T.O. Carpenter, M.C. DeLucia, J. Hongyuan Zhang, G. Bejnerowicz, L. Tartamella, J. Dziura, K. Falk Petersen, D. Befroy and D. Cohen "A Randomized Controlled Study of Effects of Dietary Magnesium Oxide Supplementation on Bone Mineral Content in Healthy Girls." The Journal of Clinical Endocrinology & Metabolism. Volume 91, Number 12, Pages 4866-4872.

1/30/2007 — Magnesium supplements during adolescence, a key time for bone formation, boosted bone health in 120 girls in the US — research that suggests the mineral could have long-term benefits.

There are two main approaches to prevent osteoporosis. First, optimise bone mass acquisition during adolescence, and secondly, minimise bone loss after menopause. About 35 per cent of a mature adult's peak bone mass is built-up during puberty.

Results of a prospective, placebo-controlled, randomized, one-year double-blind trial indicate that regular magnesium supplements during this important age could significantly improve bone mineral density, and could have benefits later in life concerning osteoporosis.

Osteoporosis is characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 10 million people suffer from osteoporosis in the US alone, while another 34m are believed to have low bone mass, which puts them at risk of developing the disease.

Women are four times more likely to develop osteoporosis than men.

“The role of magnesium as a determinant of bone mass has not been extensively explored… but no data from interventional studies in children and adolescents are available,” wrote lead author Thomas Carpenter from Yale University School of Medicine.

The researchers recruited 120 healthy Caucasian girls aged eight to 14 with daily magnesium intake less than 220 mg, and randomly assigned them to either a daily magnesium supplement (300 mg) or placebo for 12 months.

At the end of the study, Carpenter and his co-workers reported bone mineral content significantly increased in the hips of the girls in the magnesium supplement group, compared to placebo, while slight but non-significant increases were also observed in the lumbar spine bone mineral content.

“Compliance was excellent; 73% of capsules were ingested as inferred by pill counts,” said the researchers. No adverse effects due to the magnesium supplements were observed beside some mild diarrhoea in a small number of subjects, they added. Talking to Reuters Health, Carpenter said that such effects could be removed if the supplements were gradually phased in to the diet.

“Oral magnesium oxide capsules are safe and well tolerated,” wrote the researchers. “A positive effect of Mg supplementation on integrated hip BMC was evident in this small cohort.”

The study does have several limitations, most notably that the girls did not consume the recommended daily amount for girls in this age group (240 mg per day), raising questions as to whether the results can be generalized to the larger population.

Further research is necessary to investigate the role of magnesium supplements on bone health in other racial groups and magnesium replete subjects.

Dietary sources of magnesium include green, leafy vegetables, meats, starches, grains and nuts, and milk. Earlier dietary surveys show that a large portion of adults do not meet the RDA for magnesium (320 mg per day for women and 420 mg per day for men).