Vitamin D Supplementation Has No Impact on Cardiorespiratory Fitness, but Improves Inflammatory Status in Vitamin D Deficient Young Men Engaged in Resistance Training

Abstract

Data on the effect of vitamin D (Vit-D) supplementation on cardiorespiratory fitness (VO2max) are conflicting. A possible source of discrepancies in the literature is the heterogeneity in baseline Vit-D status among participants in previous studies. The main objectives of the present study were to assess the impact of Vit-D supplementation on VO2max and inflammatory status in Vit-D deficient young healthy men. Participants (n = 39, baseline serum Vit-D level < 50 nmol/L) were quasi-randomly assigned to one of the two groups, which, in a double-blind manner, supplemented their diet daily with either Vit-D (8000 IU; VD) or placebo (PLC) and concomitantly performed a 12-week supervised resistance training program. During the 12-week intervention, serum Vit-D concentrations increased 3.9-fold (p < 0.001) in the VD group while no changes occurred in the PLC group. Baseline VO2max did not differ in the two groups and remained unchanged during the intervention. Serum interleukin-10/tumour necrosis factor alpha ratio increased significantly (30%, p = 0.007; effect size 0.399) in VD but not in PLC group. In conclusion, 12-week Vit-D supplementation increases serum 25(OH)D levels and improves inflammatory status, but has no impact on VO2max in Vit-D deficient young men engaged in resistance training.

Keywords: cytokines; low-grade inflammation; maximal oxygen consumption; vitamin D.

Figure 1

Serum 25(OH)D concentration (lines) and VO₂max (columns) during 12-week supplementation and resistance training period. Data are presented as mean ± SD; n = 17 in placebo and n = 20 in vitamin D group. W 0—W 12, weeks 0—12. Significantly different (p < 0.05): * from W 0; # from previous week; $ from placebo group.