For some people, multivitamins are a safety net, a way to fill in the nutritional chinks—but do they actually help?
We asked four Tufts nutritionists to sit down for a roundtable discussion about the science of multivitamins and to answer a simple question: Should healthy adults take them?
The participants were:
Jeffrey Blumberg, Friedman School professor and director of the Antioxidants Research Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA)
Johanna Dwyer, professor at Tufts School of Medicine, director of the Frances Stern Nutrition Center and a senior nutrition scientist for the Office of Dietary Supplements at the National Institutes of Health
Alice H. Lichtenstein, Gershoff Professor of Nutrition Science and Policy at the Friedman School, professor at Tufts School of Medicine and director of the Cardiovascular Nutrition Laboratory at the HNRCA
Joel Mason, professor at the Friedman School and Tufts School of Medicine and director of the Vitamins and Carcinogenesis Laboratory at the HNRCA
Tufts Now: I am a fairly healthy adult, and I think I eat a slightly better-than-average diet. My doctor says I should take a multivitamin—she recommends it for all women my age. Should I take one?
Blumberg: I feel there is no harm in taking a multivitamin, and doing so will help fill in the gaps. More than half the American population isn’t consuming the amounts of fruits, vegetables and whole grains that we recommend to help them meet their needs for vitamins and minerals.
Lichtenstein: Your physician’s recommendation is not consistent with current clinical guidelines. There was a very extensive systematic review sponsored by the federal government that was done by the Johns Hopkins Evidence-Based Practice Center that showed no benefit to the general population from a multivitamin.
It may be useful in certain select groups, but we know that in the U.S., those individuals who need a multivitamin most—those who are nutrient-insufficient—are less likely to use supplements anyway. We’re not even sure whether falling a little bit below the Recommended Dietary Allowances (RDAs) is causing a problem, because there don’t seem to be clinical manifestations in general.
One of the problems is that when you put an emphasis on something like whether people should take a multivitamin, you shift the focus off what is really important: that they are eating too many calories, too much saturated fat and trans fat, too much sodium, not enough fiber, and they are not exercising enough. There is no quick fix. You can’t just pop a pill and make everything better.
Blumberg: I agree. If you want to take a multivitamin because you love to eat at fast-food restaurants 10 times a week, and you hate fruit and vegetables and you think you can compensate for that, my answer is no, you can’t. Multivitamins are supplements, not substitutes for a healthy diet.
And I agree that the people who need a multivitamin most are the ones who aren’t taking them. Who is taking a multivitamin? The more affluent, the more highly educated, the people who are actually eating better diets, who exercise, don’t smoke. The people who really need to be listening to their doctor’s advice to take a multivitamin are not.
But I don’t agree with the converse: that people who need them the least don’t need them at all, because they are not meeting their RDAs either. Maybe some of the RDAs are not perfect, but they are a goal that reflects the current consensus, and we know that most people aren’t meeting it.
Dwyer: Speaking for myself, I don’t think that a multivitamin is going to cause any particular good, nor do I think it is going to cause any particular harm. It’s a personal choice. It’s like whether people should be avoiding every animal food or everything that has added sugar. A lot of these blanket statements about absolutely consuming or not consuming foods or multivitamins are oversimplified, inconsequential, yuppie-related food faddism.
So what you are saying is, it’s up to me; it probably won’t hurt, but at the same time why are we arguing about this when there are bigger problems?
When I asked a few people why they take multivitamins, they said things like, “I’m a little anemic, so I need the iron,” or “That’s how I get my vitamin D.” It seems to be one-stop shopping for a variety of concerns.
Mason: I think this mindless approach that many Americans (and for that matter many American physicians) take—that it might help, and it can’t hurt—is not necessarily the most cogent one. Now, it might be that as a young woman, you aren’t getting enough vitamin D and calcium. The multivitamin might not be the right approach, because most multivitamins have a trivial amount of calcium. If you really think carefully about what you as an individual need, most often you are going to end up with a more intelligent strategy.
Lichtenstein: If your physician finds that you need more calcium, I would ask, have you tried low-fat Greek yogurt? Do you think there is a way of increasing your dairy intake? There are so many food-based ways of getting your nutrients.
