Folic Acid

Daily Value: 400 micrograms

Good Food Sources: Fortified cereals, pinto beans, navy beans, asparagus, spinach, broccoli, okra, brussels sprouts

Folic acid is a nutritional powerhouse that makes things happen within the body. It works with approximately 20 different enzymes to build DNA, the material that contains the genetic code for your body, and is essential for normal nerve function.

It also seems to prevent heart disease and stroke by reducing the body's levels of homocysteine, an artery-attacking chemical that accumulates in the blood of people who eat meats.

What's more, folic acid may help protect against cancers of the lung, colon and cervix. In a study at the University of Alabama in Birmingham, researchers found that women whose cervical cells were loaded with folate (the naturally occurring form of folic acid) were two to five times less likely than women with low folate levels to develop cervical dysplasia when exposed to various risk factors such as cigarette smoke, the human papillomavirus, contraceptives and childbirth. (Cervical dysplasia is a condition involving the development of abnormal cells in the cervix. This condition can progress to cancer in some women.)

Folic acid also protects a woman's fetus from life-threatening birth defects of the brain and spine. Unfortunately, a survey by the March of Dimes has found that 90 percent of women of reproductive age are unaware of this fact, and only 15 percent are aware that the federal government has recommended that all women capable of bearing children get 400 micrograms of folic acid every day. This amount of folic acid is available in a multivitamin/mineral supplement. Still, only 28 percent of the women surveyed take a vitamin containing folic acid every day.

Using Folic Acid Safely

Folic acid has virtually no side effects, even when taken in high amounts, although one study did find that people taking 15 milligrams (15,000 micrograms) a day complained of nausea, bloating, problems sleeping and irritability. Doses of more than 400 micrograms a day can mask symptoms of pernicious anemia, a potentially fatal vitamin B₁₂­deficiency disease.

"In general, 0.4 milligram (400 micrograms) of folate is a good amount to get in a day, and with careful planning that can be achieved," says Meir Stampfer, M.D., Dr.P.H., an investigator at the Harvard School of Public Health. A day's worth of folate could look like this: one cup of orange juice (110 micrograms) and one cup of folate-fortified cereal (160 micrograms) plus a cup of raw spinach in a lunch or dinner salad (130 micrograms). Although folate is available in these and many other foods, be aware that as much as 50 percent of the nutrient is destroyed during food processing, storage and household preparation. In general, much of the folate in foods is killed by heat and light.

Several substances can increase your need for the vitamin, including alcohol, tobacco, aspirin and other nonsteroidal anti-inflammatory drugs, oral contraceptives, pancreatic extracts, estrogen, antacids, arthritis drugs such as methotrexate and medications prescribed for convulsions, malaria and bacterial infections.