Folic Acid: Benefits and Risks Explained

What Is Folic Acid?

What Is Folic Acid?
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Updated on September 1, 2025
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Folic acid, also known as vitamin B9, is a form of vitamin B that helps your body make and maintain new cells. It’s essential for everyone, but it’s especially important during pregnancy because it plays a key role in preventing serious birth defects of the brain and spine.

Folic acid is found naturally in many fruits, vegetables, and legumes, and it’s sometimes added to foods like bread, cereal, and other grain products. People who don’t get enough in their diet can also take it as a dietary supplement.

What Is Folic Acid?

Folic acid is a form of folate, a B vitamin that naturally occurs in many foods. Your body uses it to make new cells — blood cells, brain cells, and skin, hair, and nail cells, to name a few.

Folate exists in many forms (such as THF and 5-MTHF), but folic acid is the most stable version. It’s used in supplements and in fortified foods like cereals and breads because it holds up to heat, light, and cooking.

Who Needs Folic Acid?

Everyone needs folate to support cell function, but folic acid is especially important during early pregnancy, when it helps form the neural tube, the structure that becomes the baby’s brain and spinal cord.

“All women of reproductive age should supplement folic acid to prevent neural tube defects in the first four weeks of pregnancy,” says Jennifer Frediani, PhD, RD, assistant professor at the Nell Hodgson School of Nursing at Emory University in Atlanta.

Most women don’t realize they are pregnant that early, so this is a preventative measure, says Dr. Frediani.

Folic acid is also used to treat or prevent folate deficiency anemia, and it may be recommended for people with certain medical conditions or those who take medications that interfere with folate absorption.

Women who aren’t pregnant and men typically get enough folate because it’s added to many common products like cereals and flour, says Frediani.

People who are at risk of not getting enough folate include:

  • Teenage girls ages 14 to 18 years, women ages 19 to 30, and non-Hispanic Black women
  • People with alcohol use disorder, due to poor diet quality and reduced folate absorption caused by alcohol
  • People with malabsorptive disorders, such as celiac disease and inflammatory bowel disease
  • People with an MTHFR gene variant, who have a reduced ability to convert folate into an active form that can be metabolized in the body.
These are the recommended daily amounts of dietary folate in micrograms (mcg) of dietary folate equivalents.

  • Teens 14 to 18 years old: 400 mcg
  • Adults 19 years and older: 400 mcg
  • Pregnant teens and women: 600 mcg
  • Breastfeeding teens and women: 500 mcg

Where Do You Get Folic Acid?

Folic acid is found in:

  • Fortified foods (labeled “enriched”) like bread, pasta, rice, and cereal
  • Multivitamins and prenatal vitamins
  • Individual folic acid supplements
Natural food sources of folate include:

  • Leafy greens (spinach, kale)
  • Legumes (lentils, black beans)
  • Avocados
  • Oranges
  • Asparagus
  • Brussels sprouts
  • Broccoli
  • Cantaloupe
  • Peanuts
Fortified foods and supplements make it easier to meet your daily folate needs, which is why the U.S. Food and Drug Administration has mandated folic acid fortification in grain products since 1998.

Foods Without Folic Acid

Some people seek out foods without folic acid to avoid synthetic additives or due to misinformation online. Here are examples of foods that are not fortified with folic acid:

  • Most organic and whole foods, including fresh fruits and vegetables
  • Unenriched grains (check labels)
  • Organic or specialty breads and cereals (not labeled “enriched”)

Keep in mind: These foods may contain natural folate even if they don’t contain folic acid.

Can Folic Acid Be Bad for You?

For most people, folic acid is very safe. The upper limit for adults is set at 1,000 mcg per day from supplements or fortified foods (not counting natural folate from food). Taking more than this long-term may mask a vitamin B12 deficiency.

Overall, the evidence shows that the amount of folic acid in a typical multivitamin doesn’t cause any harm, especially in people who don’t get enough folate in their diets.

Who Should Not Take Folic Acid?

People who are being treated for cancer or who have a history of certain cancers should talk with their doctor before taking any folic acid supplements.

“While the evidence is still somewhat mixed, it has been shown that supplemental folic acid in addition to fortified folic acid in the food supply could accelerate cancer development because of its role in DNA synthesis and cell division,” says Frediani.

Additionally, supplements in general, including folic acid, can sometimes interfere with cancer medications.

