Supplements of calcium effectively increased the build up and bone mineral content in teenage girls, but the benefits are undone if the supplementation stops, suggests a new study.
An 18-month randomised trial found that a daily 792 mg calcium supplement boosted bone mineral content in girls, report the researchers in the American Journal of Clinical Nutrition. Moreover, the researchers from the University of Sheffield report that bone turnover also, measured using parathyroid hormone (PTH) levels, and markers of bone resorption (weakening of the bone) also decreased as a result of the intervention. "Calcium supplementation enhances bone mineral accrual in teenage girls, but the effect is short-lived," wrote lead author Helen Lambert. Osteoporosis is characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 75 million people suffer from osteoporosis in Europe, the USA and Japan.
Women are four times more likely to develop osteoporosis than men. Potential reduction of osteoporosis has traditionally been a two-pronged approach by either attempting to boost bone density in high-risk post-menopausal women by improved diet or supplements, or by maximising the build up of bone during the highly important pubescent years. About 35 per cent of a mature adult's peak bone mass is built-up during puberty. The Sheffield-based researched used fan-beam dual-energy X-ray absorptiometry, and four bone turnover markers to test the effects of calcium supplementation on bone health. They recruited 96 girls with a low habitual calcium intake (average intake of 636 mg per day) and an average age of 12, and assigned them to receive the daily calcium supplement or placebo (control).
At the end of 18 months, the bone mineral content (BMC) in the girls receiving the calcium supplements was greater at all skeletal sites except the hip. Moreover, bone mineral density (BMD) was significantly greater compared to the control group. The girls were then followed for another two years after the end of supplementation, and the researchers report that "gains in BMC and BMD and differences in bone resorption were no longer evident." Commenting on the mechanism, Lambert and co-workers proposed that the mineral most likely worked by suppressing bone turnover. These effects were then reversed once supplementation was discontinued. Calcium is reported to be the biggest seller in the US supplements industry. Annual sales were about $993m (€836m) in 2004, according to the Nutrition Business Journal.
Source: American Journal of Clinical Nutrition February 2008, Volume 87, Number 2, Pages 455-462 "Calcium supplementation and bone mineral accretion in adolescent girls: an 18-mo randomized controlled trial with 2-y follow-up"
Authors: H.L. Lambert, R. Eastell, K. Karnik, J.M. Russell, M.E. Barker