Folic acid is a synthetic form of vitamin B9 that’s often added to fortified foods and used in supplements. It has numerous benefits, and some risks.

Folic acid is a water-soluble vitamin. It’s a synthetic version of folate, one of the B vitamins (1).

Because your body can’t make folate, you need to get it from your diet.

Some foods naturally contain folate. Folic acid is added to other foods. You can also get folic acid from dietary supplements (2).

What’s the difference between folate and folic acid?

Although the terms “folate” and “folic acid” are often used interchangeably, they are actually different forms of the same vitamin: vitamin B9.

Folic acid has a different structure than folate and has slightly different effects in your body. “Folate” is the generic name that encompasses all forms of vitamin B9, including folic acid and 5-MTHF. Folic acid is a specific synthetic form of this vitamin (1, 2, 3).

You can find folate in plant and animal foods like these (1):

• spinach
• kale
• broccoli
• avocado
• citrus fruits
• eggs
• beef liver

Folic acid is added to foods such as flour, ready-to-eat breakfast cereals, and breads (4, 5).

It’s also in dietary supplements, such as multivitamins (1, 4).

What does the body use folate for?

Your body uses folate to (1):

• make and repair DNA
• help cells grow, divide, and work properly
• produce certain proteins
• help red blood cells mature

Folate deficiency can lead to many health problems, including (1, 2, 6, 7):

• anemia
• an increased risk of heart disease and certain cancers
• developmental irregularities in infants if pregnant people don’t get enough folate

Many countries, including the United States, require certain grain products to be fortified with folic acid. Folic acid fortification helps prevent neural tube irregularities in infants (7, 8).

Summary

Folic acid is a synthetic version of the B vitamin folate, which naturally occurs in leafy greens, eggs, and citrus fruits, among other foods. It’s essential to important functions in the body.

Recommended intake levels 

The Recommended Dietary Allowance (RDA) for folate is listed in Dietary Folate Equivalents (DFEs). This unit of measure accounts for the differences in how your body absorbs folate from foods and folic acid from fortified foods and supplements.

Your body absorbs natural folate about half as well as folic acid from supplements (1).

Adults need about 400 mcg DFE of folate each day. During pregnancy and breastfeeding, folate needs can increase. The RDA during pregnancy is 600 mcg DFE (1, 6, 7, 9).

Your body stores 15–30 mg of folate. Most of that folate is in your liver, and the rest is in your blood and tissues (1).

The RDA for folate for infants, children, and teens is (1):

• Birth to 6 months: 65 mcg DFE
• Ages 7–12 months: 80 mcg DFE
• Ages 1–3: 150 mcg DFE
• Ages 4–8: 200 mcg DFE
• Ages 9–13: 300 mcg DFE
• Ages 14–18: 400 mcg DFE

Summary

Adults need about 400 mcg DFE of folate each day.

Benefits and uses

Both folic acid and folate are used in supplements. Although these two nutrients treat the same conditions, they are metabolized differently in the body and can affect health in different ways (1).

Here are some common uses and benefits of folic acid supplements.

Treating folate deficiency

Folate deficiency can happen for many reasons. Some possible causes of folate deficiency are (1, 2):

• a lack of folate in your diet
• diseases or surgeries that affect how your body absorbs folate, including celiac disease, short bowel syndrome, and gastric bypass surgery
• no stomach acid (achlorhydria) or low stomach acid (hypochlorhydria)
• drugs that affect folate absorption, including methotrexate and sulfasalazine (Azulfadine)
• alcohol use disorder
• pregnancy
• hemolytic anemia
• dialysis

Consuming too little folate can cause complications such as anemia, fetal development issues, mental impairment, impaired immune function, and depression. Taking folic acid or folate supplements can bring up your levels and prevent these complications (6, 7, 9, 10).

Preventing birth defects and pregnancy complications

Folic acid supplements can help to prevent neural tube irregularities, including spina bifida and anencephaly. Getting enough folic acid during pregnancy can reduce the chance that your baby will be born with one of these conditions (7, 9).

Folic acid supplements not only help prevent fetal development issues but also help lower the risk of pregnancy complications such as preeclampsia (10).

