Ancestry Is a Key Determinant Of Vitamin D Status In Children With Demyelination

Background: In a population of young healthy Canadians, we observed that ancestry is a key determinant of vitamin D status (serum 25(OH)D levels), independent of skin pigmentation (melanin) and vitamin D supplementation. Amongst Canadian children with acquired demyelinating syndromes (ADS), those with lower serum 25(OH)D concentrations at ADS presentation have increased risk of multiple sclerosis (MS).

Objectives: We sought to evaluate predictors of 25(OH)D levels in a pilot subgroup of Canadian children with ADS.

Methods: We evaluated relationships between serum 25(OH)D levels and vitamin D supplement use, season (“summer” vs. “other”), skin pigmentation (DSM II Colormeter - melanin units), and self-reported ancestry (“European” vs “non-European”).

Results: We studied 38 children enrolled consecutively from a single centre participating in a national longitudinal study of pediatric ADS. Participants were evaluated a median [interquartile range (IQR)] time of 2.1 (1.0-5.1) years after ADS onset at a mean (SD) age of 11.9 (4.8) years; 20 (53%) were female and 11 (23%) have been diagnosed with confirmed MS. Median (IQR) 25(OH)D level was 83 (68-105) nmol/L and 81% reported consuming oral vitamin D supplements at time of serum procurement. 25(OH)D did not differ between those reporting taking vitamin D supplements vs. those who did not (p=0.64) nor between summer vs. other seasons (p=0.14) . Although melanin did not correlate with 25(OH)D levels (p=0.06), 25(OH)D was higher in those of European ancestry as compared to non-Europeans (99 (75-109) nmol/L vs. 77 (55-101) nmol/L [median (IQR)]; p=0.01) and melanin was lower in the European ancestry group (p<0.001). Use of vitamin D supplements did not differ between these groups (p=0.29).

Conclusions: In a pilot group of children with ADS, cross-sectional 25(OH)D was not independently related to reported vitamin D supplement use, season, or melanin. Vitamin D supplementation is routinely recommended to these patients; thus higher 25(OH)D levels and more frequent use of vitamin D supplements were observed in this cohort than in the general Canadian pediatric population. Children of European ancestry had higher 25(OH)D as compared to non-European ancestries despite no reported difference in compliance with vitamin D supplementation. Various facets pertaining to ancestry may affect vitamin D status beyond skin pigmentation, such as diet, sun exposure, or genetic differences in vitamin D metabolism.