“Diet is a crucial environmental factor in early life that impacts the development of allergic diseases,” explains Nianhong Yang, MD. “However, research regarding the relationship between diet diversity during the complementary foods period—the period between exclusive breastfeeding and the introduction of regular foods— and allergic diseases is inconsistent. It has been suggested that early exposure to food antigens may have an adverse effect on the immune systems of infants and thus increase the likelihood of subsequent allergic diseases. Therefore, avoidance of allergenic foods was typically recommended as a prevention strategy. But recent evidence supports the hypothesis that reduced food diversity will impair normal development of the immune system and increase allergy risk, so the current paradigm is shifting from avoidance to controlled exposure. More evidence, however, is needed to optimize infant feeding regimes during the complementary food period.”

For a paper published in Pediatric Allergy and Immunology, Dr. Nianhong and colleagues sought to determine the association of food diversity in the first year of life with allergic outcomes in the second year.

Allergic Disease Reported in 6% of Infants

A total of 2,251 mother-infant pairs from Tongji Maternal and Child Health Cohort (TMCHC) were included in the study. Information about complementary foods introduction was gathered by telephone interview at 6- and 12-month postpartum follow-up. Any doctor-diagnosed allergic diseases during the second year were documented at the 2-year postpartum follow-up; food allergies in infancy were evaluated and self-reported by mothers at each postpartum follow-up. Multivariable logistic regression was used to assess the impact of food diversity at 6 and 12 months of age on later allergic diseases and food allergy.

Allergic diseases were reported in 135 infants (6.0%) between the ages of 1 and 2. Independent of food allergy history of infants and other potential confounders, the study team found that less food diversity at 6 months was associated with greater risk for subsequent allergic diseases. By 12 months, significant inverse associations with later allergic diseases and food allergy were detected. Children with increased food diversity in both periods had the lowest risk for allergic diseases during the second year of life.

Certain Foods Protective Against Allergy Risk

Introducing three or more food groups by 6 months of age and eight or more food groups by 12 months of age was associated with reduced risk of allergic diseases, the researchers found (Table). “Infants with lower diversity foods in any period had an increased risk for later allergic diseases, including allergic diseases involving both the respiratory tract and the skin,” Dr. Yang notes.

“Almost all of the infants were introduced to cereals, vegetables, fruits, and meats during the first year of life,” Dr. Yang says. “Compared with infants receiving eight or more food items, those received six or less food items were less likely to be introduced to fish and seafood, eggs, beans, nuts, cow’s milk and other milk products, and sweets in the complementary feeding period. But we discovered that introducing eggs or beans during the complementary feeding period had a protective effect against allergy risk.”

The researchers point out that the study had some limitations. “We did not measure the gut microbiome of the infants in the study, which limits the assessment of the potential modification effects of food diversity on the development of allergic diseases by microbial factors,” Dr. Yang notes. Another limitation is that the definition of allergic diseases based on the reported doctor’s diagnosis by mothers may result in an underestimation of the prevalence, which may weaken the relationship of the diversity of food with allergic diseases; however, a significant association was still found.

Dr. Yang and colleagues would like to see future studies further examine this topic. “We would like to see further investigations explore the optimal time for introducing some specific foods such as eggs, meat, or beans,” she says.