Pregnant Women Advised Not to Use Multivitamins

Pregnant women should avoid vitamin and mineral supplements, except iron, and get the extra nutrients they need from a balanced diet, a National Academy of Sciences committee recommended today in a report that is sure to surprise obstetricians.

Multiple-vitamin supplements and iron tablets are commonly prescribed to women throughout pregnancy to ensure the proper development of the fetus. In addition, recent research has indicated that folic acid supplements might help prevent birth defects involving the spinal cord, such as spina bifida.

But the 11-member committee of medical and nutritional experts from the Institute of Medicine suggested that the fetus may suffer if vitamin supplementation replaces a well-balanced diet. Moreover, the committee concluded that more research is needed before widespread supplementation of folic acid can be advised to prevent spinal-cord defects, called neural tube defects.

The report encouraged health-care practitioners to identify special problems that might affect a pregnant woman’s nutritional needs and to counsel women on how to improve their diets. It is believed that this practice can eliminate the need for widely distributed prenatal multivitamin supplements. Supplementation, the committee said, should be a final intervention.

“There is considerable variation in nutrient requirements among individuals,” the report added. Food, the committee said, is the “normal vehicle for delivering nutrients and nutrient supplementation (is) an intervention (that should be) based on evidence of benefit as well as lack of harmful effects.”

The committee expressed concern that vitamin supplements might inhibit absorption of various minerals because the nutrients can interact in adverse ways. With normal food intake, nutrients are generally not consumed in such large concentrations at any one time as to interact or overwhelm each other.

But taken as a supplement, iron, for example, can inhibit the absorption of zinc, and zinc can affect the way the body handles copper, the committee said. And Vitamin A, or retinol, supplements can cause abnormal fetal development when prescribed during the first three months of pregnancy.

American College of Obstetricians and Gynecologists’ guidelines also discourage routine vitamin supplementation during pregnancy with the exception of iron and folic acid supplements, said Kate Ruddon, spokeswoman for the Washington-based group.

“Most women have an adequate diet that can meet the nutritional requirements of pregnancy,” Ruddon said. “However, if the physician suspects that a woman’s diet is inadequate, then he or she can recommend a multivitamin to make up the difference.”

For this reason, many doctors do prescribe multivitamins, experts said.

Ruddon said the College of Obstetricians and Gynecologists does not agree with the National Academy of Sciences recommendations on folic acid.

“The only thing we have contention with at this point is the folic acid,” Ruddon said. “The college has been considering nutrition recommendations for a long time, and we felt that folic acid isn’t one of the things a woman would get a lot of in her diet.”

Some research has demonstrated that women given folic acid supplements at the time of conception are less likely to give birth to a child with neural tube defects, but other studies have failed to confirm the relationship.

The academy committee concluded, however, that there is insufficient evidence on birth defects to recommend general use of multivitamin supplements, including folic acid, by all women of childbearing age.

But many medical experts fear that most pregnant women do not get adequate nutrition through food alone and may find it difficult to change their diets, said JoAnn Hattner, a clinical nutritionist at Stanford University Medical Center. Hattner said that individual nutrition counseling must be included as part of prenatal care if vitamin supplements are discontinued.

“I would agree that food is the best source of nutrients,” Hattner said. “It is the safest and most intelligent way, since trace elements are contained in food, too. But I would hate to assume that all pregnant women out there know how to eat a well-balanced diet for pregnancy.”

Other experts defended the use of vitamin supplements in pregnancy as safe and the most effective way to ensure proper nutrition.

“Prenatal supplements have been an accepted practice in the medical community for years,” said Linda Weinberg, a registered dietitian with the Vitamin Nutrition Information Service, a vitamin industry organization. “There have never been any adverse effects. It’s just a way to ensure that the mother gets what she needs, and now research says it may even prevent birth defects.”

It is unrealistic to expect women, who often have poor diets before pregnancy and may not receive prenatal care, to eat foods that supply all essential nutrients such as folic acid, said Dr. Judith Reichman, an obstetrician-gynecologist at Cedars-Sinai Medical Center in Los Angeles. Reichman defended multivitamin supplements as a safe form of nutritional insurance.

“If the academy thinks that all pregnant women in the United States are going to have optimal diets and see dietitians in order to get these optimal diets, they just aren’t thinking realistically,” she said. “I don’t think a vitamin pill a day is going to hurt anyone--we’re not giving megadoses.”

The panel did, however, recommend that pregnant women take a supplement of 30 milligrams of ferrous iron daily--the recommended dietary allowance--because women of childbearing age often begin pregnancy with a level of iron too low to meet the demands of the growing fetus.

The committee also recommended that healthy pregnant women gain more weight. Underweight women will now be advised to gain between 28 and 40 pounds. Overweight women, said the report, should try to gain no more than 15 to 25 pounds. Pregnant women of normal weight should follow their physician’s advice.

The report is the first update of the panel’s guidelines for prenatal care in 20 years. None of the recommendations are intended for women who have special health circumstances, such as those carrying more than one fetus, complete vegetarians, smokers or women who use alcohol or drugs, the panel said. Those women require individualized recommendations from their physicians, it said.

NUTRITION RECOMMENDATIONS

Recommendations of a National Academy of Sciences report on nutrition during pregnancy:

Eat a well-balanced diet rather than relying on vitamin supplements.

Eat plenty of fruit, green leafy vegetables, whole grains and legumes to meet the need for folic acid.

Take a 30-milligram iron supplement daily.

Underweight women should gain between 28 and 40 pounds. Overweight women should try to gain no more than 15 to 25 pounds.

Avoid taking special protein powders or formulated high-protein beverages.

Source: National Academy of Sciences