Can multivitamins protect you from cancer?

“For a lot of people, multivitamins add an extra layer of security to ensure they’re getting at least minimum levels of essential vitamins and minerals to avoid nutritional deficiency or insufficiency, ” says Howard Sesso, associate professor of epidemiology at the Harvard T.H. Chan School of Public Health in Boston.

But can a multi also prevent disease, like cancer or heart disease? That remains an open question.

The longest, largest controlled study so far

In the Physicians’ Health Study II, Sesso and his colleagues randomly assigned more than 14,000 men aged 50 and older to take a daily Centrum Silver (one of the most popular basic multivitamin-and-minerals for seniors) or a placebo.

After 11 years, the multi takers had an 8 percent lower risk of being diagnosed with cancer (and a 9 percent lower risk of muticataracts) than the placebo takers. “And among men who had a history of cancer at the start of the trial, results suggested that the multivitamin was even stronger in preventing new cancers,” adds Sesso.

However, the multi takers were just as likely to have heart attacks or strokes, to suffer memory loss or other cognitive decline, or to die during the study. (Centrum had no role in conducting the study or interpreting the results.)

But questions remain.

“We don’t know whether the lower cancer risk found in men extends to women, or whether taking a multivitamin has stronger benefits in those with a history of cancer,” says Sesso.

COSMOS, a new clinical trial on women aged 65 or older and men aged 60 or older, should provide some answers by 2020. (Interested in participating? Visit www.cosmostrial.org or call 800-633-6913.)

Until then, says Sesso, “we hope to fill in some of these research gaps with observational studies.”

Observational studies provide clues

Unlike a clinical trial, observational studies look at the risk of disease among people who do or don’t choose to take a multi on their own.

For example, the Nurses’ Health Study II has tracked more than 43,000 women since 1989. Those who took multivitamins were less likely to have precancerous colon polyps and less likely to be infertile because of ovulation problems.

“The challenge in looking at observational studies is that people who take multivitamins differ from those who don’t,” says Sesso. “While observational studies try their best to account for the differences—like smoking and exercise—they can’t adjust for differences they don’t know about.”photodune-200423-mix-of-vitamins-for-WC

Then there’s the question of what people take. “We don’t know if all multivitamin formulations have similar effects, or whether particular combinations of vitamins and minerals are better than others,” says Sesso.

Could multis be harmful?

A 2011 observational study of Iowa women rattled some people when it found that multi takers were slightly more likely to die than non-multi takers. But the result appears to be a fluke. Other observational studies and clinical trials don’t find a higher risk of dying among those taking a multi.

“There doesn’t appear to be any harm from taking ordinary big-brand multivitamins,” says Sesso. “But whether they can prevent disease remains a work in progress.”

Skip the specialized formulations that add herbs or other botanicals, says Sesso. “We don’t really know how these ingredients interact and what their long-term effects are.”

Sources: JAMA 308: 1871, 2012; Ophthalmology 121: 525, 2014; JAMA 308: 1751, 2012; Ann. Intern. Med. 159: 806, 2013; Br. J. Cancer 110: 249, 2014; Fertil. Steril. 89: 668, 2008; Arch. Intern. Med. 171: 1625, 2011; Am. J. Epidemiol. 173: 906, 2011; Am. J. Clin. Nutr. 97: 437, 2013.

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8 Replies to “Can multivitamins protect you from cancer?”

    1. Harvard’s Howard Sesso would say that there’s evidence from a gold-standard type of study, a large randomized controlled trial, that men who take an ordinary multivitamin every day may have a modestly lower risk of developing cancer or cataracts. And there’s no demonstrable harm in taking a multivitamin.

  1. Why is this news now, when the most recent study listed in the Sources is from two years ago? And how is the lay person to evaluate the significance of a relative risk reduction without the context of the actual risk being reduced? Oh, wait; I’m female, so all bets are off anyway.

    1. The study was actually reported four years ago, but it’s still the largest and best-run study of its kind. The reduction in risk was modest but significant. See for yourself. Here’s a link to the full study: Multivitamins in the Prevention of Cancer in Men: The Physicians’ Health Study II Randomized Controlled Trial. Check out the graphs. The Harvard researchers are well aware of the lack of information about women. That’s why they’re launching a new trial called COSMOS to study the effect of multivitamins in women. Interested in joining the study? Here’s more information about participating in the COSMOS trial.

  2. Sigh…Centrum Silver? How often do supplements get slammed because quality and purity are not controlled for. There is a difference and I can’t even consider the validity of the research when such junk is used. Also, there is this underlining assumption that supplements are going to cure something. These kinds of studies just confused people about what is prudent supplementation to prevent micronutrient deficiencies or frank deficiencies. For those out there that think you can get what you need from food, nope. Not in today’s polluted, stressed out, overly processed culture. Please stop doing these stupid studies or reporting on them.

    1. Some of our readers believe that ordinary inexpensive multivitamins are worthless “junk” and some believe that fancier, more expensive multivitamins are superior. It’s a position companies selling the more expensive supplements like to promote.

      However, there’s not much hard evidence to support this distinction. Independent tests do not show that the “quality and purity” of products like Centrum Silver “are not controlled for.” The nutrients in these kinds of products have been used successfully in thousands of nutrition studies over the past 80 years or so.

      The Harvard researchers did not assume that the supplement they tested would “cure something.” They were surprised to discover when the experiment ended that the multi-takers had a lower rate of cancer and cataracts (but not of cardiovascular disease or cognitive decline) than the men assigned to a placebo. We don’t believe that it’s “stupid” to report the results of this study or “stupid” of the researchers to see if the same will hold true for women.

  3. David, I agree with Larry. Not all vitamins are created equal and I’m surprised that you would promote an inferior product like Centrum Silver. Take a look at the Landmark Study which was conducted by UC Berkeley. The results are astonishing when high quality “expensive” vitamins are used as opposed to the inexpensive ones. Those using inexpensive vitamins fared worse than people that used no supplements at all.

    1. First, there’s no evidence that Centrum is an inferior product. If you have documentation that it is, please provide it so that we analyze it. (We have no financial relationship with any supplement company.)

      Second, the Landmark Study was not conducted by UC Berkeley. It was conducted by the Shaklee Corporation, a supplement manufacturer, with input from a paid consultant who was also a professor at Berkeley.

      Third, the results were not astonishing and they did not demonstrate any superiority of “expensive” vitamins or any inferiority of “inexpensive” vitamins. The study compared apples with oranges.

      It randomly selected two groups from a nationally representative health survey. One group took a multivitamin (whether it was expensive or inexpensive was unknown), the other group didn’t take supplements. The study compared these two groups with a third group of long-time Shaklee customers who volunteered to be studied. That’s all you need to know to conclude that this study won’t tell you anything reliable. But it gets worse. The Shaklee group, which had been buying expensive supplements from Shaklee for more than 20 years, was also much wealthier, had much more education, was leaner, and had lower cholesterol levels. Plus, they took an average of 17 supplements every day! So they were probably different in lots of other ways that affected their health.

      So guess what? The Shaklee group had healthier levels of nutrients and other biomarkers in their blood than the other two groups. This could have been due to the 17 supplements, a better diet, or something else. But there’s no way to conclude that it was due to the “superiority” of the multivitamin they were taking compared with the “inferiority” of the multivitamin the other group was taking and the authors of study (mostly Shaklee employees) didn’t even try to draw that conclusion.

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