Healthnotes Newswire (June 21, 2001)—The government-mandated addition of folic acid to enriched grain products in the United States, which began in 1998, has led to a significant decrease in the prevalence of neural tube defects (NTDs), according to a study published in this week’s Journal of the American Medical Association (JAMA).1 While this decrease is good news for future parents, many doctors and scientists believe that a higher level of folic acid fortification could reduce NTD incidence even more.
Using birth certificate data for live births in the U.S., the authors compared the incidence of neural tube defects such as hydrocephalus (blocked drainage of fluid surrounding the brain), spina bifida (incomplete closure of the spinal column), and anencephaly (absence of most of the brain and spinal cord) before folic acid fortification (October 1995 through December 1996) to their incidence after mandatory fortification (October 1998 through December 1999).
The researchers found that fortification of grains with folic acid led to a 19% decline in the overall prevalence of NTDs compared to the pre-fortification period. The incidence of spina bifida alone decreased by 23%.
In an editorial accompanying the new study, Drs. James Mills and Lucinda England of the National Institute of Child Health and Human Development in Bethesda, Maryland, declare, “This exciting news clearly validates the U.S. government’s decision to intervene on a massive scale to prevent these devastating birth defects.”2 The consequences of neural tube defects range from mild or no disability (as in successfully treated cases of hydrocephalus) to incompatibility with life (as in anencephaly and severe spina bifida).
Folic Acid and Prevention of Birth Defects
Spina bifida and anencephaly are the most common NTDs and together affect approximately 4,000 pregnancies yearly.3 Prenatal screening programs have led to early detection of NTDs and the option to terminate an NTD-affected pregnancy. Fetal death and stillbirths are also more common in NTD-affected pregnancies. Despite this, some 2,500 to 3,000 children are born with these defects each year in the U.S.
Clinical trials have clearly shown that folic acid supplementation before conception and during the first trimester (13 weeks) of pregnancy reduces both the recurrence of NTDs in women with previous NTD-affected pregnancies 4 as well as the first-time occurrence of NTDs.5
Based on the results of these trials, the U.S. Public Health Service recommended in 1992 that all women of reproductive age who are capable of becoming pregnant should consume 400 mcg of folic acid per day.6 However, a 1998 survey found that only 29% of U.S. women were following this recommendation.7
Folic Acid Fortification of Food
In March 1996, prior to the Public Health Service survey, the Food and Drug Administration (FDA) authorized manufacturers to add folic acid to enriched grain products in an attempt to reduce the occurrence of NTDs. This recommendation became mandatory on January 1, 1998. The FDA directive required that all enriched cereal grains must to be fortified with 140 mcg of folic acid per 100 grams of grain.8 This meant that everything from bread to tortillas was fortified with folic acid.
Data from the 1999 National Health and Nutrition Examination Survey documented significant rises in the levels of folate (a form of folic acid) in the blood of reproductive-age women in the U.S.9—an indicator that, in the same group of women, food fortification with folic acid was overcoming the reluctance shown in 1998 to supplement the vitamin.
But Is It Enough?
The new JAMA study is the first attempt to measure the actual impact of folic acid fortification on the occurrence of NTDs. Although the use of birth certificate data must be viewed as imprecise, the 19% reduction in NTDs is consistent with previous estimates by other researchers of an 18–22% reduction in NTDs accompanying the intake of 100 mcg of additional folic acid per day.10 11 However, the actual reduction in NTD rates found in the new study is far less than what might be achieved by higher amounts of the vitamin. Researchers have estimated that intake of 200 mcg per day could reduce the incidence of NTDs by 35–41%, while the addition of 400 mcg per day is estimated to reduce the incidence by 47–53%.10 11
In their JAMA editorial, Drs. Mills and Shepard conclude, “Meanwhile, women of childbearing age should be advised to take a vitamin supplement containing 400 mcg/day of folic acid to obtain the maximum protection against the development of NTDs.”12
So, while the fortification of grains with folic acid appears to be a step in the right direction, a significant gap remains between the current findings and the level of prevention that has been reported at higher daily intakes of folic acid. The U.S. government should work with health educators to increase awareness among women of reproductive age who may become pregnant that taking additional folic acid in vitamin supplements will decrease their risk of having an NTD-affected pregnancy, even beyond the protection afforded by eating fortified foods. Providing low-income women with reduced-cost or free folic acid supplements would significantly help this process.References