Soaring sales of supplements have scientists asking questions

Combining fortified foods and large doses of vitamin tablets could be too much of a good thing, cautions a group of scientists.

By Susan J. Landers — Posted June 19, 2006

Print  |   Email  |   Respond  |   Reprints  |   Like Facebook  |   Share Twitter  |   Tweet Linkedin

The millions of Americans who take a multivitamin and mineral pill each day aren't basing that decision on scientific evidence because there isn't any, according to a panel of nutritionists, biostatisticians and epidemiologists who met at the National Institutes of Health in mid-May to review the data on the safety and efficacy of such supplements for generally healthy people.

Plus, multivitamin users even might be causing themselves harm by unknowingly exceeding the upper safe limits of some vitamins, said the independent panel that gathered evidence from experts and members of the public for two days before compiling their findings in a report released May 17.

When all is said and done, according to the panel, there is little to support or reject widely held convictions that multivitamin tablets are important for good health.

They recommended that researchers mount vigorous studies to fill that void and that Congress expand the Food and Drug Administration's authority to tighten control over manufacturers.

"Half of American adults are taking multivitamins and minerals, and the bottom line is that we don't know for sure that they're benefiting from them. In fact, we're concerned that some people may be getting too much of certain nutrients," said panel Chair J. Michael McGinnis, MD, senior scholar with the Institute of Medicine.

Annual sales of supplements total about $23 billion, a substantial portion of which is spent on vitamins and minerals. Their increasing popularity often leads to confusion in physicians' offices over the pros and cons of their use by patients.

Although panelists were unable to shed much light on the use of multivitamins, they did provide a few recommendations for particular groups of patients. They advised that postmenopausal women take supplements of calcium and vitamin D for bone health; that antioxidants and zinc be considered for use by nonsmokers with early-stage, age-related macular degeneration and that women of childbearing age take daily folate to prevent neural tube defects in infants.

One problem in assessing health benefits arises because people who take vitamins are generally healthier than average to begin with, group members said. Consumers of vitamins often have healthier lifestyles and diets and a generally lower body mass index than nonconsumers. Use is also higher among women, the children of women who use vitamins, the elderly and those who have more education and higher incomes.

Ironically, the panel said, people least likely to take multivitamins are those who are more likely to have nutritional inadequacies and who stand to benefit the most.

Vitamin users are also in danger of inadvertently exceeding safe upper limits. So many foods are now fortified with vitamins and minerals that it is difficult to calculate just how much of a particular nutrient an individual is consuming, the panel reported. An estimated 65% of Americans used fortified foods or beverages last year.

The panel also examined available data on a few specific vitamins and minerals. They found that for beta carotene, for example, two large trials uncovered an increase in lung cancer among smokers and asbestos workers who took the vitamin but no preventive effect for a number of other cancers. Clinical trials testing vitamin E's protective value for cardiovascular disease found no decrease in death, although there was a decreased risk in prostate cancer among male smokers.

These findings may be part of a complicated story, noted Meir Stampfer, MD, DrPH, professor of epidemiology and nutrition at Harvard's School of Public Health, in testimony before the panel. Certain subsets of people, for example male smokers, may benefit from certain supplements, such as vitamin E, while others may not, he said.

It is particularly difficult to determine whether vitamins have any effect on cancer, he told the panel, because of the long time it takes for the disease to develop.

Irwin Rosenberg, MD, senior scientist and professor at the Jean Mayer Human Nutrition Research Center at Tufts University in Boston, decried the lack of a definition for multivitamins which differ in content and dose. "Good research requires good nomenclature, and that doesn't exist in vitamins," he said. For purposes of their review, the panel defined multivitamins and minerals as any supplement containing three or more vitamins and minerals.

The dietary supplement industry's trade association, the Council for Responsible Nutrition, took issue with some of the panel's findings. While agreeing with the recommendation that adverse events should be reported to the FDA, the group also pointed to the benefits of a daily multivitamin in promoting good health.

"For millions of Americans who struggle with diet and nutrition, a daily multivitamin provides a safe, affordable and reliable means of filling nutrition gaps and promoting overall good health," said CRN President and CEO Steven M. Mister.

Back to top


Finding the answers

A state-of-the-science report written by a panel of nutritionists, epidemiologists and others and convened by the National Institutes of Health made the following recommendations to fill the research gap on the connection between multivitamins and minerals and good health:

  • Elicit more accurate information from individuals to improve the quality of self-reported data on multivitamin and mineral use.
  • Build new multivitamin and mineral databases that detail the exact composition of supplements, update them on a continuous basis and assure their constant availability to the research community.
  • Determine the most-effective means to translate scientific information and improve communication on dietary supplements among consumers, health care professionals, industry, scientists and policy-makers.
  • Develop a strategy to support the study of possible interactions with nutrients or prescribed and over-the-counter medications.

Back to top

External links

Draft statement of the National Institutes of Health State-of-the-Science Panel on multivitamin/mineral use, May 15-17, in pdf (link)

Back to top



Read story

Confronting bias against obese patients

Medical educators are starting to raise awareness about how weight-related stigma can impair patient-physician communication and the treatment of obesity. Read story

Read story


American Medical News is ceasing publication after 55 years of serving physicians by keeping them informed of their rapidly changing profession. Read story

Read story

Policing medical practice employees after work

Doctors can try to regulate staff actions outside the office, but they must watch what they try to stamp out and how they do it. Read story

Read story

Diabetes prevention: Set on a course for lifestyle change

The YMCA's evidence-based program is helping prediabetic patients eat right, get active and lose weight. Read story

Read story

Medicaid's muddled preventive care picture

The health system reform law promises no-cost coverage of a lengthy list of screenings and other prevention services, but some beneficiaries still might miss out. Read story

Read story

How to get tax breaks for your medical practice

Federal, state and local governments offer doctors incentives because practices are recognized as economic engines. But physicians must know how and where to find them. Read story

Read story

Advance pay ACOs: A down payment on Medicare's future

Accountable care organizations that pay doctors up-front bring practice improvements, but it's unclear yet if program actuaries will see a return on investment. Read story

Read story

Physician liability: Your team, your legal risk

When health care team members drop the ball, it's often doctors who end up in court. How can physicians improve such care and avoid risks? Read story

  • Stay informed
  • Twitter
  • Facebook
  • RSS
  • LinkedIn