Maintaining brain health

Low blood folate levels are linked to poor mental function and an increased risk of dementia. Even folate levels that are technically normal but on the low side might increase the risk of mental impairment in older adults.

Adequate folate intake may also help protect against Alzheimer’s disease (11, 12).

In a 2019 study in 180 adults with mild cognitive impairment, taking 400 mcg of folic acid supplements daily for 2 years improved measures of brain function and reduced blood levels of proteins that are involved in Alzheimer’s disease (13).

Another study looked at 121 people with newly diagnosed Alzheimer’s disease who were being treated with the medication donepezil (Aricept).

Those who also took 1,250 mcg of folic acid per day for 6 months had improved thinking ability and less inflammation than those who took Aricept alone (14).

Treating mental health conditions

Folate is involved in the production of brain chemicals called neurotransmitters. Consuming too little folate has been linked to depression, schizophrenia, and other mental health conditions.

For example, people with depression may have lower blood levels of folate than people without depression (15).

A 2022 review of studies suggests that folic acid and folate supplements may help reduce symptoms of mental health conditions such as postpartum depression, schizophrenia, and bipolar disorder (16).

Taking folate supplements in addition to antidepressant medication may reduce depression symptoms more than taking antidepressant medication alone (17).

A review of seven studies found that treatment with folate supplements plus antipsychotic medication may improve symptoms in people with schizophrenia more than antipsychotic medication alone (18).

However, larger, more robust studies are needed to further support these findings.

Reducing heart disease risk factors

Folate-based supplements, including folic acid, may help improve heart health and reduce the risk of heart disease.

High levels of the amino acid homocysteine are thought to increase heart disease risk. Because folate helps break down homocysteine, low folate can lead to high homocysteine levels, also known as hyperhomocysteinemia.

Folic acid supplements can help bring down homocysteine levels and may lower heart disease risk (19).

For example, a review that included 30 studies with more than 80,000 total participants showed that supplementing with folic acid led to a 4% reduction in overall heart disease risk and a 10% reduction in stroke risk (19).

What’s more, using folic acid supplements along with antihypertensive medications may reduce high blood pressure significantly more than antihypertensive medications alone. Folic acid supplements may also improve blood vessel function in people with heart disease (20, 21).

Other possible benefits

Folic acid supplements may also help with these other health conditions:

• Diabetes. Folate supplements may help improve blood sugar regulation and reduce insulin resistance in people with diabetes. Because the diabetes drug metformin can lower folate levels, you may need a supplement if your levels are low (22, 23, 24).
• Fertility issues. Folate can improve egg quality and help eggs grow and implant in the uterus. Taking folate may increase the chance of getting pregnant and carrying a baby to term. People who use assisted reproductive technology to conceive may be more likely to have a baby if they have a higher intake of supplemental folate (25, 26).
• Inflammation. Inflammation plays a role in many diseases. Folic acid and folate supplements have been shown to reduce markers of inflammation such as C-reactive protein (27).
• Kidney disease. The kidneys usually filter waste out of the blood, but when the kidneys are damaged, homocysteine can build up. About 85% of people with chronic kidney disease have too much homocysteine in their blood. Folic acid supplements may help reduce homocysteine levels and heart disease risk in people with kidney disease (28).

Larger studies are still needed to confirm the benefits of folate supplementation.

This list doesn’t include every possible benefit of folic acid. There are many other reasons people may use folate-based supplements.

Consult a healthcare professional

Before starting folic acid supplements, it’s important to talk with a healthcare professional. They can make sure the supplements will not interact negatively with other medications you may be taking.

Summary

Folic acid supplements are commonly used to prevent fetal development issues in pregnant people. Low levels of folate can be associated with health risks, and a deficiency of this essential nutrient may be caused by a medical condition.

Folic acid for pregnancy

Folate plays essential roles in a baby’s development.

It’s involved in cell division and tissue growth. It also helps the baby’s brain and spine, called the neural tube, develop. Taking folic acid both before and during pregnancy can help prevent neural tube irregularities such as anencephaly and spina bifida (1, 7, 8).

The U.S. Preventive Services Task Force, an independent panel of national disease-prevention experts, recommends that anyone who is trying to become pregnant start taking a daily folic acid supplement containing 400–800 mcg at least 1 month before becoming pregnant and through the first 2–3 months of pregnancy (9).

