Folate is the natural form of vitamin B9, water-soluble, and naturally found in many foods. It is also added to foods and sold as a supplement in the form of folic acid; this form is actually better absorbed than that from food sources—85% vs. 50%, respectively. Folate helps to form DNA and RNA and is involved in protein metabolism. It plays a key role in breaking down homocysteine, an amino acid that can exert harmful effects in the body if it is present in high amounts. Folate is also needed to produce healthy red blood cells and is critical during periods of rapid growth, such as during pregnancy and fetal development.
RDA: The Recommended Dietary Allowance for folate is listed as micrograms (mcg) of dietary folate equivalents (DFE). Men and women ages 19 years and older should aim for 400 mcg DFE. Pregnant and lactating women require 600 mcg DFE and 500 mcg DFE, respectively. People who regularly drink alcohol should aim for at least 600 mcg DFE of folate daily since alcohol can impair its absorption.
UL: A Tolerable Upper Intake Level (UL) is the maximum daily dose unlikely to cause adverse side effects in the general population. The UL for adults for folic acid from fortified food or supplements (not including folate from food) is set at 1,000 mcg a day.
A wide variety of foods naturally contain folate, but the form that is added to foods and supplements, folic acid, is better absorbed. In January 1998, the U.S. Food and Drug Administration required food manufacturers to add folic acid to foods commonly eaten, including bread, cereals, pasta, rice, and other grain products, to reduce the risk of neural tube defects. This program has helped to increase the average folic acid intake by about 100 mcg/day. Good sources of folate include:
- Dark green leafy vegetables (turnip greens, spinach, romaine lettuce, asparagus, Brussels sprouts, broccoli)
- Sunflower seeds
- Fresh fruits, fruit juices
- Whole grains
- Fortified foods and supplements
Signs of Deficiency and Toxicity
A folate deficiency is rare because it is found in a wide range of foods. However, the following conditions may put people at increased risk:
- Alcoholism. Alcohol interferes with the absorption of folate and speeds the rate that folate breaks down and is excreted from the body. People with alcoholism also tend to eat poor-quality diets low in folate-containing foods.
- Pregnancy. The need for folate increases during pregnancy as it plays a role in the development of cells in the fetus.
- Intestinal surgeries or digestive disorders that cause malabsorption. Celiac disease and inflammatory bowel disease can decrease the absorption of folate. Surgeries involving the digestive organs or that reduce the normal level of stomach acid may also interfere with absorption.
- Genetic variants. People carrying a variant of the gene MTHFR cannot convert folate to its active form to be used by the body.
Signs of deficiency can include: megaloblastic anemia (a condition arising from a lack of folate in the diet or poor absorption that produces less red blood cells, and larger in size than normal); weakness, fatigue; irregular heartbeat; shortness of breath; difficulty concentrating; hair loss; pale skin; mouth sores.
It is extremely rare to reach a toxic level when eating folate from food sources.
However, an upper limit for folic acid is set at 1,000 mcg daily because studies have shown that taking higher amounts can mask a vitamin B12 deficiency. This deficiency occurs most often in older adults or those eating a vegan diet in whom a B12 deficiency is more common. Both folate and B12 are involved in making red blood cells, and a shortage of either can result in anemia. A person taking high-dosage supplements of folic acid may be able to correct the anemia and feel better, but the B12 deficiency still exists. In this case, if high folate intake continues to “hide” the symptoms of B12 deficiency for a long time, slow but irreversible damage to the brain and nervous system may occur. If you choose to use a folic acid supplement, stick with the lower range available of 400 mcg a day or less, as you will likely obtain additional folic acid from fortified foods like cereals and bread, as well as natural folate in food.
Overall, the evidence suggests that the amount of folic acid in a typical multivitamin does not cause any harm—and may help prevent some diseases, especially among people who do not get enough folate in their diets, and among individuals who drink alcohol.
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