Seasonal, Age- and Sex-dependent Variations in Serum Vitamin D Concentrations in Children and Adolescents and their Relevance for Future Health

Abstract

Except for the first year of life, when infants are fully supplemented with 400 IU vitamin D, we found seasonal and age-dependent vitamin D distribution patterns for all age groups. The age groups between 2 and 9 years (grouped in 2-3, 4-5, 6-7, and 8-9 years) showed a positive deviation, and the age groups between 10-15 years showed a negative deviation from the mean curve over all age groups. The time frame between 10-15 years is associated with puberty, and the lower serum concentrations may indicate a higher conversion rate of 25(OH)-vitamin D into 1,25(OH)2 vitamin D. The pubertal decrease in serum vitamin D concentrations between boys and girls differs significantly in time, length, and magnitude. As puberty starts and ends earlier in girls than in boys, this difference may suggest that puberty is possibly among others a causal factor for the observed drop in serum vitamin D concentrations. Vitamin D deficiency especially in critical growth periods may hamper bone and immune health which has so far not been sufficiently considered. The dilemma of multiple factors and their influence on distribution curves can probably only be solved by using machine learning programs, which may be better suited to take multiple determinants into account to provide reliable data to achieve adequate Vitamin D supplementation. The associations among sunshine exposure, D supplementation and serum vitamin D concentrations are well known. Guidelines for dietary intake and serum concentrations are intended to limit the population risk of vitamin D deficiency. Present recommendations have been widely unsuccessful in achieving vitamin D sufficiency in childhood, adolescence and adulthood. Specific age-dependent seasonal D distribution curves do not exist, but they would allow an evidence-based estimate of vitamin D requirements for boys and girls in different stages of development. In a secondary analysis of the first wave (May 2003-May 2006) of the nationwide representative German KiGGS Study (Study on the Health of Children and Adolescents in Germany), we reanalysed data from 10,015 participants to investigate the seasonal variations in serum vitamin D concentrations for children and adolescents within two-year age intervals to increase our understanding of the relationship between serum vitamin D concentrations and child development in both sexes.