Folic Acid Receives Ringing Endorsement as a Key Supplement
For decades we’ve known that vitamins are essential for health--indeed, for life itself. But, for almost as long, researchers and nutritionists have debated whether vitamin supplements are necessary to boost the amount of these nutrients we get naturally from food.
Most of the attention in this controversy has been given to the so-called antioxidant vitamins: C, E and A. And the discussion continues, because continuing research seems to support both sides of the argument, in some cases showing benefits for supplementation, and, in others, revealing some potentially detrimental effects. Ironically, one of the least publicized nutrients, the B vitamin known as folic acid, has now received almost universal endorsement for supplementation.
Research has conclusively demonstrated that folic acid deficiency increases the risk of serious birth defects of the brain and spine, known as neural tube defects, and there is strong evidence that folic acid supplementation can prevent these defects. The two most common NTDs--spina bifida (failure of the spine to close properly) and anencephaly (incomplete development of the brain)--affect about one of every 1,000 pregnancies in the United States. Experts estimate that 50% to 70% of these birth defects could be prevented if women consumed sufficient amounts of folic acid leading up to and during the first several weeks of pregnancy.
Substantial amounts of folic acid can be found in dark green leafy vegetables such as broccoli and spinach, citrus fruits such as oranges and grapefruit, and beans and legumes. Liver and other types of organ meats are also rich in folic acid. Enriched grain products, such as pasta, rice, bread, flour and cereals, are another excellent source. But in spite of the wide variety of foods that are rich in folic acid, surveys show that most Americans still do not consume adequate amounts of this important nutrient through dietary sources alone.
The evidence in support of folic acid supplementation is now so strong that the U.S. Public Health Service recommends that all women of childbearing age consume 400 micrograms (0.4 milligrams) of folic acid every day. Many experts (including the highly respected National Institute of Medicine) recommend that women of childbearing age rely on synthetic folic acid contained in fortified foods or vitamin supplements to reach this level.
These recommendations are made for all women who are capable of becoming pregnant, whether they plan to or not, because so many pregnancies are unintended, and once a pregnancy is underway it’s too late to start the supplementation. Neural tube defects occur very early in fetal development (usually within the first 28 days of pregnancy, which is just two weeks after the first menstrual period has been missed). Therefore, many birth defects due to folic acid deficiency are likely to have occurred before a woman even recognizes she is pregnant. To be effective, adequate amounts of folic acid must be consumed before and during this critical period. A woman who waits to learn she is pregnant before dealing with her baby’s need for folic acid has waited too long.
Unfortunately, studies show that many American women are not aware of the critical role that folic acid plays in preventing birth defects or of the need for adequate levels of consumption. A recent survey found that while 68% of women of childbearing age had heard or read about folic acid, only 32% were taking a vitamin supplement containing folic acid on a daily basis. Less than 15% were actually aware that folic acid helps prevent birth defects.
Folic acid may offer additional benefits to men as well and to women beyond their childbearing years. Research shows that dietary folic acid reduces blood levels of homocysteine, an amino acid associated with an increased risk of cardiovascular disease. One study showed that men and women who had homocysteine levels in the high normal range were more than twice as likely as those with lower normal levels to suffer cardiovascular events such as heart attack and stroke.
Some scientists believe increasing dietary intake of folic acid will lower the risk of heart attack and stroke by driving down homocysteine levels. However, this opinion is still under study and remains unproven, so supplementation with folic acid to prevent cardiovascular disease is not currently widely recommended.
Folic acid may also reduce the risk of some cancers, including colon and breast cancer. In one study, women who used multivitamins containing folic acid for 15 years or more were 75% less likely to develop cancer of the colon than women who didn’t.
Additional studies must be done before it can be concluded that folic acid supplementation plays a significant role in cancer prevention.
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Dr. Jonathan Fielding is the director of public health and the health officer for the Los Angeles County Department of Health Services. Dr. Valerie Ulene is a board-certified specialist in preventive medicine practicing in Los Angeles. Send questions by e-mail to ourhealth@dhs.co.la.ca.us. Their column appears the second and fourth Mondays of the month.
