Folic acid and allergy: Study identifies ‘optimal’ level to reduce allergy risk

Infant blood levels of the B vitamin between 50 and 75 nanomoles per liter were associated with the least allergic sensitization in almost 500 children, according to results published in Allergy​.

Researchers at the University of Western Australia also report that, while high dose supplements during the third trimester of pregnancy were linked to eczema, no other allergic concerns were reported.

This is in contrast to other epidemiological studies, which suggested that folic acid supplements in late pregnancy may increase the infant’s risk of developing asthma (American Journal of Epidemiology​​, ​doi: 10.1093/aje/kwp315).

“In this population, the most significant source of folate intake in pregnancy was from specific folic acid supplements, and women taking more than 500 micrograms per day in this form were at the highest risk of delivering an allergic child, even after adjusting for maternal allergic status,”​ wrote the researchers.

“While the finding lends some support for epidemiological associations between maternal folate supplements in pregnancy and other allergic outcomes such as childhood asthma and wheezing, we did not see any effect on sensitization or wheezing ​per se.”​

Benefits for babies ​

An overwhelming body of evidence links has linked folate deficiency in early pregnancy to increased risk of neural tube defects (NTD) - most commonly spina bifida and anencephaly - in infants.

This connection led to the 1998 introduction of public health measures in the US and Canada, where all grain products are fortified with folic acid - the synthetic, bioavailable form of folate.

Preliminary evidence indicates that the measure is having an effect with a reported 15 to 50 per cent reduction in NTD incidence. A total of 51 countries now have some degree of mandatory fortification of flour with folic acid.

The US Centers for Disease Control and Prevention (CDC) recently listed the prevention of neural tube defects through flour fortification amongst its list of 10 great health achievements​ in the US for the last decade.

Study details​

The new study included 628 pregnant women in their last trimester of pregnancy. Blood samples were taken to measure folate levels in the infants and their mothers, while food frequency questionnaires were also provided to the mothers to assess intakes. The infants were followed for one year, and data was available for 484 children.

Results showed no differences in the blood levels in umbilical cords between infants who developed allergic disease (eczema) and non-allergic children.

Mothers who took over 500 micrograms per day of folic acid per day as a supplement were 85% more likely to have infants who developed eczema, than in women taking less than 200 micrograms per day.

“In this study, the most common manifestation of allergic disease in infants, eczema, was not associated with any significant differences in maternal or cord blood serum folate levels,”​ wrote the researchers.

“There were also no differences in the amounts of folate that mothers reported ingesting in their background diets. ​

“The only significant difference was that mothers of children with eczema appeared to consume more folate derived from supplements. However, this was only assessed in the third trimester and was not associated with any other allergic outcomes,”​ they added.

No changes​

“It is clearly premature to consider any change in practice which remains important to prevent neural tube defects. ​

“Together with these other studies, our findings strengthen the need to explore the potential mechanisms of interaction between ​in utero folate exposure and the developing immune system in humans.”​

assessed at 1 year, including sensitization.​Source: Allergy​
2012, Volume 67, Pages 50-57, doi: 10.1111/j.1398-9995.2011.02714.x
“The relationship between maternal folate status in pregnancy, cord blood folate levels, and allergic outcomes in early childhood”​​
Authors: J.A. Dunstan, C. West, S. McCarthy, J. Metcalfe, S. Meldrum, W.H. Oddy, M.K. Tulic, N. D’Vaz, S.L. Prescott