The reason you hear so much about folic acid and pregnancy is because this B vitamin protects against a group of serious birth defects. However, if you're like most women, you don't get enough folic acid (officially known as B9) from your diet alone. For this reason, doctors often recommend that women who are pregnant or trying to conceive take prenatal vitamins containing folic acid.
What's the evidence?
Studies have shown that getting enough folic acid before conception and during the early months of pregnancy can prevent up to 70 percent of birth defects known as neural tube defects. These types of birth defects, which include spina bifida and anencephaly, are among the most serious birth defects. Spina bifida occurs when the fetus' spinal column does not close to protect the spinal cord. It can cause severe neurological problems and sometimes mental retardation. Anencephaly is a condition in which the baby's brain does not develop properly and most or all of the brain tissue is absent.
Since the late 1990s, the Food and Drug Administration (FDA) has required manufacturers to fortify some grain products, including flour, pasta, and rice, with folic acid to ensure that women get more of the vitamin in their diets. The program has been a great success. The incidence of neural tube defects decreased by one-third in the U.S. since folic acid fortification was implemented.
How much folic acid do I need?
The U.S. Public Health Service recommends that all women of childbearing age take at least 400 micrograms of folic acid a day, the amount contained in many multivitamins. However, most prenatal vitamins contain at least 600 micrograms, which is the amount recommended for pregnant women by the Institute of Medicine. (The IOM also allows for up to 1,000 micrograms of folic acid daily during pregnancy, if you are over 18.) If you're pregnant or even hoping to conceive, your health-care provider may suggest that you take the higher amount.
You don't need to be concerned about getting too much because folic acid is water-soluble, meaning your body will flush out any excess. Don't panic if you didn't know you were pregnant and failed to take folate right away. Neural tube defects are uncommon even among those who don't take supplements. But because the baby's neural tubes close during the first four weeks of development, it's important to start taking folic acid if there's any chance you might conceive, or as soon as you know you're pregnant. Folic acid is most protective against birth defects during this period.
"The key is that taking folate can reduce a low baseline risk much closer to zero," says Michael Potter, M.D., associate professor at the University of California at San Francisco's School of Medicine. "So everyone planning a pregnancy, or in the early stages of pregnancy, should take it. It's such an easy thing to do."
Can I get enough folic acid from my diet?
Folic acid is the synthetic form of folate, which is found naturally in some foods, including leafy vegetables, beans, citrus fruits, and whole grains. But it's best to take a prenatal vitamin containing folate in case you don't get enough from your meals. If you have severe morning sickness and can't tolerate prenatal vitamins, make sure to take a separate folic acid supplement.
Which foods are especially high in folate?
One of the best sources is leafy green vegetables, so salads can be a good choice. Flour, rice, and pasta are all fortified with folic acid, so meals that include these ingredients are also good for you. If, by any chance, you like liver, it's the best source of folic acid of all: One serving of chicken liver has 770 micrograms!
Sources: 1/2 cup lentils: 180 mcg; 1/2 cup fortified cereal: 100 to 400 mcg; 1/2 cup chickpeas: 141 mcg; 1/2 cup cooked spinach: 131 mcg; 1/2 cup black beans: 128 mcg; 1/2 cup asparagus: 132 mcg.
What are the signs of a folic acid deficiency?
Unfortunately, there aren't many signs. You probably wouldn't know if you weren't getting the recommended daily allowance of folic acid. But because folic acid promotes the growth of red blood cells, a serious deficiency can mimic the symptoms of iron-deficiency anemia, which include fatigue, weakness, headache, and irritability.
March of Dimes. Folic Acid. February 2010. http://www.marchofdimes.com/pnhec/173_769.asp
Center for the Evaluation of Risk to Human Reproduction: Report on Folic Acid. National Institutes of Health. http://cerhr.nichs.nih.gov/genpub/topics/folic_acid-ccae.html
American College of Obstetricians and Gynecologists. Folic Acid Administration Policy Highly Successful in Reducing Neural Tube Defects. News research from the February 27, 2004.
Women's Healthwatch. More on Folic Acid: Boosting Sperm Count. Pharmacy Times. 2003.
Folic Acid (Folate). The Merck Manual.
Curtis, Glade, B. and Schuler, Your Pregnancy week by week. Di Capo Press, Cambridge, Mass. 2007
Office of Dietary Supplements. Folate. http://ods.od.nih.gov/factsheets/folate.asp