Vitamin D Level and Composite Indices of Femoral Neck Strength in a Group of Young Lebanese Men

Influence of Physical Activity Level on Composite Indices of Femoral Neck Strength in a Group of Young Overweight Men

The aim of the present study was to explore the influence of physical activity level on composite indices of femoral neck strength (compression strength index [CSI], bending strength index, and impact strength index) in a group of young overweight men. To do so, we compared composite indices of femoral neck strength in active overweight men and insufficiently active overweight men. They were divided into 2 groups based on their physical activity level: 70 active overweight men (engaging in more than 150 minutes of physical activity per week; 8.7 ± 4.8 h/wk) and 26 insufficiently active overweight men (engaging in less than 150 minutes of physical activity per week; 1.2 ± 0.7 h/wk). Height (m) and weight (kg) were measured, and body mass index (kg/m²) was calculated. Bone mineral density was measured by dual-energy X-ray absorptiometry at whole body, lumbar spine, total hip, and femoral neck. Body weight, lean mass, fat mass, and body mass index were not significantly different between the 2 groups. CSI, bending strength index, and impact strength index were significantly higher in active overweight men compared to insufficiently active overweight men. After adjustment for age, physical activity (h/wk) and lean mass, only CSI remained higher in active overweight men compared to insufficiently active overweight men. This study suggests that, in young overweight men, being active (engaging in more than 150 minutes of physical activity per week) is associated with greater composite indices of femoral neck strength. To our knowledge, this is the first study that finds a significant difference regarding composite indices of femoral neck strength between 2 groups of young overweight men with different levels of physical activity.

Positive Correlations Between Free Vitamin D and Bone Variables in a Group of Young Lebanese Women

Optimizing bone mass in adulthood is of great importance to prevent the occurrence of osteoporosis in later age. Vitamin D is an essential component of bone health. Low-serum vitamin D is associated with low bone mineral density (BMD), which is an important predictor of fracture risk. However, most cells, apart from renal tubular cells, are exposed to free rather than to total 25-hydroxyvitamin D. Whether free vitamin D would be a better marker than total vitamin D is still under debate. The aim of the present study was to explore the relationships between serum total vitamin D, vitamin D-binding protein (BP), free vitamin D, and bone parameters in a group of young Lebanese women. This study included 88 young female adults aged between 18 and 35 yr. Body composition and BMD were assessed by dual-energy X-ray absorptiometry, and the lumbar spine trabecular bone score was derived. Bone mineral content (BMC) and BMD were measured at the whole body (WB), the lumbar spine (L1-L4), the total hip (TH), and the femoral neck (FN). To evaluate hip bone geometry, dual-energy X-ray absorptiometry scans were analyzed at the FN, the intertrochanteric region, and the femoral shaft by the Hip Structure Analysis program. The cross-sectional area, the index of axial compression strength, and the section modulus (Z), as well as index of bending strength, were measured from bone mass profiles. Composite indices of FN strength (compressive strength index [CSI], bending strength index, and impact strength index [ISI]) were calculated as previously described. Direct measurement of free 25-hydroxyvitamin D concentrations was performed by immunoassay, which detects free vitamin D by ELISA on a microtiter plate. Serum vitamin D BP was measured using a Quantikine ELISA kit, which employed the quantitative sandwich enzyme immunoassay technique. Serum free vitamin D was positively correlated with WB BMC (r = 0.26, p < 0.05), WB BMD (r = 0.29, p < 0.05), L1-L4 BMD (r = 0.28, p < 0.05), TH BMD (r = 0.34, p < 0.01), FN BMD (r = 0.29, p < 0.05), CSI (r = 0.24, p < 0.05), and ISI (r = 0.28, p < 0.05). No positive correlations were detected between the total vitamin D level, the vitamin D BPs, and BMD. The positive associations between free vitamin D and several bone variables (WB BMC, WB BMD, L1-L4 BMD, TH BMD, FN BMD, CSI, bending strength index, and ISI) remained significant after adjustment for weight. In conclusion, the current study suggests that the free vitamin D serum level is a stronger positive determinant of bone parameters and hip bone strength indices in young female adults than total serum vitamin D.