Selenium is an essential trace element with roles in musculoskeletal health(Reference Moreno-Reyes1,Reference Zhang2) . Osteoclast inactivation is associated with selenium supplementation in vitro and selenium status is correlated negatively with markers of bone health(Reference Hoeg3,Reference Beukhof4) . However, the impact of selenium supplementation on bone turnover markers (BTM) has not been studied. This study investigated the effects of selenium supplementation for up to 5 years in older people on BTM including osteocalcin, procollagen type 1 N-terminal propeptide (P1NP), carboxy-terminal collagen crosslinks and bone alkaline phosphatase.
490 Danish men and women (60–74 y) were randomised to receive 0, 100, 200 or 300 μg of selenium daily as selenium-enriched yeast. Plasma selenium concentration was measured using inductively-coupled-plasma mass spectrometry and BTMs were measured using an autoanalyser at baseline, 6 months and 5 years in non-fasted samples. Data were analysed by ANCOVA with polynomial contrasts to investigate the shape of the dose-response relationships. Covariates included: age, body mass index, baseline plasma selenium concentration, baseline BTM, smoking, alcohol, supplement use and medication.
Plasma selenium concentration increased significantly with increasing selenium supplementation at 6 months (84.1, 155.2, 212.3, 258.3 ng/ml for placebo, 100, 200 and 300 μg selenium, respectively) (P < 0.001) and remained elevated at 5 years (88.2, 156.4, 223.8 and 270.9 respectively) (P < 0.001). At 6 months, there was a significant linear decrease in P1NP (P = 0.036, η2 = 0.019) with increasing selenium supplementation but this effect was not apparent at 5 years. There was no significant effect of selenium supplementation on any other BTM.
Selenium supplementation reduced P1NP at 6 months but there were no significant effects on other BTM or after 5 years. Since P1NP is a marker of osteoblast function, the fall in PINP with increasing selenium supplementation suggests a reduction in new bone formation 5. The impact of this change in bone turnover on bone health remains to be determined.