The daily multivitamin pill is no substitute for a good diet. But none of us is perfect when it comes to healthful eating. We may know all about the virtues of leafy green vegetables and whole grains, but convenience and cravings lead us astray. The multivitamin is partial protection from our lapses.
It's also an easy way to add surplus vitamins and minerals to our diets. Historically, nutrition focused on vitamin deficiencies that cause disease. But with fortification — the systemic addition of nutrients, chiefly vitamins, to the food supply — and no shortage of food, the focus changed to whether vitamins and minerals in amounts larger than we need might protect us against conditions like heart disease and cancer.
Studies go against vitamins
Some people scarf down megadoses, an approach most experts disagree with. The daily multivitamin is the cautious wager that some extra vitamins and minerals will pay off in better health even if deficiencies aren't a problem.
Lately, though, it's been looking like they might not, as high-profile studies have come to negative conclusions.
It's well established that a trio of B vitamins — B6, B12, and folate — lowers homocysteine, an amino acid that's a risk factor for heart attack, stroke, and dementia.
But results from a large randomized controlled trial published in the New England Journal of Medicine (NEJM) earlier this year showed that while the B vitamins lowered homocysteine levels, that didn't result in fewer heart attacks or other major cardiovascular events. A second disappointing study was published in NEJM. Despite their homocysteine-lowering prowess, B vitamins were no better than placebo at protecting people from cognitive decline.
Vitamin E hasn't been faring too well, either. In 2005 Johns Hopkins researchers found that large daily doses (400 IU and up) may increase mortality risk.
NIH shrugs its shoulders
The National Institutes of Health (NIH) convened a meeting on multivitamin and mineral supplements in May 2006. Experts listen to presentations by other experts for a couple of days, then issue a "state of the science" statement.
In this case, the statement was extremely cautious. Present evidence is "insufficient to recommend either for or against the use of multivitamin/multimineral supplements by the American public to prevent chronic disease," was the inconclusive conclusion.
Yes to a multivitamin
Dr. Walter Willett, chair of the Harvard School of Public Health's nutrition department, has suggested that taking a multivitamin daily is a form of nutritional insurance. He still says it's a good policy, despite the spate of negative study results.
Those results have come from randomized controlled trials, which are usually regarded as the gold standard. But there are problems with clinical trials, too. They're often fairly short, so a nutrient's long-term consequences may be missed.
There are also often questions about how applicable the results of clinical trials are because of the use of high risk individuals versus healthier folks. Multivitamins are already part of some official recommendations. The federal government's 2005 Dietary Guidelines suggest that people older than 50 take them as a way to ensure adequate vitamin B12 intake. And the Centers for Disease Control and Prevention advises all women of child-bearing age to take folic acid — and a multivitamin is also a good way to do that.
If you take a multivitamin, be sure to buy a major brand-name or store-brand product. When Consumers Union tested cut-rate products, it found that almost half didn't contain the listed amount of at least one nutrient.
September 2006 Update