Vitamin D Status And Muscular Strength In Youth: NHANES 2011-2014

Abstract

Vitamin D is a critical component of musculoskeletal health in youth. While several studies have established the importance of vitamin D for bone development, research specific to muscular strength is lacking. PURPOSE: To investigate the association between serum 25-hydroxyvitamin D (25OHD) status and muscular strength in a nationally-representative sample of U.S. youth. METHODS: The analysis included 1,706 boys and 1,644 girls from the National Health and Nutrition Examination Survey 2011-2014 between 6-18.9 years. Status of 25OHD was defined as: severe/deficient ≤ 37.5 nmol/L, insufficient > 37.5 to < 50 nmol/L, and sufficient ≥ 50 nmol/L. Muscular strength was assessed via handgrip and expressed as age- and sex-specific percentiles of relative strength (kg strength/kg body mass). General linear models were used to quantify differences in strength percentile by 25OHD status. Logistic models were used to compare the odds of low strength (< 25th percentile) between 25OHD groups. All analyses were stratified by sex while controlling for age, calcium intake, socio-economic status, race/ethnicity, physical activity, body mass index, and season of testing. RESULTS: Boys with sufficient 25OHD had a higher mean (SE) relative strength percentile than those in the insufficient or severe/deficient groups, 49.1 (1.8), 43.5 (2.2), and 40.7 (2.9), respectively (p < 0.05). Relative strength percentile was also highest for girls with sufficient 25OHD compared to the insufficient or severe/deficient groups, 51.8 (1.9), 45.6 (2.4), and 41.1 (3.3), respectively (p < 0.05). Further, boys in the insufficient group had a higher odds of low strength than 25OHD sufficient boys (odds ratio, OR = 1.8, 95%CI 1.1 to 3.0). Both girls in the insufficient and severe/deficient groups were more likely to have low strength compared to those with sufficient 25OHD, OR = 1.8 (1.1 to 2.8) and 3.3 (1.8 to 5.9), respectively. CONCLUSIONS: Youth with less than sufficient levels of 25OHD were consistently found to have lower relative handgrip strength and were more likely to have strength values below the 25th percentile. These findings underscore the importance of vitamin D for muscular strength in youth and future prospective studies to elucidate the mechanisms would be of benefit.