title: Plasma 25-hydroxyvitamin D, more so than its epimer, has a linear relationship to leaner body composition across infancy in healthy term infants.
abstract: Vitamin D status positively associates with skeletal muscle mass and function in adolescents. The C-3 alpha epimer of 25-hydroxyvitamin D3 (3-epi-25(OH)D3) is high in infants, yet the potential impacts of 25-hydroxyvitamin D3 (25(OH)D3) and 3-epi-25(OH)D3 on skeletal muscle development are largely unexplored. The objective of this study was (i) to explore how the concentrations of 25(OH)D3 and 3-epi-25(OH)D3 track with body composition (lean mass (LM) and fat mass (FM)) and (ii) to determine the association between 25(OH)D3 and 3-epi-25(OH)D3 in infancy. Healthy breastfed infants (n = 132) were followed from 1 to 12 months of age as part of a vitamin D dose-response study (NCT00381914). Anthropometry and diet were assessed. Body composition was measured with dual-energy X-ray absorptiometry. Plasma 25(OH)D3 and 3-epi-25(OH)D3 concentrations were evaluated using liquid chromatography tandem mass spectrometry. Plasma 25(OH)D3 and 3-epi-25(OH)D3 increased from 1 to 3 months of age and decreased thereafter (p < 0.05). Infants with 25(OH)D3 concentrations above 75 nmol/L did not have a higher LM (g or %; p > 0.273) than those below this cutoff. LM was not associated with 25(OH)D3, whereas LM% was positively associated with 25(OH)D3 (β = 0.03; CI: 0.01 to 0.06; p = 0.006), while accounting for sex, weight-for-age Z-score, protein and fat intake, and age. For FM, the variables accounting for a significant amount of the variation were plasma 25(OH)D3 concentration (β = -2.38; CI: -4.35, -0.41; p = 0.019), weight-for-age Z-score, protein and fat intake, and time. In healthy infants, higher vitamin D status associates with leaner body composition, though the effect is smaller in magnitude relative to growth.
authors.affiliation: a Department of Kinesiology and Physical Education, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada.
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Hazell
authors.forename: Sina
authors.initials: S
authors.lastname: Gallo
authors.forename: Ilze
authors.initials: I
authors.lastname: Berzina
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Vanstone
authors.forename: Celia
authors.initials: C
authors.lastname: Rodd
authors.forename: Hope A
authors.initials: HA
authors.lastname: Weiler
mesh_terms: D001823:Body Composition; D002117:Calcitriol / Q000097:blood*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D013851:Thinness / Q000097:blood*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002117:Calcitriol
keywords: C-3 alpha epimer of 25-hydroxyvitamin D3; body composition; composition corporelle; infancy; première enfance; épimère alpha C-3 de la 25-hydroxyvitamine D3