However, the common recommendation in practice encourages people capable of getting pregnant — of childbearing age and engaging in sexual activity that could result in pregnancy — to take a folic acid supplement, because many pregnancies can be unplanned (6, 7, 9).

Since the 1990s, flour and other foods have been fortified with folic acid. Consuming both fortified foods and folic acid supplements before and during pregnancy can help reduce the risk of neural tube irregularities (5, 7, 8).

Beyond preventing fetal development issues, taking folic acid supplements during pregnancy may improve a child’s mental function and reduce the chance of the child developing autism spectrum disorder (ASD).

However, taking too much folic acid may have a negative effect on a child’s brain development and increase their chances of developing autism, which will be discussed in the next section (29).

Folate is also important for the health of the pregnant person. Supplementing with folic acid has been shown to reduce the risk of pregnancy-related complications, including preeclampsia. Higher folate levels in a pregnant person may lower the risk of preterm birth (10, 30).

Folate is important for the health of both pregnant people and their babies, and it’s not always easy to get enough of this nutrient through your diet alone (6, 7, 9).

Summary

Folic acid supplements help support pregnancy, reduce pregnancy-related complications, and reduce the chance of fetal development issues.

Gene changes that affect folate levels

When you take folic acid, your liver has to convert it into the active form, 5-methyltetrahydrofolate (5-MTHF).

If your liver doesn’t convert it quickly enough, folic acid can build up in your blood. Eating foods containing 5-MTHF instead of folic acid can prevent this from happening (1).

Foods that contain 5-MTHF include (1):

• leafy greens
• beans and lentils
• asparagus
• avocado

Certain gene changes affect how your body uses folate. Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that breaks down homocysteine. Changes called mutations in the code for MTHFR can affect your health by changing folate levels in your body (2).

One of the most common mutations to MTHFR is C677T. People with this variant have less activity of an enzyme that breaks down homocysteine. They may have high levels of homocysteine, which could increase their heart disease risk.

In a pregnant person, this variant can also increase the chance of neural tube irregularities in a developing fetus (2, 31).

There are genetic tests for MTHFR variants, but few people need them.

Having an MTHFR mutation alone doesn’t mean you’re at risk of health problems or that you need treatment. But if your homocysteine levels are high, a healthcare professional may recommend that you take a supplement (31).

Summary

Certain genetic mutations may affect the folate levels in your body.

Side effects and precautions

Eating folate-rich foods and taking natural forms of folate such as 5-MTHF are generally considered safe. But taking high doses of folic acid through supplements could potentially lead to a buildup of unmetabolized folic acid in your blood.

“Unmetabolized” means your body hasn’t broken down the folic acid or converted it into other forms of folate. No confirmed health risks due to unmetabolized folic acid have yet been found, but undiscovered risks may still exist (1, 32, 33, 34, 35).

It’s important to note that most children and adults in the United States get enough folate from food and don’t need to take a folic acid supplement (1).

Autism

Taking folic acid during pregnancy helps prevent neural tube irregularities. But having high levels of unmetabolized folic acid in your blood may increase the chance that your child will have ASD.

People who take less than 400 mcg of folic acid daily are unlikely to have high levels of unmetabolized folic acid in their blood (29, 36).

High levels of unmetabolized folic acid during pregnancy may affect children’s mental development.

In a study of 1,682 mother-child pairs, children whose mothers supplemented with more than 1,000 mcg of folic acid per day during pregnancy scored lower on a test of mental abilities than children whose mothers took 400–999 mcg per day (37).

Although these studies suggest there may be risks to taking high doses of folic acid during pregnancy, more research is needed to confirm these findings.

Other possible risks of high folic acid intake

Taking high doses of folic acid may be associated with other health conditions, including the following.

Cancer

Folic acid might lower the risk of cancers affecting the head and neck, pancreas, esophagus, and bladder. But it may increase the risk of prostate cancer.

So far, research on the topic has not delivered conclusive results, and more studies are needed.

But research suggests that folate may suppress some types of cancer during its early stages, while high doses of folic acid taken after precancerous cells have developed may cause cancer to grow and progress (1, 38, 39).

