Scientists are studying folate to understand how it affects health. Here are several examples of what this research has shown.
Neural tube defects
Taking folic acid before becoming pregnant and during early pregnancy helps prevent neural tube defects in babies. Neural tube defects are major birth defects in a baby’s brain (anencephaly) or spine (spina bifida). But about half of all pregnancies are unplanned. Therefore, all women and teen girls who could become pregnant should consume 400 mcg of folic acid daily from supplements, fortified foods, or both, in addition to the folate they get from following a healthy eating pattern.
Since 1998, the U.S. Food and Drug Administration (FDA) has required food companies to add folic acid to enriched bread, flour, cornmeal, pasta, rice, and other grain products sold in the United States. In 2016, the FDA allowed manufacturers to voluntarily add folic acid to corn masa flour. Because most people in the United States eat these foods, folic acid intakes have increased since 1998, and the number of babies born with neural tube defects has decreased.
Cancer
Folate that is naturally present in food may decrease the risk of several forms of cancer. But folate supplements might have different effects on cancer risk depending on how much the person takes and when. People who take recommended amounts of folic acid before cancer develops might decrease cancer risk, but taking high doses after cancer (especially colorectal cancer) begins might speed up its progression. For this reason, people should be cautious about taking high doses of folic acid supplements (more than the upper limit of 1,000 mcg), especially if they have a history of colorectal adenomas (which sometimes turn into cancer). More research is needed to understand the roles of dietary folate and folic acid supplements in cancer risk.
Depression
People with low blood levels of folate might be more likely to have depression. In addition, they might not respond as well to antidepressant treatment as people with normal folate levels.
Folate supplements, particularly those that contain methylfolate (5-methyl-THF), might make antidepressant medications more effective. But whether supplements help both people with normal folate levels and those with folate deficiency isn’t clear. More research is needed to better understand the role of folate in depression and whether folate supplements are helpful when used in combination with standard treatment.
Heart disease and stroke
Folic acid supplements lower levels of homocysteine, an amino acid in the blood that’s linked to a higher risk of cardiovascular disease. But the supplements don’t directly decrease the risk of heart disease. Some studies have shown that a combination of folic acid with other B-vitamins, however, helps prevent stroke.
Dementia, cognitive function, and Alzheimer's disease
Folic acid supplements, with or without other B-vitamins, do not seem to improve cognitive function or prevent dementia or Alzheimer’s disease. But more research on these topics is needed.
Preterm birth, congenital heart defects, and other birth defects
Taking folic acid might reduce the risk of having a premature baby or a baby with birth defects, such as certain types of heart problems. But more research is needed to understand how folic acid affects the risk of these conditions.
Autism Spectrum Disorder (ASD)
ASD affects communication and behavior, usually beginning by age 2. People with ASD have limited interests, repetitive behaviors, and difficulty communicating and interacting with others.
Some studies have shown that taking recommended amounts of folic acid before and during early pregnancy may help reduce the risk of ASD in the child. However, because the study results are inconclusive, more research is needed to understand the potential role of folic acid in lowering the risk of ASD.