Diet and Nutrition

The Sweet Spot on Folic Acid: Too Little Risks Baby’s Health, Too Much Increases Cancer Risk

About one in 33 babies is born with birth defects in the United States. Most women know that folic acid helps. When taken before and during early pregnancy, it can prevent from 50 to 70 percent of some types of birth defects of the brain and spine, according to the National Birth Defects Prevention Network (NBDPN).

Doctors regularly remind women of child-bearing age to get the recommended 400 mcg of folic acid per day. Scientists have confirmed the benefits so many times that most women planning families just accept they should be on supplements.

But then a small number of recent studies sent shockwaves through the health industry—high doses of folic acid were linked to an increased risk of cancer.

Could we be taking too much? If so, what are the risks to mom and baby?

Folic Acid is Good for Women’s Health

Folic acid (or “folate,” as it’s also called) is a form of a water-soluble B vitamin (B9). It occurs naturally in some foods like leafy green vegetables, fruits, beans, and meat.

Though we know this nutrient prevents birth defects, there is a lot more to it. It’s also important for cell production, brain health, and healthy DNA, and may benefit women in the following ways:

  • Builds blood cells: Folic acid is critical in the development of both white and red blood cells.
  • Supports a healthy heart: Folic acid and other B vitamins help break down homocysteine, which is an amino acid in blood. Those who are short on folic acid may end up with too much homocysteine in the body, which can increase risk of heart disease.
  • Keeps you smiling: If you’re feeling blue or depressed lately, it could be you’re not getting enough folic acid. A number of studies have linked folate deficiency to an increased risk of depression.
  • Maintains your thinking powers: According to the Mayo Clinic, those with low levels of folate in their blood may be more at risk for dementia or Alzheimer’s disease. Some studies have found that folic acid supplements can help improve cognitive performance in those who have low levels to begin with.
  • Keeps your cholesterol in check: Folic acid helps process and flush cholesterol from the body, so having enough may help keep cholesterol levels healthy.
  • Reduces risk of colon cancer: Folic acid works like a bodyguard in the blood—it helps protect DNA from cancer-causing substances. A 2011 study review, for example, that involved over 700,000 participants, found that higher intake of folate was associated with a reduced risk of colon cancer.
  • Protects your peepers: As we age, our eyes become more susceptible to diseases like age-related macular degeneration (AMD). Some scientists have found a link between that “homocysteine” we mentioned in the bullet on heart disease and AMD. Could folic acid help? A 2009 study found it may reduce risk, particularly in women vulnerable to cardiovascular disease.

Folic Acid Reduces Risk of Birth Defects

We have an overwhelming amount of research supporting the idea that folic acid helps keep babies healthy, and the studies just keep coming in.

“Birth defects drop 35% due to adding folic acid to flour,” read a January 15, 2015 headline in USA Today. The article was talking about a report from the CDC indicating that since we started adding folic acid to grains in 1998, we’ve prevented about 1,300 babies a year from being born with spina bifida and other related defects.

The key is to start taking the supplements before conception, as the vitamin has the biggest protective effect in the first four weeks. In fact, according to a 2014 study, starting folic acid before conception was critical for protection against birth defects.

Supplements Good for Moms, but Maybe Not Other Women

Considering that folic acid does all these great things for our health, should we all be taking supplements?

There have been concerns about that. What we’re learning is that on the whole, food is a much better source of nutrients than supplements are.

We’ve used “folic acid” and “folate” interchangeably so far in this article, but they’re actually two different things:

  1. Folate is found naturally in food.
  2. Folic acid is a synthesized (man-made) form of folate used in supplements.

Some studies have suggested that folic acid, the supplement form, could potentially cause some harm if we take too much—or at the very least, isn’t likely to protect us from disease.

You may have seen the articles over the last couple years bursting the bubble on supplements. Recent studies have shown that taking a multivitamin, for example, just doesn’t offer the health protection we thought it would.

The Annals of Internal Medicine published an editorial in December 2013 entitled “Enough is Enough: Stop Wasting Money on Vitamin and Mineral Supplements.” In it, the authors stated:

“In conclusion, beta-carotene, vitamin E, and possibly high doses of vitamin A supplements are harmful. Other antioxidants, folic acid and B vitamins, and multivitamin and mineral supplements are ineffective for preventing mortality or morbidity due to major chronic diseases.”

A 2013 report by the U.S. Preventive Services Task Force also threw cold water on the idea of supplements preventing disease. “Limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or CVD [cardiovascular disease],” researchers wrote.

Indeed, several studies examining folic acid and heart disease and stroke have found that supplementation did not reduce risk of heart attacks, strokes or other cardiovascular problems.

Could Too Much Folic Acid Increase Risk of Cancer?

There has also been some talk about too much folic acid increasing cancer risk.

In a recent 2014 animal study, for example, researchers found that taking large amounts (two-and-a-half times the daily requirement of 400 mcg) increased the risk of developing breast cancer.

An earlier 2006 study also found that high intake of folic acid increased risk of breast cancer in postmenopausal women, and a 2009 study found that high levels also increased risk of death from lung cancer.

Researchers have expressed concern that folic acid intake, on the whole, has increased over the past several years because of fortified foods.