Dwyer: Years ago I was studying vegetarians, and some of them told me they took a vitamin supplement because they weren’t getting enough calcium and iron. If you looked at the vitamins they were taking, they were indeed vitamins, but the calcium and iron they needed were minerals.
Indiscriminate vitamin use is sort of like the use of holy water in the Middle Ages: People thought if you sprinkled it on things, it would ward off all evil. People who take supplements would probably be offended by that, but sometimes if you look at their reasons, they are not more sophisticated than beliefs in the Middle Ages.
Let’s talk about the risks. What about the 2011 Iowa Women’s Health Study, the observational study that found there was an increased risk of death in women who took multivitamins?
Dwyer: To say that multivitamins are causing mortality—I really believe that is a big stretch, and I don’t think that particular paper is in line with the rest of the literature. Most of the studies that say things like that are not controlling for the confounders, such as smoking, obesity, preexisting illness, etc. Sadly, you can’t control for all of the confounders in an observational study.
Is that why we don’t know definitely whether multivitamins are good or bad, because they are just really hard to study?
Dwyer: It’s extremely expensive to study them well in large randomized clinical trials that last for many years, especially with hard end points such as mortality or heart attacks. There have been several very good, randomized studies that did not show any adverse effects from multivitamins.
Blumberg: There are now several meta-analyses of multivitamins and mortality, and they show no benefit, no harm.
The Physicians Health Study II recently tested a complete multivitamin in 15,000 men and reported a modest reduction in total incidences of cancer. I don’t wish to overstate the benefit found here, but it was a large, long-term and well-controlled study. Not surprisingly, many have pointed out the complexities and limitations associated with this and similar studies. Yet if investing millions of dollars in a randomized clinical trial like this—the “gold-standard” for medicine—is still insufficient to provide convincing evidence of benefit, then we need to find new and practical approaches.
Lichtenstein: In talking about potential harm, the other thing we have to remember is that a tremendous amount of the foods we consume are fortified. If you are consuming a bowl of breakfast cereal that has 100 percent of the RDA, if you are getting orange juice that has calcium and vitamin D added to it, or a powdered beverage mix that has vitamin C, you already may be getting the equivalent of a multivitamin pill.
I think we are just beginning to learn the effects of overconsumption of nutrients. We really don’t know that accurately what people are consuming. We don’t have a standardized system in the United States for monitoring it. The whole reason a new category—the tolerable upper intake levels (ULs)—was introduced was to address this. I think we need to be a little cautious.
Blumberg: I don’t see anything in the Centers for Disease Control’s Morbidity and Mortality weekly report to suggest that there is an epidemic of people showing up in emergency rooms with vitamin toxicities. When we look at the RDAs versus the ULs for most nutrients, we are talking about five to 10 times higher than that. So there is a pretty big range for most nutrients before you run into harm. Vitamin A [which has been associated with bone loss] is an exception.
Lichtenstein: I agree. I’m not saying that there is harm. I guess the question I would ask somebody is: Are you already getting the equivalent of a multivitamin supplement in your diet because of your breakfast cereal, because you’re drinking multiples of these vitamin waters, because of fortified OJ?
Mason: This kind of goes back to one of the buzzwords these days: personalized medicine. I think trying to make recommendations for an entire population versus recommendations for a particular individual puts us at loggerheads.
Blumberg: One meaningful step toward personalized nutrition is if your doctor would just give you a little dietary assessment.
Lichtenstein [applauding]: Yay!
Mason: I bet you could design a five-item questionnaire that would effectively and validly define those people who could potentially benefit from a multivitamin versus those who wouldn’t. While you’re waiting in the doctor’s waiting room, instead of reading a six-month-old issue of Cosmopolitan, you could just as soon answer the five questions, and the physician assistant would say, “You know what? You fall into a category that would benefit from a multivitamin.”
Lichtenstein: Or the PA would say, “We need to probe more.”
This article first appeared in the Summer 2013 issue of Tufts Nutrition magazine.
Julie Flaherty can be reached at firstname.lastname@example.org.