Multivitamins: Should you buy this insurance?

Studies have raised doubts about vitamins, but the multivitamin pill is still a good idea.

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. By definition, vitamins are organic (carbon-based) compounds needed in only small amounts. Minerals serve a similar purpose, but are inorganic. Historically, nutrition focused on vitamin deficiencies that cause disease. But with fortification — the addition of nutrients, chiefly vitamins, to the food supply — and no shortage of food, the focus changed to whether vitamins and minerals in amounts beyond our basic needs might protect us against conditions like heart disease and cancer.

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. The logical supposition: Having an ample supply of those Bs coursing through your veins (and arteries) could improve your chances of avoiding cardiovascular disease and cognitive decline.

But results from a large randomized controlled trial published in the New England Journal of Medicine (NEJM) in April 2006 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 in June 2006. 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. Johns Hopkins researchers dubbed 2005 the annus horribilis for vitamin E because of all the disappointing studies, chief among them their meta-analysis that found that large daily doses (400 IU and up) increased mortality risk.

The National Institutes of Health convened a meeting on multivitamin and mineral supplements in May 2006. The resulting 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. The experts noted that the heaviest users of vitamin and mineral supplements are Americans who probably need them the least: People who are well-educated, have higher incomes, exercise, and already have healthy diets.

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. For example, Dr. Willett says that beta carotene didn’t look like it was having any effect on cognition at the 12-year mark in Harvard’s Physicians’ Health Study, but at 18 years, benefits were detected.

There are also often questions about how applicable the results of clinical trials are. Some of the negative findings have come from studies that enrolled people who had vascular disease or diabetes. But how relevant are the findings to healthier folks? With the B vitamin research, it’s the reverse: The patients in those studies had homocysteine levels that were normal or just slightly elevated, so the results may not apply to people with higher levels.

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 — because doing so lowers the risk of birth defects. That leaves men age 50 and under as the only adult group not covered.

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.
 

For more information on vitamins and minerals in your diet, order our special health report Vitamins and Minerals: What you need to know, available at www.health.harvard.edu/VM.