Panel slams lack of science behind vitamin and mineral supplementation

A consensus panel convened by the National Institutes of Health (NIH) has cited a dearth of information about dietary supplements and their health effects in calling for study and regulation of these products by the Food and Drug Administration (FDA). The independent committee, which met for three days this Spring at the NIH campus outside Washington, DC, recommended that Congress expand FDA's authority to ensure quality in the production of supplements, require manufacturers to disclose reported adverse events, and require information on product labels that will help consumers report such events.

The panel's charge was specific: Look at the evidence that multivitamins are efficacious in preventing chronic disease.

"Most of the public assumes that the components of multivitamin and mineral supplements are safe, because many of the ingredients are found in everyday foods and the products are available over the counter," according to the joint statement issued by the panel's 13 health experts. The group included two pediatricians.

The percentage of people in the US using multivitamin and mineral supplements has doubled in recent years, to 52%, according to data from the National Health and Nutrition Examination Survey from the National Center for Health Statistics. That percentage includes almost one half of preschoolers, who take a multivitamin with or without iron. Use of supplement products is higher, said the panel report, among women and the children of women who use supplements.

What about the children?

Panelist Nigel Paneth, MD, MPH, professor of epidemiology and pediatrics at Michigan State University, noted that supplementation in children is usually undertaken to prevent nutritional deficiencies and that the panel's investigation excluded most diseases of children. But many of the issues the report raises do apply to supplementation in children.

For example, said the panel in its statement, it's impossible to even know what is in many supplement products.

"There are thousands of product labels, vast differences in the amounts of vitamins and minerals delivered by various products, and major changes within the same product over time and across batches."

Furthermore, consumers often can't identify the products they use.

The experts called for establishing, and regularly updating, new databases that list the exact composition of supplement products.

Several studies also indicate that, ironically, people who take multivitamins and minerals are often health-conscious and therefore more likely eat the types of foods that give them higher levels of micronutrients. That situation also pertains to children whose health-conscious parents make menu decisions for them.

At the same time, the movement to fortify foods with micronutrients makes it even harder to know how much supplementation people receive.

Adverse events, safety addressed

The panel statement pointed out that reports of adverse events with multivitamins and minerals appear with "some frequency" in the records of the American Association of Poison Control Centers and in FDA Medwatch reports.

Patsy Brannon, PhD, RD, professor of nutrition at Cornell University, said that, among supplement uses that raise concern over exceeding upper limits of safety, iron in children is prominent.

The report calls for, among other research, randomized, controlled clinical trials on the impact of individual supplements to test their safety and their efficacy in preventing chronic disease. It also calls for research on possible harmful interactions among multivitamins, mineral supplements, nutrients in foods, prescription medications, and over-the-counter preparations.

The report noted, in particular, that some observational studies, such as ones suggesting that beta carotene might protect against cancer, were misleading.

The panel did carefully emphasize that it endorsed the current Centers for Disease Control and Prevention recommendation that folic acid be taken by women of childbearing age to prevent neural tube defects. Members called the research behind that initiative one of the great triumphs in the study of nutrients.

The panel's draft statement is at http://consensus.nih.gov/.