Aug. 4, 1997 BALTIMORE--Studies show that supplementing a mother's diet with folic acid before and during pregnancy can reduce incidences of neural tube birth defects in children. But researchers at the University of Maryland School of Pharmacy, found poor folic acid dissolution in six prenatal prescription multivitamins they tested, raising questions as to whether or not absorption by the body is complete.
Stephen Hoag, Ph.D., assistant professor at the UM School of Pharmacy, says tests of nine prenatal prescription multivitamins found six products did not release at least 75 percent of the amount of folic acid listed on their labels in one hour, an industry standard set in 1995.
The report, written by Hoag and co-author Ralph Shangraw, Ph.D., professor emeritus with the UM School of Pharmacy, and Hanu Ramachandruni, M.S., a graduate student in the pharmacy school, was published in the July-August issue of the Journal of the American Pharmaceutical Association.
"Typically vitamins, including folic acid, are more readily absorbed in the upper gastrointestinal tract, just beyond the stomach," says Hoag. "Not meeting the standard of dissolving within an hour highlights a potential problem with these products. The amount of folic acid available for optimal absorption in the body could be inadequate."
While dissolution of a substance does not guarantee absorption, the researchers say it is necessary for absorption to occur. Many of the products Hoag tested missed the minimum standard by a wide margin, two released less than 25 percent of the labeled quantity.
Hoag and Shangraw say they will not name the products studied because federal regulations and standards for nutritional supplements are changing and some manufacturers have improved their products to insure proper dissolution before this research was published. The standards for folic acid dissolution are developed by the United States Pharmacopeial Convention. Nutritional products meeting these standards can label their products USP.
"Folic acid is caught in evolving regulatory policies and is regulated by the FDA as a food, not a drug," says Shangraw. "Only products that bear a health claim stating that increased folic acid intake before conception and during early pregnancy reduces the risk of having a baby with neural tube defects, are required to meet a USP folic acid dissolution standard. Although the products tested contained 1 mg of folic acid, were clearly labeled prenatal vitamins and sold by prescription only, they technically did not have to meet dissolution standards. It seems reasonable that they should," says Shangraw.
"For drugs it is standard to analyze blood levels to make sure the substance is absorbed. You must substantiate purity, safety and efficacy with data in a drug application to the FDA. But because nutritional supplements are regulated as a food, the standards are different," says Hoag.
"Scientifically we know about how drugs are absorbed by the body, but there has been very little research into bioavailability from vitamin tablets or capsules," says Shangraw.
Hoag and Shangraw say people should not stop taking their vitamins. "Vitamins should preferably be taken with food and plenty of fluids. Any amount absorbed is beneficial, and no one is sure what amount of folic acid is needed to reduce neural tube defects," says Shangraw.
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