Bone Abstracts

Objectives: Young male jockeys undertake calorie restriction and high volumes of physical activity during periods of musculoskeletal growth and development. Previous research shows that jockeys have compromised bone health^1–4 and display disordered eating^5–7. Restricted intakes of calcium and vitamin D, together with excessive amounts of exercise, increase the risk of osteoporosis in males⁸. The aim of this study was to establish whether calcium and vitamin D supplementation would improve bone properties of young male jockeys.

Methods: We conducted a 6-month, randomised, double-blinded placebo-controlled trial with two groups of weight-, height- and age-matched apprentice male jockeys (age=20.18±3.23 years). Participants were supplemented with 800 mg of calcium and 400 IU of vitamin D (n=8) or a placebo (n=9) daily for 6-months. pQCT measured 4 and 66% distal tibia and distal radius bone properties at baseline and 6 months. Blood-borne markers of bone turnover, P1NP and CTX and vitamin D status were assessed.

Results: After co-varying for height, weight and baseline bone measurements, the supplemented group displayed greater post-intervention bone density at both the radius and tibia. At the tibia, greater bone density at the 66% proximal site for the supplemented group were observed in cortical content (mg×mm) (P=0.000, partial η²=0.701), cortical density (mg×cm²) (P=0.001, partial η²=0.592), total area (mm²) (P=0.003, partial η²=0.526) and cortical area (mm²) (P=0.000, partial η²=0.691). At the radius, greater trabecular area (mm²) (P=0.028, partial η²=0.341) and cortical area (mm²) 66% proximal site (P=0.003, partial η²=0.541) were found in the supplemented group. No other between group differences were observed. Blood analysis indicated greater vitamin D (nmol/l) (P=0.014, partial η²=0.384) and CTx (ng/l) (P=0.011, partial η²=0.400) in the supplemented group.

Conclusions: 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 indicate the beneficial effects of supplementation on bone properties in as little as 6 months. Whilst the study size is small, this intervention appears promising as a strategy for improving bone health in young athletes in weight-restricted sports.

References

1. Dolan E, et al. Weight regulation and bone mass: a comparison between professional jockeys, elite amateur boxers, and age, gender and BMI matched controls. Journal of Bone and Mineral Metabolism 2012 30 (2) 164–170.

2. Dolan E, et al. An altered hormonal profile and elevated rate of bone loss are associated with low bone mass in professional horse-racing jockeys. Journal of Bone and Mineral Metabolism 2012 30 (5) 534–542.

3. Greene DA, et al. Bone health of apprentice jockeys using peripheral quantitative computed tomography. Int J Sports Med 2013 34 (EFirst) 688–694.

4. Waldron-Lynch F, et al. High bone turnover in Irish professional jockeys. Osteoporosis International 2010 21 (3) 521–525.

5. Cotugna N, Snider OS & Windish J. Nutrition assessment of horse-racing athletes. Journal of Community Health 2011 36 (2) 261–264.

6. Dolan E, et al. Nutritional, lifestyle, and weight control practices of professional jockeys. Journal of Sports Sciences 2011 29 (8) 791–799.

7. Leydon M & Wall C. New Zealand Jockeys’ dietary habits and their potential impact on health. Int J Sport Nutr Exerc Metab 2002 12 (2) 220–237.

8. Ebeling PR. Osteoporosis in men. New England Journal of Medicine 2008 358 (14) 1474–1482.

Disclosure: The authors declared no competing interests.