Lean body mass accretion is elevated in response to dietary vitamin D: A dose-response study in female weanling rats.

Vitamin D status positively relates to lean body mass in infants. This study tested the effect of vitamin D on body composition and growth-related hormones. It was hypothesized that low vitamin D status programs for higher fat mass accretion. Female weanling Sprague-Dawley rats (4 weeks; n = 6/diet) were randomized to AIN-93G diets with modified vitamin D contents for 8 weeks: group 1 (1 IU vitamin D3/g diet), group 2 (2 IU vitamin D3/g diet), and group 3 (4 IU vitamin D3/g diet). At week 0, 4, and 8 of study, measurements included: serum 25(OH)D3, IGF-1, IGFBP3, leptin, and whole body composition assessed with DXA. Differences among groups were tested using mixed model ANOVA with Tukey's post hoc t-tests. No differences were observed in baseline body composition and biomarkers, nor did body weight and food intake differ over the study. At week 8, serum 25(OH)D3 in group 3 was higher (P < .0001) compared to groups 1 and 2. At 8 weeks, lean mass (P < .05) and lean mass accretion (P < .05) were significantly higher in groups 2 and 3 compared to group 1. Serum IGF-1 concentration declined over time (P < .001) with smaller declines at week 8 in group 3 (P < .05). Serum IGFBP3 concentration was lower at week 4 in group 2 compared to groups 1 and 3. Serum leptin concentration and fat mass were not affected by diet. These results suggested that the achievement of higher vitamin D status may support a lean body phenotype without altering weight gain.