Folic Acid and Autism

A common myth is that folic acid is linked to autism in children. This stems largely from a study published in 2016 that showed a link between excessive amounts of folate consumption during pregnancy and an increased risk of autism in the offspring. The women in the study had very high levels of folate in their blood after giving birth — more than four times the level considered adequate.

Since the publication of that study, many other studies have shown the very opposite: Women who supplement with the appropriate amounts of folic acid are actually less likely to give birth to a child with autism.

A 2024 review looked at 52 studies involving more than 10,000 people with autism spectrum disorder.

 These studies examined vitamin intake (including folic acid, vitamin B6, and vitamin B12), blood levels of these vitamins, and whether taking folic acid helped with symptoms. They also looked at whether a mother’s folic acid intake during pregnancy affected her child’s risk of developing autism.

Key findings from the review include the following:

  • Many people with autism still don’t get enough folic acid.
  • There was no link between a mother’s folic acid intake and her child’s risk of autism.
  • Some people with autism saw improvements in communication, social skills, and behavior after taking folic acid, but results varied from person to person.
Researchers say more high-quality studies are needed to better understand the role of folic acid in autism spectrum disorder.

MTHFR and Folic Acid

MTHFR helps your body convert folic acid into its active form. Some people have a variation in this gene that may slightly reduce their ability to process folic acid efficiently.

This does not mean that people with this gene variant should avoid folic acid or take other types of folate, such as methylated folate (like 5-MTHF). People with the MTHFR gene variant can still process all types of folate, including folic acid.

“There is a lot of evidence to support that the standard dosing recommendation for people with this variant is fine,” says Annette Frain, RD, a weight management specialist at Atrium Health Wake Forest Baptist in Greensboro, North Carolina.

Studies show that having the variant alone doesn’t significantly affect how the body processes folate, and that having a relatively common MTHFR variant is not a reason to avoid folic acid.

That being said, women with this variant who are trying to get pregnant or are already pregnant should discuss folic acid supplementation with their doctor. Because of their reduced ability to process folic acid, they may want to explore alternate supplements to make sure they don’t accumulate unmetabolized folic acid.

The Takeaway

  • Folic acid, or vitamin B9, is essential for making new cells and is especially important before and during early pregnancy to prevent serious birth defects of the brain and spine.
  • Folic acid is found naturally in foods like leafy greens, legumes, and citrus fruits, and in fortified foods like bread, pasta, and cereals. Supplements can help people meet daily needs.
  • Most people tolerate folic acid well, but high doses over time can mask vitamin B12 deficiency, and people with certain cancers should consult their doctor before supplementing.
  • Research shows that the recommended folic acid intake does not increase autism risk, even in people with MTHFR gene variants, and it may offer other health benefits when deficiencies are addressed.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Folic Acid. MedlinePlus. July 13, 2023.
  2. About Folic Acid. Centers for Disease Control and Prevention. May 20, 2025.
  3. Folic Acid: Sources and Recommended Intake. Centers for Disease Control and Prevention. May 20, 2025.
  4. Folate Deficiency Anemia. Cleveland Clinic. September 12, 2022.
  5. Folate: Fact Sheet for Consumers. National Institute of Health: Office of Dietary Supplements. November 1, 2022.
  6. Folate (Folic Acid). Mayo Clinic. August 15, 2025.
  7. 18 Foods Filled With Folate Every Woman Should Know. UnityPoint Health.
  8. Folate (Folic Acid) — Vitamin B9. Harvard T.H. Chan School of Public Health. March 2023.
  9. Folic Acid Safety, Interactions, and Health Outcomes. Centers for Disease Control and Prevention. May 20, 2025.
  10. Too Much Folate in Pregnant Women Increases Risk for Autism, Study Suggests. Johns Hopkins Bloomberg School of Public Health. May 11, 2016.
  11. Schmidt RJ et al. Association of Maternal Prenatal Vitamin Use With Risk for Autism Spectrum Disorder Recurrence in Younger Siblings. JAMA Psychiatry. February 27, 2019.
  12. Hoxha B et al. Folic Acid and Autism: A Systematic Review of the Current State of Knowledge. Cells. August 3, 2021.
  13. Vasconcelos C et al. Folic Acid and Autism: Updated Evidences. Nutritional Neuroscience. July 5, 2024.
  14. MTHFR Gene Variant and Folic Acid Facts. Centers for Disease Control and Prevention. May 27, 2025.
  15. Hecker J et al. Adverse Effects of Excessive Folic Acid Consumption and Its Implications for Individuals With Methylenetetrahydrofolate Reductase C677T Genotype. Cureus. February 20, 2025.
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