Folate is vitamin B9. It helps the body make red blood cells. Folate is needed for healthy cell growth and function. The nutrient is very important during early pregnancy to lower the risk of birth defects of the brain and spine.

Folate is found mainly in dark green leafy vegetables, beans, peas and nuts. Fruits rich in folate include oranges, bananas, melons and papayas. The human-made form of folate is folic acid. It's an essential part of prenatal vitamins. Folic acid also is in many fortified foods, such as cereals and pastas.

People who don't eat enough foods rich in folate or folic acid may have low folate levels, called folate deficiency. That means their bodies don't get all the folate they need. People who have conditions that prevent the small intestine from taking in nutrients from foods also may have low folate levels. Examples of these conditions include celiac disease and inflammatory bowel disease.

The recommended daily amount of folate for adults is 400 micrograms (mcg). People who are planning pregnancy or could become pregnant should get 400 to 800 mcg of folic acid a day.

Research on the use of folate and folic acid supplements for specific conditions shows:

• Birth defects. Folic acid supplements can prevent birth defects that affect the brain and spinal cord. Taking a daily prenatal vitamin can help make sure you get enough folic acid. If you plan to get pregnant, take the supplement at least one month before trying to get pregnant and until at least 12 weeks into pregnancy.
• Folate deficiency. Take a folic acid supplement if you have trouble absorbing or getting enough folate in your diet. Many countries add folic acid to foods, such as cereals and pasta. So most people rarely need to take folic acid supplements.
• Heart and blood vessel disease and stroke. Folic acid works with vitamins B-6 and B-12 to control high levels of homocysteine in the blood. Too-high homocysteine levels might raise your risk of heart and blood vessel conditions, also called cardiovascular disease. Taking folic acid supplements also may lower your stroke risk.
• Cancer. Some research suggests that folate might lower the risk of various cancers.
• Depression. Some evidence suggests that folic acid might be a helpful supplement in treating depression.
• Dementia. There isn't enough evidence to support taking folic acid to prevent dementia.
• Autism spectrum disorder. Some research suggests that taking folic acid when pregnant may help lower the risk of autism spectrum disorder in the child.

When taken by mouth at suggested doses, folic acid is likely safe.

Taking high doses of folic acid by mouth can cause:

• A bitter taste in the mouth.
• Nausea.
• Loose stools.
• Confusion.
• Irritability.
• Trouble sleeping.
• Stomach cramps.

People with allergies might have a reaction to folic acid supplements. Warning signs of an allergic reaction include:

• Skin rash.
• Itching.
• Skin color changes, such as purple or brown depending on your skin color.
• Difficulty breathing.

If you take too much folic acid, it comes out of the body in urine.

When a person takes a high amount of a folic acid supplement, it can be hard to know if the person has enough vitamin B-12. Taking folic acid supplements can help correct low blood counts, but it won't repair nerve damage from not having enough vitamin B-12. Taking a supplement that has 100% of the Daily Value of both folic acid and vitamin B-12 can help prevent this issue.

Possible interactions include:

• Anticonvulsants. Taking folic acid with carbamazepine (Carbatrol, Tegretol, others), phenytoin (Dilantin, Phenytek) or valproate might lower the amount of the medicine in the blood.
• Barbiturates. A barbiturate is a medicine that acts as a central nervous system depressant. If you take folic acid with a barbiturate, the medicine might not work as well.
• Methotrexate (Trexall). Taking folic acid with this medicine when used to treat cancer could affect how well it works.
• Pyrimethamine (Daraprim). Taking folic acid with this medicine used to prevent malaria might affect how well it works.