25-Hydroxyvitamin D levels and its relation to muscle strength, maximal oxygen consumption, and body mass index in young and middle adulthood women.

Introduction: Vitamin D is a potent secosteroid hormone that provides many health benefits. The ubiquitous nature of vitamin D receptor (VDR) suggests widespread effect.

Purpose: The purpose of this study was to investigate the relationship between 25-hydroxyvitamin D (25OHD) levels and muscle strength, maximal oxygen consumption (VO2 max), and body mass index (BMI) in Iranian young and middle adulthood women.

Participants and methods: A cross-sectional descriptive study was conducted in 182 healthy Iranian women within the age range of 26-60 years. Body weight and height were measured, and BMI was calculated. VO2 max was determined by the Rockport test. Muscle strength was determined by the chest press, leg press, and hand grip test. Also, circulating levels of 25OHD were evaluated.

Results: Results showed a significant relationship between 25OHD levels and BMI, VO2 max, and muscle strength (chest press, leg press, hand grip dominant hand [HGDH], and hand grip nondominant hand [HGNDH]) in young and middle adulthood women (BMI in young and middle adulthood: r=-0.48, P <0.001 and r=-0.27, P =0.01, respectively; VO2 max in young and middle adulthood women: r=0.69, P <0.001 and r=0.57, P <0.001, respectively; chest press, leg press, HGDH, and HGNDH in young adulthood: r=0.58, r=0.59, r=0.65, and r=0.42, respectively, P <0.001; and in middle adulthood: r=0.73, r=0.34, r=0.66, and r=0.55, respectively, P ≤0.001). Multiple linear regression analysis showed that higher levels of VO2 max, HGDH, and chest press predicted higher 25OHD levels in the young adulthood women (R2 =0.75; β=0.39, β=0.35, and β=0.30, respectively; P <0.001). Moreover, VO2 max and HGDH were the strongest predictor of 25OHD levels in the middle adulthood women (R2 =0.71; β=0.35, β=0.40, respectively; P <0.001).

Conclusion: Based on the results, it could be concluded that VO2 max and strength are useful indirect marker for 25OHD levels in the young and middle adulthood women. It also seems that VO2 max and HGDH strength had stronger associations with 25OHD levels in the young adulthood women, and chest press and HGDH had stronger associations with 25OHD levels in the middle adulthood women.