Folate (folic acid), with vitamin B12, is necessary for the formation of normal red blood cells and the synthesis of DNA (deoxyribonucleic acid), which is the genetic material of cells. Folate is also necessary for normal development of a fetus's nervous system. A low intake of folate may increase the risk of bone fractures in older adults.
In the United States and Canada, folate is added to enrich foods made from grains. Folate in supplements or in enriched foods is easier for the body to absorb than the folate that occurs naturally in food.
Because the body stores only a small amount of folate, a diet lacking in folate leads to a deficiency within a few months. Folate deficiency is common because many people do not eat enough raw leafy vegetables or citrus fruits. Also, prolonged cooking destroys much of the folate in food.
Common causes of deficiency include
People who drink large amounts of alcohol do not consume enough folate because they often substitute alcohol for food. Such people are often generally undernourished. Alcohol consumed in large amounts also interferes with the absorption and processing (metabolism) of folate.
Folate deficiency may also result from
Malabsorption disorders (such as celiac disease) interfere with absorption of folate.
Women who are pregnant or breastfeeding and people undergoing dialysis may develop this deficiency because their need for folate is increased.
Many anticonvulsants (such as phenytoin and phenobarbital) and drugs used to treat ulcerative colitis (such as sulfasalazine) decrease the absorption of this vitamin. Methotrexate (used to treat cancer and rheumatoid arthritis), triamterene (used to treat high blood pressure), metformin (used to treat diabetes), and trimethoprim-sulfamethoxazole (an antibiotic) interfere with the metabolism of folate.
Folate deficiency causes an anemia similar to that due to vitamin B12 deficiency (see Vitamin B Deficiency and see Vitamin Deficiency Anemia).
Anemia develops gradually and may be more severe than symptoms suggest. Fatigue may be the first symptom.
In addition to the general symptoms of anemia (such as paleness, irritability, shortness of breath, and dizziness), folate deficiency, if severe, may result in a red and sore tongue, a reduced sense of taste, weight loss, and depression.
If a pregnant woman has folate deficiency, her infant may have a birth defect of the spinal cord or brain (neural tube defect).
If a blood test detects large red blood cells in people who have anemia or who are undernourished, doctors measure the folate level in a blood sample. A low level indicates this deficiency. Doctors also measure the vitamin B12 level to rule out vitamin B12 deficiency because this deficiency can also result in anemia and large red blood cells.
Prevention and Treatment
As a preventive measure, people who are taking drugs that interfere with the absorption or metabolism of folate should take a folate supplement.
Women who are pregnant or who could become pregnant should take folate supplements to reduce the risk of having an infant with a birth defect, mainly neural tube defects. Women who have had a baby with a neural tube defect are often prescribed higher doses of folate.
Folate supplements do not protect against coronary artery disease or stroke. There is no evidence that folate supplements reduce or increase the risk of various cancers. Folate supplements do not seem to improve cognitive function in older adults.
Taking daily doses of a folate supplement by mouth effectively treats the deficiency.
Folate is generally not toxic.
If people with vitamin B12 deficiency take very high doses of folate, doctors may be delayed in recognizing the nerve damage due to vitamin B12 deficiency. Because the diagnosis is delayed, nerve damage may be more severe and more difficult to treat.
Last full review/revision October 2014 by Larry E. Johnson, MD, PhD