Taking too much folic acid during pregnancy is risky

If you’re pregnant or thinking about getting pregnant, you’ve no doubt heard that you should be taking folic acid. That’s because it’s long been established that women who take folic acid supplements before getting pregnant and during pregnancy have a significantly lower chance of having a baby with neural tube defects like spina bifida.

However, recent research suggests that when it comes to folic acid, it may be possible to have too much of a good thing.

What is folic acid?

Folic acid is the synthetic form of the B vitamin folate. Folate is naturally found in leafy greens, like spinach and kale, pulses, kidney beans and lentils, and fruits like oranges, grapefruit and avocados. But not everyone gets enough folate naturally in their diet.

Because neural tube defects happen early in pregnancy—before many women even know they are pregnant—and because pregnancies are often unplanned, Health Canada recommends that all women who could become pregnant take a multivitamin containing 0.4 mg of folic acid daily. If you’re planning to become pregnant, it’s recommended you take the supplement for at least three months beforehand. The recommended intake then increases to 0.6 mg during pregnancy.

How much folic acid is too much?

While there is no concern about consuming too much folate—you really can’t overdo eating lentils and spinach—there are growing concerns over the possible effects of too much folic acid. A supplement containing 0.4 mg of folic acid plus a number of servings of folate-rich food each day is enough to meet the daily folic acid/folate recommendation of 0.6 mg during pregnancy. But many women are consuming far more than that. For one thing, most prenatal supplements contain 1 mg of folic acid, which on its own is much higher than the recommended amount, and is actually the safe upper limit (also known as the Tolerable Upper Intake) of folic acid.

But Health Canada also requires foods like white flour, enriched pasta, and cornmeal to be fortified with folic acid. Manufacturers of many other foods, like plant-based beverages, such as soy, rice and almond milk, various breakfast cereals, goat’s milk and pre-cooked rice, voluntarily fortify with folic acid. Even the newly popular nutritional yeast is often fortified with significant amounts of folic acid.

What’s the problem with too much folic acid?

But even though folic acid is important, taking too much could be problematic. Research is pointing to some possible negative effects of consuming too much folic acid, such as impaired fetal growth, increased risks of childhood diseases like asthma and autism, and promoting the growth of some cancer cells. It’s important to note that the studies showing cause and effect of too much folic acid have been carried out in animals. Those involving humans have only been observational, meaning other factors could play a role in these links. (Doing controlled, or clinical, studies, where women are given more folic acid to see the effects, would be unethical.)

As concerns about excess folic acid were growing, a workshop on the issue, which included stakeholders from academia, industry, government, and health professional groups was held in Ottawa in November 2017. The workshop conclusions were published in the American Journal of Clinical Nutrition in December 2018.

While it’s unclear exactly how too much folic acid may be harmful, it may involve epigenetics, or the turning on and off of different genes in the fetus, which may play a role in the development of disease later in life.

Some women who are at a higher risk of having a baby with neural tube defects are advised to take higher dosages under the care of their physician, but for most women, there isn’t a benefit to taking more than the recommended dose of folic acid. “If there is no benefit of higher intakes, then there is likely only risk,” says Deborah O’Connor, a professor in the department of nutritional sciences at the University of Toronto and a co-author of the published paper.

Is anyone doing anything about too much folic acid?

One major concern noted in the report is the lack of availability of prenatal supplements containing the recommended 0.4 mg of folic acid.

Healthcare providers usually prescribe what’s generally available in the marketplace, and most prenatal supplements have 1 mg of folic acid. Insurance companies reimburse for prescribed supplements only, so women will typically stick to what her healthcare provider prescribes.

In addition, the paper noted that individual companies are reluctant to reduce the folic acid dose in their prenatal supplements because it may put them at a competitive disadvantage if they are not comparable with other products.

But change may be happening. As a result of the workshop, major educational initiatives by physicians and dietitians to increase awareness about the discrepancy between folic acid recommendations and supplement dosages are now underway across the country.

Nestlé has also recently reduced the amount of folic acid in their Materna supplement from 1 mg to 0.6 mg. Bénédicte Fontaine-Bisson, an associate professor in the school of nutrition sciences at the University of Ottawa and another co-author of the workshop summary, says this is encouraging. “They are the number one seller of prenatal supplements in Canada, so this will have a direct impact on folic acid intake of thousands of Canadian women across the country.” She also points to the company posting the guidelines for prenatal intake of folic acid on their website to inform the general public as a step in the right direction. The new formulation is already in stores across the country.

However, when asked whether they had any plans to change the formulation for Centrum Prenatal with its 1 mg folic acid, a GSK Consumer Healthcare spokesperson said they “continuously review the emerging science on all micronutrients, including folic acid, along with professional recommendations and take this into account when looking at developing new formulas. Our formulas are authorized by Health Canada and are within Health Canada guidelines. They are safe and effective when used as directed.”

In the meantime, it’s up to you to let your healthcare provider know you want a prenatal supplement with a lower dose of folic acid.  At the same time, while taking your prenatal supplement, choose more folate-rich foods and lessen the amount of folic acid you’re consuming from food. Opt for whole grain products over white flour selections and look for folic acid on ingredient labels to reduce the amount in your diet.

“We need to get back to the recommended folic acid dose,” says O’Connor.

Rosie Schwartz is a Toronto-based consulting dietitian and the author of  The Enlightened Eater's Whole Foods Guide (Viking Canada). 

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