Nwaru BI, et al. – The association between vitamin D intake during the first 4 years of life and asthma risk by age 5, was assessed in this study. There appeared an increased risk of childhood asthma, due to increased vitamin D intake in childhood, particularly intake at 1 and 2 years of age. This finding seemed to indicate a true effect or residual confounding by lifestyle or environmental factors. An evaluation of the longitudinal and age–dependent impact of vitamin D on the risk of asthma was permitted by repeated assessment of vitamin D intake.

Methods

• 182 incident asthma cases were matched to 728 controls on sex, genetic risk for type 1 diabetes, delivery hospital, and time of birth, within a Finnish population-based birth cohort.
• Age-specific 3-day food records appraised vitamin D intake.
• A validated version of the International Study of Asthma and Allergies in Childhood questionnaire was completed by parents at 5 years.

Results

• Supplements were the main source of vitamin D intake, at 3 months.
• Furthermore, intake from foods increased from 3 months on, mainly from fortified milk products.
• A link was observed between vitamin D intake at each specific age and an increased risk of any asthma, atopic and non-atopic asthma.
• However, only intake at 1 and 2 years was statistically significantly associated with asthma.
• Data highlighted an association of longitudinal vitamin D intake with an increased risk of asthma (OR 1.24; 95%CI 1.00-1.53).