title: Tibial bone responses to 6-month calcium and vitamin D supplementation in young male jockeys: A randomised controlled trial.
abstract: Young male jockeys compromise bone health by engaging in caloric restriction and high volumes of physical activity during periods of musculoskeletal growth and development. The aim of this randomised, double-blinded, placebo-controlled trial was to establish whether calcium and vitamin D supplementation would improve bone properties of young male jockeys. We conducted a 6-month trial with two groups of weight-, height- and age-matched apprentice male jockeys (age=20.2 ± 3.2 yrs). Participants were supplemented with 800 mg of calcium and 400 IU of vitamin D (S, n=8) or a placebo (cellulose) (P, n=9) daily for 6-months. Baseline calcium intake was (669.7 ± 274.3 (S) vs 790.4 ± 423.9 (P) and vitamin D 64.6 ± 19.5 (S) vs 81.2 ± 24.4 (P) with no statistical differences. Peripheral quantitative computed tomography (pQCT) measured ultra-distal (4%) and proximal (66%) tibial bone properties at baseline and 6 months. Blood-borne markers of bone turnover, P1NP and CTX and vitamin D concentration were assessed. After co-varying for height, weight and baseline bone measurements, the supplemented group displayed greater post-intervention bone properties at the 66% proximal site with cortical content (mgmm) 6.6% greater (p<0.001), cortical area (mm(2)) 5.9% larger (p<0.001), cortical density (mgcm(2)) 1.3% greater (p=0.001), and total area (mm(2)) 4% larger (p=0.003). No other between group differences in bone variables were observed. Blood analysis indicated higher vitamin D levels (18.1%, p=0.014) and lower CTx (ng/L) (-24.8%, p=0.011) in the supplemented group with no differences observed in P1NP. This is the first randomised controlled trial to examine the efficacy of calcium and vitamin D supplementation in improving bone properties in a highly vulnerable, young athletic, weight-restricted population. Results using pQCT indicate beneficial effects of supplementation on bone properties in as little as six months. Although the study size is small, this intervention appears promising as a strategy for improving bone health in young athletes in weight-restricted sports.
authors.affiliation: School of Exercise Science, Australian Catholic University, Australia. Electronic address: leslie.silk@acu.edu.au.
authors.forename: Leslie N
authors.initials: LN
authors.lastname: Silk
authors.affiliation: School of Exercise Science, Australian Catholic University, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Greene
authors.affiliation: School of Exercise Science, Australian Catholic University, Australia; The Boden Institute Of Obesity, Nutrition, Exercise & Eating Disorders, The University of Sydney, Australia.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Baker
authors.affiliation: School of Exercise Science, Australian Catholic University, Australia.
authors.forename: Caron B
authors.initials: CB
authors.lastname: Jander
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D056352:Athletes; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000187:drug effects; D016723:Bone Remodeling / Q000187:drug effects; D002136:Calcium, Dietary / Q000008:administration & dosage*; D031204:Caloric Restriction / Q000009:adverse effects; D024042:Collagen Type I / Q000097:blood; D019587:Dietary Supplements; D004311:Double-Blind Method; D006736:Horses; D006801:Humans; D008297:Male; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000097:blood; D011347:Procollagen / Q000097:blood; D013177:Sports; D013977:Tibia / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D014807:Vitamin D / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002136:Calcium, Dietary; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C047202:procollagen Type I N-terminal peptide; D014807:Vitamin D
keywords: Calcium; Cortical bone; Peripheral QCT; Supplementation; Young males