According to the LA Times, “a spate of high-profile studies published in the last few years shows that a variety of popular supplements — including calcium, selenium, and vitamins A, C and E — don’t do anything to reduce the risk of developing heart disease, stroke, or a variety of cancers.” And, the New York Times is reporting, “In the past few years, several high-quality studies have failed to show that extra vitamins, at least in pill form, help prevent chronic disease or prolong life.” But what about multivitamins? Are they helpful or harmful
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Multivitamins, the combination pills, which contain 10 to 30 vitamins and minerals, are the most popular dietary supplements sold in America. A report published this week in the Archives of Internal Medicine suggests they shouldn’t be. 
The study tracked 161,808 participants in the Women’s Health Initiative, a long-term effort to identify risk factors for cancer, heart disease and bone health in postmenopausal women. Subjects in the nationwide study included white, black, Latina, Asian and Native American women. They were followed for an average of nearly eight years.
Overall, 41.5% of study participants took some version of a multivitamin. Those women were more likely to be white and college-educated, live in the West, exercise and have a lower body mass index.
However, women who took multivitamins weren’t any more likely to ward off a diagnosis of breast, ovarian, lung, stomach, bladder, kidney, colorectal or endometrial cancer than were women who didn’t take multivitamins. Nor were multivitamins in general helpful in preventing heart attacks, strokes, blood clots or reducing the risk of death from any cause during the study period.
Last year, a study that tracked almost 15,000 male physicians for a decade reported no differences in cancer or heart disease rates among those using vitamins E and C compared with those taking a placebo. And in October, a study of 35,000 men dashed hopes that high doses of vitamin E and selenium could lower the risk of prostate cancer. 
The research team, led by scientists at the Fred Hutchinson Cancer Research Center in Seattle, did find one modest benefit: The 3,741 women who took stress multivitamins — formulations with higher doses of several B vitamins along with an extra jolt of vitamin C — were 25% less likely to have a heart attack. No other correlations between vitamins and health outcomes were statistically significant.
The study provides convincing evidence that multivitamin use has little or no influence on the risk of common cancers, cardiovascular disease or total mortality in postmenopausal women, the authors wrote.
So, they wondered, “Why do millions of Americans use a daily multivitamin for chronic disease prevention when the supporting scientific data are weak?”
In January, an editorial in The Journal of the National Cancer Institute noted that most trials had shown no cancer benefits from vitamins — with a few exceptions, like a finding that calcium appeared to lower the recurrence of precancerous colon polyps by 15 percent.
But some vitamin studies have also shown unexpected harm, like higher lung cancer rates in two studies of beta carotene use. Another study suggested a higher risk of precancerous polyps among users of folic acid compared with those in a placebo group.
In 2007, The Journal of the American Medical Association reviewed mortality rates in randomized trials of antioxidant supplements. In 47 trials of 181,000 participants, the rate was 5 percent higher among the antioxidant users. The main culprits were vitamin A, beta carotene and vitamin E; vitamin C and selenium seemed to have no meaningful effect.
Some physicians continue to recommend them as a backstop for patients whose diets may contain nutritional gaps. And since they don’t require a prescription, many people simply assume they are safe.
But those assumptions may not be warranted, especially if people wind up overdosing on vitamins and minerals, the researchers wrote.
Nevertheless, there are vitamins that may be helpful. Calcium can strengthen bones, reduce the risk of fractures, and reduce the risk of colon polyps or perhaps colon cancer. And, as readers to this website know, there have been dozens of studies published this last year on the benefits of vitamin D (leading the American Academy of Pediatrics to double the recommended daily dose for children and teens).
“Vitamin D looks really promising,” said Dr. JoAnn E. Manson, the chief of preventive medicine at Brigham and Women’s Hospital and an investigator on several Harvard vitamin studies told the New York Times. “But we need to learn the lessons from the past. We should wait for large-scale clinical trials before jumping on the vitamin bandwagon and taking high doses.”