 159: 850, 2013; JAMA 308: 1871, 2012.
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