This site uses cookies to store information on your computer. Learn more x


Providing perspectives on recent research into vitamins and nutritionals


Folic Acid Intake, Blood Levels during Pregnancy and Newborn Health

By Manfred Eggersdorfer & Michael McBurney

Researchers from Johns Hopkins University highlight the importance of maintaining normal blood levels of B vitamins in pregnant women. 25 years ago, a Lancet publication established that folic acid supplementation would prevent neural tube defects (NTDs). This was the conclusion from a randomized control trial (RCT) conducted at 33 centers in 7 countries.

According to the ABCnews, a new epidemiological study finds high levels of folic acid in the blood of pregnant women may not be good for babies. Taking 400 µg folic acid per day raises folic acid concentrations to ~35 nmol/L. In the Johns Hopkins study, the scientists reported folic acid concentrations in a part of the women with levels up to 59 nmol/L. Johns Hopkins’ researchers state they don’t know exactly why some of the women had such high levels in their blood.

Red blood cell folate concentrations are a better indicator of long-term folate status because serum/plasma concentrations are constantly changing. Maybe the women participating in the Johns Hopkins study were not fasted. At this time, we do not know.

It is known that the US Preventive Services Task Force (USPSTF) concluded (May, 2016) with high certainty (A) that all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 µg) of folic acid. They concluded there is “adequate evidence that the harms to the mother or infant from folic acid supplementation taken at the usual doses are no greater than small.

As written by the lead author of the Lancet RCT study testing folic acid supplementation wrote, Dr Nicholas Wald, “Not fortifying with folic acid, despite repeated evidence that it is safe and cost-effective public health strategy, is like having the polio vaccine and refusing to use it.”

According to the WHO, the threshold for lowest risk of neural tube defects is achieved by maintaining  plasma folate >15.9 nmol/L (7 ng/mL) or red blood cell folate >906 nmol/L (400 ng/mL). More research is needed to determine optimal upper levels.

Main Citation

Draft Recommendation Statement: Folic Acid for the Prevention of Neural tube Defects: Preventive Medication. U.S. Preventive Services Task Force. May 2016

Other Citations

Prevention of neural tube defects: Results of the Medical Research Council Vitamin Study. 1991 Lancet 338:131-137

Lamers Y, Prinz-Langenohl R, Moser R, Pietrzik K. Supplementation with [6S]-5-methyltetrahydrofolate or folic acid equally reduces plasma total homocysteine concentrations in healthy women. 2004 Am J Clin Nutr 79:473-478

World Health Organization. Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects. Guideline. 2015 ISBN 978 92 4 154904 2

Prinz-Langenohl R, Bramswig S, Tobolski O, Smulders YM, Smith DE, Finglas PM, Pietrzik K. [6S]-5-methyletetrahydrofolate increases plasma folate more effectively than folic acid in women with the homozygous or wild-type 677àT polymorphism of methylenetetrahydrofolate reductase. 2009 Br J Pharmacol doi: 10.1111/j.1476-5381.2009.00492.x