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ATLANTA -- Despite fortification of the food supply with folic acid, serum folate levels have fallen en masse among women in recent years, researchers said.
ATLANTA, Jan. 5 -- Despite fortification of the food supply with folic acid, serum folate levels have dropped en masse among women in recent years, researchers said.
Median serum folate concentrations among women of childbearing age decreased 16% from 1999--the year after fortification started--to 2004, said Sheree L. Boulet, Dr.P.H., of the National Center on Birth Defects and Developmental Disabilities, and colleagues.
Red blood cell folate concentrations also decreased 8% in the same period, they wrote in the Jan. 5 issue of Morbidity and Mortality Weekly Report, a CDC publication.
Folic acid, the synthetic form of folate, is added to enriched cereal-grain products to help prevent neural tube birth defects (NTD) such as spinal bifida or anencephaly.
In an accompanying note, MMWR's editors suggested that the results do not reflect that folic acid fortification does not work .A previous study found that serum folate levels increased from a mean of 4.8 ng/mL before fortification during 1988 to 1994 to about 13.0 ng/mL in 1999 to 2000 after it started, with similar increases in red blood cell folate concentrations.
The editors suggested that he finding reflects other changes that have occurred in the American population.
"More likely explanations include 1) changes over time in the proportion of women taking supplements containing folic acid, 2) decreased consumption of foods rich in natural folates or foods fortified with folic acid (i.e., enriched cereal-grain products), 3) variations in the amounts of folic acid added to enriched grain products since fortification was mandated, and 4) increases in risk factors associated with lower folate concentrations such as obesity."
The researchers compared National Health and Nutrition Examination Survey (NHANES) data for the periods 1999 to 2000, 2001 to 2002, and 2003 to 2004. Each included a nationally representative sample of the civilian, noninstitutionalized population. Members of these groups were individually interviewed and underwent a physical examination including blood sample collection.
They found that the median serum folate concentration among women ages 15 to 44 were:
Overall, this represented a significant decline (P
Future studies should link these findings to data from the National Birth Defects Prevention Network to see if the declines in folate levels have affected neural tube birth defect prevalence, they added.
The CDC recommends that all women of childbearing age capable of becoming pregnant should consume 400 ?g of folic acid daily. Since fortification is not expected to provide the full daily requirement, women should consume a diet containing folate-rich or -fortified foods as well as dietary supplements, according to the CDC.