First discovered in the early 1940s, folic acid (also known as folate, folacin, pteroylmonoglutamate, or vitamin B-9) is a water-soluble vitamin that takes part in a wide variety of body processes, from DNA synthesis to nerve signal transmission. Because it is water-soluble and is not stored in the body, it is important to consume folic acid every day. It may be difficult to get sufficient folic acid from dietary sources because it is easily lost during cooking, processing, and storage. Supplemental folic acid is usually found in the form of a multi-vitamin or a B-complex vitamin supplement.
The best food sources of folic acid include green leafy vegetables like spinach and kale, whole grains, enriched grain products, legumes, asparagus, broccoli, cabbage, and oranges.
Folic acid works together with vitamin B-12 in a variety of body processes. Because it is required for DNA synthesis, it is crucial for cellular division, and thus to the growth and repair of tissues. Folic acid is critical to the development of the fetal nervous system, and folic acid deficiency has been linked to neural tube defects like spina bifida, 1and a variety of other birth defects. For this reason, the U.S. Public Health Service recommends that all women who are or may become pregnant consume 400 mcg of folic acid per day, and the FDA now requires several enriched grain products to include folic acid. Folic acid is involved in the production of many neurotransmitters and is essential for healthy red blood cells. Symptoms of folic acid deficiency include anemia, diarrhea, irritability, weight loss, gastrointestinal disturbances, and elevated homocysteine.
The recommended intake for folic acid is 400 mcg per day. Higher doses should only be used under a physician's supervision. Folic acid is well tolerated, with no adverse side effects at this dosage. Extremely high doses (5 to 10 mg) may cause flatulence, nausea, and loss of appetite. The main concern with folic acid supplementation is that it can mask an underlying vitamin B-12 deficiency. Supplementing the two vitamins together is preferable because it alleviates this concern, and because they complement each other's activity.