Don’t Jump to Conclusions on Multivitamin Heart-Attack Protection
I f you saw the headlines about a recent study—“Multivitamins Shield from Heart Attack,” “Multivitamins Keep Heart Attack at Bay”—you may be tempted to join the estimated 75 million Americans who take a daily multivitamin. But not so fast. Even the lead researcher on the new study, Susanne Rautiainen, MSc, of Sweden’s Karolinska Institute, cautions, “The question of whether multivitamins are good for you still remains.”
Evaluating any health benefts of multivitamins turns out to be a sort of chicken-and-egg problem: Are people healthier because they take multivita- mins? Or is it simply that people with more important healthy habits—exer- cising, eating right, not smoking—also happen to take multivitamins?
It’s true that Rautiainen and col- leagues recently reported that women taking multivitamins were 27% less likely to suffer heart attacks than non-supplement users. The research- ers studied 31,671 women with no history of heart disease, ages 49 to 83; about 60% took some sort of dietary supplement. Over a little more than 10 years of followup, 932 of the women suffered heart attacks.
Taking a multivitamin plus other supplements was associated with a 30% lower heart-attack risk, but other sup- plements alone were not linked to any risk reduction. Taking multivitamins for 10 or more years was associated with a 41% lower likelihood of heart attack.
Results were less positive, however, among another 2,262 women who did have cardiovascular disease at the study’s start; 269 of these women had heart attacks during the followup period. In this group, there was no statistically signifcant difference in heart-attack incidence associated with multivitamin use.
In an interview following the study’s publication in the American Journal of Clinical Nutrition, Rautiainen warned that the fndings don’t prove multivita- mins protect against heart attacks. For one thing, this was an observational study, not a randomized trial, so the re- search was not designed to show cause and effect.
Moreover, she said, “It is very im- portant to keep in mind that multivita- min users tend be ‘healthier’ in general. They usually smoke less, are more physi- cally active and have a healthier diet. Even if we have controlled for many of those factors that are associated with a healthy behavior, we cannot exclude the possibility that we might measure a healthy lifestyle via multivitamin use.”
A lthough multivitamin use is wide- spread, Rautiainen and colleagues noted, little data is available on the relationship, if any, between the supple- ments and incidence of coronary heart disease. They cited only one randomized trial of low-dose multivitamins and heart disease, which showed no signifcant benefits.
Results from observational studies have been mixed. One American study found that use of multivitamins plus antioxi- dant vitamin supplements was associated with a 25% lower risk of death from heart disease. A Dutch prospective cohort study saw a 51% lower incidence of heart attacks among multivitamin users.
In 2009, however, the largest study ever of multivita- min use among older women found that the pills made no signifcant difference in the risk of heart disease. Researchers analyzed data on 161,808 postmenopausal women partici- pating in four parts of the Women’s Health Initiative (WHI), a little more than 40% of whom used multivitamins. The study also found no protective beneft from the supplements against cancer or in overall mortality. Not even women who took multivitamins for a long time showed any difference in risk compared to non-multivitamin users or those who took the pills for just a short period.
Multivitamin use may even have a downside, according to surprising results reported last year by another team of Swed- ish scientists. They followed more than 35,000 women, ages 49 to 83 at baseline, over an average of 10 years, during which 974 participants were diagnosed with breast cancer. After ad- justing for known risk factors, multivitamin users—a little ov a quarter of the women—were 19% more likely to develop breast cancer. While there’s no way to know if the supplemen actually contributed to the cancers, researchers said such an effect is “biologically plausible” and further investigation is warranted. In any case, they added, “If you eat a healthy and varied diet, there is no need to take multivitamins.”
|Do You Need a Multivitamin?|
Some people with special nutritional issues can probably beneft from a daily multivitamin. For most people eating a healthy, varied diet, the need for a multivitamin as “nutritional insurance” is less clear. It’s certainly true that you’re better off getting your nutrients from food than pills. Still, even with a healthy diet you may be falling short on specifc nutrients. Some older people have a diminished capacity to absorb vitamin B12 from food. Especially in northern latitudes in winter, it can be diffcult to get adequate vitamin D from sunlight and your diet; most multivitamins, however, don’t supply as much vitamin D as experts recommend. If you have these concerns, it might be best to talk with your physician about specifc supplements you may need, rather than relying on an all-purpose multivitamin. American Journal of Clinical Nutrition, October 2010; abstract at <http://www.ajcn.org/cgi/content/abstract/92/5/1251>