Allergic diseases are increasingly becoming a public health concern. The most common allergic diseases are asthma, allergic rhinitis (AR)/hay fever, eczema/atopic dermatitis (AD), and food allergies. According to the National Institute of Allergy and Infectious Diseases (NIAID), food allergies affect nearly 5% of children and 4% of adults in the US. Prenatal diet may be a critical and potentially modifiable factor in the prevention of offspring allergies. There are very few recommendations for dietary intake during pregnancy or lactation for allergy prevention globally, and the U.S. recommendations only refer to avoiding food allergens during pregnancy.

According to a review published in Nutrients, environmental triggers are considered major contributors to the increase in allergy prevalence for the last several decades, including nutritional status, farming conditions, and toxins from pollution and other chemicals in the modern environment, which are mediated by epigenetic mechanisms. Allergic diseases are caused by immune system hypersensitivity to these otherwise harmless environmental allergens. The authors note that the period between conception, pregnancy, and the first years of life “is considered the optimal time for environmental factors, such as nutrition, to exert their beneficial epigenetic effects.” In other words, what the mother consumes prior to conception and during pregnancy and lactation is a window of opportunity or susceptibility. 

A systematic review from the European Academy of Allergy and Clinical Immunology investigated the association between maternal diet during pregnancy and allergic outcomes (asthma/wheeze, food allergies, allergic sensitization, eczema/atopic dermatitis, allergic rhinitis, and seasonal allergies) in offspring. The results from 17 randomized controlled trials showed that prenatal vitamin D supplementation in doses higher than the recommended dietary allowances by most countries (600 IU/day for pregnant women) may have beneficial effects for the prevention of asthma in offspring. Based on the current study, vitamin D supplementation (in doses of 800 IU, 2,400 IU, or 4,000 IU) was associated with a reduced risk of asthma and wheezing. Of the 78 observational studies included in this review, the researchers found that a variety of nutrients, foods, and diet patterns (although heterogenous in doses) were associated with reduced incidence of allergic outcomes in offspring, including vitamins A, D, E, and C, copper, calcium, zinc, beta-carotene, magnesium, probiotic-containing foods, fish/fatty fish, and a Mediterranean-style diet. 

In another systematic review researchers assessed the effect of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation in pregnant and/or breastfeeding women on allergy outcomes in their children, including food allergy, eczema/atopic dermatitis, allergic rhinitis, and asthma. In the eight trials that were included with 3,366 women and their 3,175 children, women who supplemented with n-3 PUFA during pregnancy, lactation, or both showed a clear reduction in the primary outcome of any medically diagnosed immunoglobulin-E–mediated allergy in their children aged 12- to 36-months compared to a placebo. However, there were no clear differences seen beyond 36 months. There was a clear reduction in allergies for children in their first 12 months of life with n-3 PUFA, and there was a significant reduction in eczema, sensitization to eggs and to any allergens between 12 and 36 months of age, but no differences for hay fever or asthma were seen. 

It is clear that environmental factors (eg, dietary patterns, microbiome, pollutants) greatly influence immunometabolism and allergy in infants and children, and these factors are mediatated by epigenetic mechanisms. Although the evidence shows an association between reduced risk of allergies with vitamin D and n-3 PUFA consumption in pregnancy, there is a need for additional clinical studies beyond single nutrients to help inform nutritional guidelines for reducing allergic outcomes in infants and children.   

By Caitlin Higgins, MS, CNS