Folic acid in pregnancy increases allergies

Last Updated on June 5, 2019 by Afifah Hamilton
Read Time: 3 min

New study finds that unmetabolised artificial folic acid in pregnancy is linked to food allergies in offspring whilst levels of natural folate are not. This comes at a crucial time as the UK government considers mandatory folic acid fortification of UK flour. 

There has been an increase in childhood allergies over the last few decades and many explanations have been put forward including lack of exposure to protective bacteria during cesarian delivery through to lack of outdoor play (aka the hygiene hypothesis). A new study, however, has found that folic acid — given to women as a supplement during pregnancy — may be a contributing factor.

Molecular differences. Folic acid (top) is the artificial form of folate which is frequently found in supplements and fortified bread and cereals. Whilst it is effective in helping prevent neural tube defects there have long been concerns that unlike natural folate (below) it is not fully metabolised remaining in the blood for extended periods of time. Image: Linus Pauling Institute

The research was presented at the meeting of the American Academy of Allergy, Asthma & Infectious Disease (AAAAI) and the World Allergy Organization (WAO). The team from Johns Hopkins, Baltimore, used data from the Boston Birth Cohort which showed that at birth mean folate levels were lower and unmetabolised folic acid levels were higher among children that went on to develop allergies. One of the paper’s authors, Corinne Keet, MD, PhD, said:

“Food allergy prevalence seems to be increasing, and it has been hypothesized that increased [in utero] folic acid exposure may be a central contributor to this… When the synthetic form of folate is metabolized, only a certain amount is able to be processed through the normal pathways, and the excess circulates as unmetabolized folic acid.

The folate vs unmetabolised folic acid ratios were measured at birth with babies being categorised into quartiles. Children in the highest quartile of unmetabolised folate at birth went on to have almost ten times the incidence of childhood food allergies compared to those with the lowest levels.
Interestingly, there was no association with levels of folate or unmetabolised folic acid of the children during their early years indicating that the effect is taking place during pregnancy.

This research comes at a timely moment as the UK government appears set to mandate fortification of bread with folic acid in an attempt to reduce birth defects. Here are some of the recent headlines: (clicking will take you to the BBC article)

The argument that adding folic acid to staple foods like bread will reduce birth defects is compelling and looks likely to happen in the UK in the near future, but without the cautionary tale about the possible downsides of artificial folic acid this good deed may inadvertently contribute to an increase in food allergies. What is exasperating is that for a few pennies more, proper food grade folate could be used for any mandated fortification which would prevent the knock on effects from unmetabolised folic acid. As well as helping combat rising childhood allergies, natural folate would better help reduce the rate of neural tube defects as it would be fully metabolised.

As it stands NHS prescribed pregnancy vitamins continue to contain the cheaper folic acid rather than the food grade folate (L-methylfolate). If you or someone you know is either pregnant or hoping to conceive they should opt for a supplement containing methylfolate and avoid folic acid. This will give them the same protection but without the potential side effects associated with the artificial form.  Unhelpfully, both synthetic and natural forms get labelled Vitamin B9, folic acid or folate so careful checking of supplement fine print is vital. To be safe, choose products clearly labelled as methylfolate.

Increased childhood allergies are almost certainly not the only side effect of unmetabolised folic acid, yet if the mandate to add it to UK flour goes ahead most of the population will unwittingly become part of a large-scale experiment. Yet another reason not to eat grains.


Cytoplan’s Pregna-Plan is a pregnancy and pre-pregnancy supplement for women which contains the natural form of folate (L-methylfolate) along with other important vitamins and minerals necessary for healthy foetal development, including iodine and vitamin D3. At the time of writing they were offering 3 for the price of 2, with free shipping on orders over £25. Cytoplan are a great company, proudly British, started by nutrition scientists and practitioners and now run as a charitable organisation, providing supplements to the needy.

Check current offer price

Article source: MedpageToday, Folic Acid in Utero Tied to Food Allergy Risk, 06/03/18

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