Impaired immune function

High dose folic acid supplements may suppress the immune system by reducing the activity of protective immune cells such as natural killer (NK) cells. Whether these immune changes could put people at increased risk of infection is still unknown (40).

Summary

Research has suggested that high folic acid intake may be associated with certain health conditions, including cancer, autism, and immune system suppression.

How to take 

Folate and folic acid can be found in many forms. They are added to multinutrient supplements, including multivitamins and B-complex vitamins. Most adult supplements contain 680–1,360 mcg DFE (400–800 mcg of folic acid) (1).

The Tolerable Upper Intake Level (UL) is the highest daily folic acid dose you can take without experiencing harmful side effects.

The UL includes only folate from fortified foods and dietary supplements. High intake of naturally occurring folate from food has not been shown to cause any adverse effects (1).

The UL for folate in supplements and fortified foods is (1, 32):

Age rangeULadults1,000 mcgchildren ages 14–18800 mcgchildren ages 9–13600 mcgchildren ages 4–8400 mcgchildren ages 1–3300 mcg

Most children in the United States get enough folate from food, and 30–66% of children ages 1–13 who take folic acid supplements exceed the UL for their age group. Ask a pediatrician before giving your child a folic acid supplement to make sure it’s safe (1).

You can take all forms of folic acid with or without food.

Before taking folic acid

A healthcare professional might recommend a folic acid supplement if you have a deficiency or you are pregnant or thinking about getting pregnant.

Let a healthcare professional know what other prescription and over-the-counter medications you take. Folic acid may interact with some medicines (1).

Storage and handling

Store folic acid supplements in a cool, dry place. Keep supplements away from humid areas, such as the bathroom.

Overdose

There’s no set upper limit for folate in foods. Because folate is water-soluble, your body removes any extra you consume. Still, it may be possible to develop side effects if you take folic acid supplements in amounts greater than the UL (1, 2).

A healthcare professional may recommend higher doses if you have a folate deficiency. Avoid taking more than the UL unless a healthcare professional directs you to do so.

Summary

The maximum amount of folic acid and folate adults can consume from supplements and fortified foods without experiencing harmful side effects is 1,000 mcg. Children typically get enough folate from food alone.

Interactions 

Folic acid supplements may interact with some commonly prescribed medications, including (1):

• methotrexate, which is used to treat some cancers and autoimmune diseases
• epilepsy medications such as phenytoin (Dilantin), carbamazepine (Carbatrol, Tegretol, others), and valproate (Depacon)
• sulfasalazine (Azulfadine), which is used to treat ulcerative colitis

If you’re taking one of these medications, ask your doctor before taking folic acid supplements.

Summary

Folic acid supplements may interact with some medications.

Use in certain groups

Folate supplements are especially important for people who (1, 2):

• are pregnant or of childbearing age
• have a condition that affect folate absorption, such as celiac disease or inflammatory bowel disease
• have gene changes that affect how their bodies break down and use folate
• are older and live in care facilities
• are at higher risk of folate deficiency because of their diet
• have alcohol use disorder

Avoid giving folate supplements to infants under 1 year old unless a healthcare professional recommends it. Breastmilk, formula, and food should be the only sources of folate in an infant’s diet (1).

Summary

People who are pregnant or of childbearing age or who have folate deficiencies often use folic acid supplements.

Alternatives

There are many versions of folate. Folinic acid, folic acid, and 5-methyltetrahydrofolate are the ones most widely used in dietary supplements (1).

Folinic acid is a natural form of folate found in foods. Healthcare professionals call it leucovorin. It’s used to prevent toxic side effects from the drug methotrexate, which is a treatment for some types of cancer (41).

Folinic acid is more effective than folic acid at raising blood folate levels (41).

Some studies have shown that 5-MTHF absorbs better than other forms of synthetic folate. Plus, it’s less likely to interact with medications. This suggests it may be better to take 5-MTHF supplements than folic acid. However, other studies have found no significant differences (42).

Summary

Folinic acid, folic acid, and 5-methyltetrahydrofolate (5-MTHF) are the types of folate most commonly used in dietary supplements.

Just one thing

If you’re considering getting pregnant, it’s recommended that you take a folic acid supplement and eat a diet high in folate. If you think you have a folate deficiency, a healthcare professional can diagnose it and help you get the folate you need.