Other studies, though, have found conflicting results. As noted above, one found that folic acid helped prevent colon cancer. In 2013, research involving over 50,000 participants found no significant cancer risks in those taking folic acid.

healthy food

What Health Experts Recommend Today

Despite what may seem like confusing information, women can be confident in taking certain steps to protect themselves and their children:

  • Women of childbearing age: If you’re planning a family, it’s still critical to be sure you’re getting enough folate. Take 400 mcg a day before getting pregnant and through the first trimester for the best result. Be sure to include fortified foods when figuring out how much you’re getting.
  • Look for 5-methylTHF or methyltetrahydrofolate: A recent 2013 study found that some women aren’t able to break down supplemental folic acid into its useful components as well as others. They may actually develop a build-up of “unmetabolized” or unused folic acid in their systems, which has been linked to an increase the risk of cancer. The more natural form, also called “5-methylTHF or methyltetrahydrofolate,” is more easily taken up by the body’s cells. Some supplement manufacturers now carry it—check the labels on your folic acid products.
  • All other women: If you’re not planning a family, or are past your child-rearing years, your best bet is to get your folate from foods rather than supplements. You’ll enjoy all the benefits with none of the risks. (No studies have linked folate from foods with cancer or any other health problems.)
  • Don’t take too much: If you’re low on folate (blood tests can show you), or you are concerned you may get pregnant and want to take supplements, you can feel perfectly safe doing so—just don’t take too much. Many foods are already fortified with folic acid, so you could be getting more than you think. Read labels. The National Institutes of Health’s Office of Dietary Supplements recommends no more than 1,000 micrograms of folic acid per day, but that should include food and fortified sources.

Below are some of the top-rated foods when it comes to folate content. All women can benefit from including more of these foods in their diets.

Natural Sources of Folate

  • Spinach, broccoli, and other green, leafy vegetables
  • Turnip greens
  • Bok Choy
  • Asparagus
  • Black eyed peas and other beans, including pinto beans, black beans, lima beans, and chickpeas
  • Lettuce
  • Avocado
  • Tropical fruits like mango, kiwi, papaya, pomegranate, guava, and banana
  • Orange juice
  • Wheat bread

Have you taken folic acid supplements in the past? Will you switch to food sources of the nutrient? Please share your thoughts.

Learn more about the importance of folic acid before pregnancy:


“National Birth Defects Prevention Month and Folic Acid Awareness Week—January 2015,” Centers for Disease Control and Prevention (CDC), January 16, 2015,

“Birth Defects Prevention Month 2015: Making Healthy Choices to Prevent Birth Defects—Make a PACT for Prevention,” National Birth Defects Prevention Network, January 2015,

“Folic Acid Awareness Week 2015,” NBDPN, January 2015,

Simon N. Young, “Folate and depression—a neglected problem,” J Psychiatry Neurosci., Mar 2007; 32(2):80-82,

Paul Y. Takahashi, “I’ve heard that folic acid supplements can improve cognitive function in older adults. Could those with Alzheimer’s disease also benefit from folic acid?” Mayo Clinic, June 4, 2014,

Dong-Hyun Kim, et al., “Pooled analyses of 13 prospective cohort studies on folate intake and colon cancer,” Cancer Causes Control., November 2010; 21(11):1919-1930,

Christen WG, et al., “Folic acid, pyridoxine, and cyanocobalamin combination treatment and age-related macular degeneration in women: the Women’s Antioxidant and Folic Acid Cardiovascular Study,” Arch Intern Med. February 23, 2009; 169(4):335-41,

Liz Szabo, “Birth defects drop 35% due to adding folic acid to flour,” USA Today, January 16, 2015,

VA Hodgetts, et al., “Effectiveness of folic acid supplementation in pregnancy on reducing the risk of small-for-gestational age neonates: a population study, systematic review and meta-analysis,” BJOG, November 26, 2014, DOI: 10.1111/1471-0528.13202,;jsessionid=13051F0DEFD537B0DC04BFEAA8D1DA87.f03t01.

Elisea Guallar, et al., “Enough is Enough: Stop Wasting Money on Vitamin and Mineral Supplements,” Annals of Internal Medicine, December 17, 2013; 159(12):850-851,

“Folic acid linked to breast cancer growth in animal study,” MedicalNewsToday, January 23, 2014,

Marta Ebbing, et al., “Cancer Incidence and Mortality After Treatment with Folic Acid and Vitamin B12,” JAMA, 2009; 302(19):2119-2126,

Rachael Z. Stolzenberg-Solomon, et al., “Folate intake, alcohol use, and postmenopausal breast cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial,” American Society for Clinical Nutrition, April 2006; 83(4):895-904,

Stein Emil Vollset, et al., “Effects of folic acid supplementation on overall and site-specific cancer incidence during randomized trials: meta-analyses of data on 50,000 individuals,” Lancet, March 2013; 381(9871):1029-1036,

“High doses of folic acid don’t raise cancer risk: study,” Reuters, January 27, 2013,

Stephen P. Fortmann, et al., “Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force,” Annals of Internal Medicine, December 17, 2013; 159(12):824-834,

Pietrzik K, et al., “Folic acid and L-5-methyltetrahydrofolate: comparison of clinical pharmacokinetics and pharmacodynamics,” Clin Pharmacokinet., August 2010; 49(8): 535-48,

Obeid R., et al., “Is 5-methyltetrahydrofolate an alternative to folic acid for the prevention of neural tube defects?” J Perinat Med., September 1, 2014; 41(5):469-83,

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Colleen M. Story

Colleen M. Story

Colleen M. Story is a novelist, health and wellness writer, and motivational speaker committed to helping people take control of their own health and well-being. She’s authored thousands of articles for a variety of health publications, and ghostwritten books for clients in the health and wellness industry. She is the founder of Writing and Wellness, a motivational site for writers and other creative artists. Find more at her website, or follow her on Twitter.