Total consumption of fruits and vegetables is not associated with the risk of asthma in children by age 5 years, according to a study in Pediatric Allergy and Immunology. Weak, inverse associations were seen between total consumption of leafy vegetables and asthma risk, and unprocessed vegetable consumption and nonatopic asthma risk.
Investigators used data from the Type 1 Diabetes Prediction and Prevention (DIPP) Nutrition Study to assess whether longitudinally and quantitatively measured consumption of fruits and vegetables is related to the risk of asthma in childhood.
All participants were born between 1996 and 2004 in Finland. The children who were still participating in the DIPP Nutrition Study at age 5 years were invited to participate in the DIPP Allergy Study.
The children’s food consumption data were evaluated in 3-day food records, which were completed at ages 3 and 6 months and at 1 through 5 years. The parents also completed an International Study on Asthma and Allergy in Childhood (ISAAC)-based questionnaire on allergic diseases and asthma in the child and family.
The main outcome was parentally reported asthma diagnosed by a physician and either wheezing symptoms or use of asthma medication within the previous 12 months, according to the modified ISAAC questionnaire. We recommend the future studies to further adjust for longitudinally measured dietary confounders such as fiber intake using appropriate statistical approaches to increase the understanding about the effect of processing of fruits and vegetables on the development of asthma.
The allergy study included 3053 children (52% male), of whom 184 (63% male) developed asthma. Of those children who developed asthma, 101 (55%) had atopic asthma, 75 (41%) had nonatopic asthma, and 8 (4%) could not be categorized. The mean (SD) overall follow-up was 4.8 (0.7) years, and the mean follow-up was 2.5 (1.1) years in children with asthma.
Total consumption of fruits and vegetables was not associated with the risk of asthma in the energy-adjusted model or after additional adjustment for sex, cow’s milk allergy, atopic eczema by age 6 months, gestation duration, and maternal and paternal asthma or allergic rhinitis (hazard ratio [HR], 1.00; 95% CI, 1.00-1.01 per consumption of 1 g/MJ).
A weak inverse association was found between consumption of leafy vegetables and asthma (adjusted HR, 0.87; 95% CI, 0.77-0.99), although this association occurred only after addition of baseline covariates in the model. No other individual vegetable or fruit subgroup was associated with asthma.
Overall, no associations were found between asthma risk and the consumption of fruits and vegetables when atopic and nonatopic asthma were analyzed separately. However, a weak, inverse association was observed with consumption of unprocessed vegetables (without potato) and the risk of nonatopic asthma (HR, 0.90; 95% CI, 0.81-0.98). Similar findings were observed after further adjustment with maternal age and education at delivery.
Among several limitations, children were included based on type 1 diabetes-associated class II HLA genotypes, which may limit the generalizability of the results to the general pediatric population. Also, the children were young with low overall fruit and vegetable consumption, and only mother’s age and education were included as socioeconomic covariates in the adjusted models.
“We recommend the future studies to further adjust for longitudinally measured dietary confounders such as fiber intake using appropriate statistical approaches to increase the understanding about the effect of processing of fruits and vegetables on the development of asthma,” stated the study authors. “High-quality information on childhood diet will be useful to guide future prevention studies.”
Metsälä J, Vuorinen A-L, Takkinen H-M, et al. Longitudinal consumption of fruits and vegetables and risk of asthma by 5 years of age. Pediatr Allergy Immunol. 2023;34(3):e13932. doi:10.1111/pai.13932