Get to Know Vitamin B9 (Folate/Folic Acid)

By Amy Campbell, MS, RD, LDN, CDCES | May 18, 2023

The next-to-last B vitamin in our review of the B complex family is vitamin B9. This vitamin has a different role than its other B complex cousins. To learn more, keep reading!

Vitamin B9 is perhaps more commonly known as folate or folic acid. What is the difference between folate and folic acid? Folate is the naturally occurring form of vitamin B9 in foods. When folate is added to foods and supplements, it's in the form of folic acid. Folic acid is actually better absorbed than folate in food.

Folate is needed to make DNA and RNA, according to the Office of Dietary Supplements (ODS) of the National Institutes of Health (NIH). This vitamin also plays a role in protein metabolism, and, along with vitamins B6 and B12, helps to break down homocysteine. Homocysteine is an amino acid that can be harmful in high amounts. For example, it's associated with heart disease. Here are some other functions of folate:

It's very important for pregnant women to get 600 micrograms (mcg) daily to reduce the risk of birth defects. Research indicates that women who take folic acid supplements before pregnancy and during the first trimester may reduce the risk of having a child with a neural tube defect by 72% to 100%.

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A meta-analysis of 30 randomized controlled trials showed that folic acid supplementation resulted in a 10% lower risk of stroke and a 4% lower risk of overall heart disease. The greatest benefit was seen in people who had lower blood levels of folate and who did not have heart disease.

Some observational studies show that people who get higher-than-average amounts of folate from food or folic acid from supplements for at least 15 years are more likely to have lower risks of colon cancer and breast cancer. Interestingly, a study published in 2007 indicated that folic acid fortification (meaning, folic acid added to foods) may have caused a small increase in the risk of colon cancer. But, as The Nutrition Source of the Harvard T.H. Chan School of Public Health writes, one explanation for this increase: a greater detection of existing tumors in the colon and rectum due to a wider use of colonoscopy. Overall, evidence shows a lower risk of colon and breast cancer with a greater intake of folate or folic acid.

Folate is found in a wide variety of foods. In 1998, the FDA started to require food manufacturers to add 140 micrograms (mcg) of folic acid per 100 grams to enriched breads, cereals, flours, pasta, rice, and other grain products to reduce the risk of neural tube defects. Doing so has helped increase the average folic acid intake by about 100 mcg/day.

Food sources of folate include:

Folic acid is found in multivitamins, prenatal vitamins, B complex supplements, and supplements that contain only folic acid. The ODS says that common doses range from 680 to 1360 mcg DFE (dietary folate equivalents) in supplements for adults and 340 to 680 mcg DFE in children's multivitamins.

The Recommended Daily Allowance for folate is as follows:

A deficiency of folate is rare because it's found in so many foods. Folate deficiency usually occurs along with other nutrient deficiencies due to a poor diet, alcoholism, and malabsorptive disorders.

People who are at risk for a folate deficiency are:

Folate toxicity from food sources is very rare. But, for folic acid (from supplements), the upper limit is 1,000 mcg for adults. This is because high amounts of folic acid, often taken to reverse anemia, can mask a vitamin B12 deficiency; a vitamin B12 deficiency can lead to permanent damage to of the brain, spinal cord, and nerves.

The amount of folic acid in typical multivitamin supplements is not high enough to cause harm.

Folic acid supplements can interact with several medication, says the ODS. Here are some examples:

Other drugs can be affected by folic acid. As a reminder, always let your provider know about any dietary supplements that you take.

The Mayo Clinic points out that folic acid supplements may cause:

Get to Know Vitamin A

Get to Know Vitamin B1

Get to Know Vitamin B2

Get to Know Vitamin B3

Get to Know Vitamin B5

Get to Know Vitamin B6

Get to Know Vitamin B7

Amy Campbell, MS, RD, LDN, CDCES on social media

A Registered Dietitian and Certified Diabetes Educator at Good Measures, LLC, where she is a CDE manager for a virtual diabetes program. Campbell is the author of Staying Healthy with Diabetes: Nutrition & Meal Planning, a co-author of 16 Myths of a Diabetic Diet, and has written for publications including Diabetes Self-Management, Diabetes Spectrum, Clinical Diabetes, the Diabetes Research & Wellness Foundation's newsletter, DiabeticConnect.com, and CDiabetes.com

Disclaimer of Medical Advice: Statements and opinions expressed on this Web site are those of the authors and not necessarily those of the publishers or advertisers. The information, which comes from qualified medical writers, does not constitute medical advice or recommendation of any kind, and you should not rely on any information contained in such posts or comments to replace consultations with your qualified health care professionals to meet your individual needs.

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