Effect of Food and Vitamin D Supplements on the Serum 25(OH)D₃ Concentration in Children during Winter Months.

Aim: To determine the contribution of food and vitamin D supplements on the serum 25-hydroxyvitamin D3 (25(OH)D3) concentration between October and April in a northern country (almost absent vitamin D synthesis by sunlight). Methods: Children aged 1–18 years were selected who visited the general pediatrician with a complaint whereby serum 25(OH)D3 concentration was determined. The intake of vitamin D was calculated based on a dietary questionnaire. Results: 51.1% of the 174 children had a serum 25(OH)D3 concentration below 50 nmol/L, 9.2% had a serum 25(OH)D3 concentration below 30 nmol/L. Adolescents showed lower concentrations compared to younger children. There was a positive correlation between the total amount of vitamin D obtained from food and the serum 25(OH)D3 concentration (r = 0.218, p = 0.004). The intake of milk contributed more to the serum 25(OH)D3 concentration compared to the intake of artificial supplementation, butter or fish. Conclusions: In the absence of vitamin D synthesis by sunlight, vitamin D obtained from food has a significant influence on the serum 25(OH)D3 concentration in children. Vitamin D supplements can be described as trivial. This means we should pay more attention to food as a natural source of vitamin D.