From MedPage today:
Daily Multivitamins: A Ubiquitous Article of Faith
By Katrina Woznicki, MedPage Today Staff Writer
Reviewed by Rubeen K. Israni, M.D., Fellow, Renal-Electrolyte and Hypertension Division, University of Pennsylvania School of Medicine
WASHINGTON, Sept. 6-Every day, President George Bush practices faith-based preventive medicine when he reaches for his daily multivitamin.
Like millions of his fellow Americans, Bush assumes that the multivitamin bestows vague generalized beneficial properties, although he and others would be hard-pressed to cite specifics. Indeed, there are scant solid data on whether multivitamins offer any benefit at all to healthy adults.
Popping the daily multivitamin is as routine as the morning cup of coffee. Multivitamins are cheap and easy to access, giving people the quick gratification that they've taken a small step towards protecting their well-being.
Yet the goodness is an article of faith. A multivitamin is not an insurance policy against disease or a guarantee of longevity. It may, in fact, be little more than just another substance for the body to excrete, at least for a healthy adult.
Much of the current literature on vitamins focuses on testing whether a specific nutrient has any effect on a particular condition. Some evidence suggests a regular multivitamin may offer some benefit to subgroups of patients who have chronic conditions, and there's solid evidence that the folate in a multivitamin benefits women and their fetuses during pregnancy.
But for healthy adults, the jury is out. Whether a daily multivitamin provides any clinical benefit to the average healthy American depends on whom you ask.
"There's no evidence, no hard evidence that in the nutritionally replete, the person who consumes some fruits and vegetables every day, benefits," said Thomas Barringer, M.D., medical director of the center for cardiovascular health at Carolinas Medical Center in Charlotte, N.C. "I don't know why doctors recommend them. But it's very time-consuming trying to talk someone out of doing something that's pretty innocuous."
There are no randomized, double-blinded, controlled studies comparing a multivitamin with a placebo in healthy individuals to determine whether there's any tangible health benefit. Such a study would be costly and time-consuming. Experts on both sides of the issue agree on this point.
Where experts begin to disagree is whether the kind of evidence that currently exists on vitamins show any clinical benefit. The U.S. Preventive Services Task Force doesn't seem to think so.
In the July 1, 2003 issue of Annals of Internal Medicine, the task force said that "the best studies suggested no clear benefit of taking vitamins" and there was "insufficient scientific evidence to recommend vitamin supplements as a way to prevent cancer or heart disease." Their conclusions were based on a review of the literature.
The benefits of vitamin supplementation for the general population, said Janet Allen, Ph.D., R.N., vice chair of the task force, "remain uncertain."
But the task force noted that taking vitamins according to the recommended daily allowances "does not cause harm."
The American Academy of Family Physicians echoes the task force's sentiment that there's a lack of proof multivitamins provide any clinical benefits to average healthy adults. But the AAFP leaves the door open for family physicians to make their own recommendations.
"We allow family physicians to make decisions based on each patients' interest and needs," said Jim King, M.D., a member of AAFP's board of directors who is in private-practice in Selmer, Tenn. "There's really no proof out there that if you're a healthy person eating a reasonably healthy diet that a multivitamin is going to do anything. Most people get the amount of vitamins they need and don't realize they do get it."
This is another point where experts disagree. The modern fast-food diet consumed by countless Americans indicates that more persons are falling short of their recommended daily allowances of vitamins and minerals, said Jeffrey Blumberg, Ph.D., a professor of nutrition at Tufts University in Boston and director of the Antioxidants Research Laboratory
"Most health care providers aren't doing a lot of primary care prevention," Dr. Blumberg said. "We could reach the people who are not taking them if physicians were more assertive about recommending them."
Dr. Blumberg acknowledged that much of the data on vitamins is only observational.
"Most of them (physicians and physician groups) want the unequivocal evidence from randomized placebo-controlled studies, and we don't have that and those studies haven't been done," he said.
Andrew Shao, Ph.D., vice president of scientific and regulatory affairs at the Council for Responsible Nutrition, a Washington, D.C.-based trade association group, said physicians won't get the clear-cut answers on vitamins like they do with studies on drugs. The benefits of vitamins aren't always immediately obvious, he said.
"If people are taking a multivitamin and they're expecting to see some specific result in a short period of time, they are probably going to be disappointed," Dr. Shao said. "It's not a drug and it's not intended to be a drug. That doesn't diminish the importance of taking a multivitamin."
While the data are missing for the average healthy adult, there are data on vitamins and certain subgroups and that too, is mixed.
For example, studies have begun to chip away at the assertion that a multivitamin helps protect the elderly from infection.
A study in the Aug. 6 issue of the British Medical Journal found multivitamins failed to protect elderly patients from infection. The randomized, double-blind, placebo-controlled trial of 910 men and women, ages 65 and older found no significant differences between the two groups and the number of times they visited a physician for infection.
Four months earlier in another issue of BMJ, British researchers led by Alia El-Kadiki, a researcher at Royal Hallamshire Hospital in Sheffield, England, conducted a meta-analysis of the literature and concluded there was not enough evidence to recommend that the elderly take multivitamins to ward off infection.
"The evidence for routine use of multivitamin and mineral supplements to reduce infections in elderly people is weak and conflicting," they wrote.
Still, the door remains open on multivitamins' potential benefit for other population subgroups. Evidence from the Nurses' Health Study suggests a possible benefit to taking a multivitamin.
Reporting in the October 1998 issue of Annals of Internal Medicine, Harvard researchers reported that "long-term use of multivitamins may substantially reduce the risk for colon cancer."
Six years later, another study on women also from Harvard found taking a multivitamin reduced viral loads for HIV-infected women who were pregnant.
"Multivitamin supplements delay the progression of HIV," researchers wrote in a July 2004 issue of The New England Journal of Medicine.
There may be benefits for diabetics, too. Dr. Barringer's study, in a March 2003 issue of Annals of Internal Medicine, found a type 2 diabetes patients who took a daily multivitamin had a significantly lower rate of infection compared with those who took a placebo (17% vs. 93%, P<0.001).
The U.S. Preventive Services Task Force did not review studies that looked at whether vitamins may benefit people with nutritional deficiencies, pregnant and lactating women, children, the elderly, and people with chronic conditions.
"Vitamins may be more appropriate for these groups," the task force said.
Most physicians will agree that in the end, a daily multivitamin isn't going to hurt. But patients should be aware a multivitamin doesn't come with any promises either and that a pill isn't a substitute for a healthy diet.
"It's hard to tease out the exact benefit of a multivitamin," said Dr. Blumberg. "But it's a simple, convenient, very safe and proactive thing to do."