Serum 25-Hydroxyvitamin D is Associated With Bone Microarchitecture and Strength in a Multiracial Cohort of Young Adults

The Relationship between Bone Health Parameters, Vitamin D and Iron Status, and Dietary Calcium Intake in Young Males

Vitamin D, calcium, and iron are micronutrients crucial for bone health. However, their effect has been studied primarily in the cortical bone, with vitamin D status being assessed mainly from the total 25(OH)D serum fraction. The study aimed to investigate the impact of vitamin D (total and free fraction) and iron status (i.e., serum ferritin or soluble transferrin receptor) and calcium intake (ADOS-Ca questionnaire) on lumbar cortical and trabecular bone. In a cohort of 113 male subjects (76 athletes, 37 non-athletes) aged 15-19, the lumbar spine status (Z-score, bone mineral apparent density (BMAD), and trabecular bone score (TBS)) was determined using dual-energy X-ray absorptiometry (DXA). Relationships between the examined micronutrients and bone health parameters were observed only in athletes. Free 25(OH)D was significantly (p < 0.001) correlated with Z-score and BMAD, while total 25(OH)D (p < 0.001) and iron status (ferritin, Fe stores; p < 0.01) correlated solely with BMAD. Free 25(OH)D and ferritin concentrations were the best determinants of bone status (R2 = 0.330; p < 0.001) and explained 25% and 7% of the BMAD variance, respectively. No relationships were found between the micronutrients and TBS. The results confirmed the positive influence of vitamin D and iron on cortical, but not trabecular, bone status solely in physically active subjects. In athletes, free 25(OH)D seems to be a superior indicator of bone health to a total 25(OH)D fraction.

Male Runners With Lower Energy Availability Have Impaired Skeletal Integrity Compared to Nonathletes

CONTEXT

Female athletes, particularly runners, with insufficient caloric intake for their energy expenditure [low energy availability (EA) or relative energy deficiency] are at risk for impaired skeletal integrity. Data are lacking in male runners.

OBJECTIVE

To determine whether male runners at risk for energy deficit have impaired bone mineral density (BMD), microarchitecture, and estimated strength.

DESIGN

Cross-sectional.

SETTING

Clinical research center.

PARTICIPANTS

39 men (20 runners, 19 controls), ages 16-30 years.

MAIN OUTCOME MEASURES

Areal BMD (dual-energy x-ray absorptiometry); tibia and radius volumetric BMD and microarchitecture (high-resolution peripheral quantitative computed tomography); failure load (microfinite element analysis); serum testosterone, estradiol, leptin; energy availability.

RESULTS

Mean age (24.5 ± 3.8 y), lean mass, testosterone, and estradiol levels were similar; body mass index, percent fat mass, leptin, and lumbar spine BMD Z-score (-1.4 ± 0.8 vs -0.8 ± 0.8) lower (P < .05); and calcium intake and running mileage higher (P ≤ .01) in runners vs controls. Runners with EA

CONCLUSIONS

Despite weight-bearing activity, skeletal integrity is impaired in male runners with lower caloric intake relative to exercise energy expenditure, which may increase bone stress injury risk. Lower estradiol and lean mass are associated with lower tibial strength in runners.

Collapse

Key Words

• HR-pQCT
• athletes
• bone density
• energy availability

Collapse

MESH Headings

• Humans
• Male
• Female
• Leptin
• Cross-Sectional Studies
• Calcium
• Bone Density
• Absorptiometry, Photon
• Lumbar Vertebrae
• Testosterone
• Estradiol

Collapse

Grants

• K23 DK115903 NIDDK NIH HHS
• K24 HD071843 NICHD NIH HHS
• 1UL1TR002541-01 NIH HHS
• K24 HL092902 NHLBI NIH HHS
• Massachusetts General Hospital Executive Committee on Research
• National Institutes of Health
• Department of Defense Research Participation Program
• U.S. Army Research Institute of Environmental Medicine
• Oak Ridge Institute for Science and Education

Collapse

Affiliation(s) Collapse

Effect of vitamin D metabolites on bone histomorphometry in healthy black and white women: An attempt to unravel the so-called vitamin D paradox in blacks

An apparent vitamin D paradox, characterized by lower serum 25-hydroxyvitamin D (25(OH)D) levels and higher bone mineral density, is present in black population. In contrast, blacks have higher serum 1,25-dihydroxyvitamin D (1,25(OH)₂D) levels. The effect of 1,25(OH)₂D on the skeleton is not fully understood. We examined serum 25(OH)D, 1,25(OH)₂D and bone histomorphometry in 50 black and white women (25 each) matched for age, menstrual status, and BMI. Histomorphometric indices related to bone structure, remodeling and mineralization were measured in cancellous bone in iliac bone biopsies. Data analyses led to the following results: 1) serum 25(OH)D was significantly lower and 1,25(OH)₂D was significantly higher in black than in white women, but neither blacks nor whites revealed significant correlation between these two vitamin D metabolites. 2) there was no significant difference in PTH levels between blacks and whites. 3) except for greater trabecular thickness (Tb.Th) in blacks, there were no significant differences in other histomorphometric variables between the two ethnic groups. 4) osteoid surface (OS/BS), unlabeled osteoid surface (ulOS/BS), and osteoblast surface (ObS/BS) significantly correlated with serum 1,25(OH)₂D levels. We conclude that lower serum 25(OH)D levels in blacks do not impair bone structure and remodeling, nor decrease bone mineralization. Higher serum 1,25(OH)₂D levels in blacks may help preserve bone mass by stimulating bone formation via increasing osteoblast number and function, but moderately inhibit terminal bone mineralization as shown by higher ulOS/BS.