12/8/2005 - Increasing magnesium intake could increase bone density in the elderly and reduce the risk of osteoporosis, suggests a large American study.

"Higher Mg intake through diet and supplements was positively associated with total-body [bone mineral density] BMD in older white men and women. For every 100 mg per day increase in Mg, there was an approximate 2 per cent increase in whole-body BMD," said Kathryn Ryder and colleagues.
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.

More than 2,000 volunteers aged 70 to 79 took part in the cross-sectional American study by completing a food-frequency questionnaire. All supplements and dietary intakes of magnesium were calculated from ingredients databases.

The authors did not identify the exact role of magnesium, but suggested it may be via calciotropic hormones, by acting as a buffer against acidic Western diets, or by substituting for calcium in the bones.

Magnesium intake was positively associated with BMD in white, but not black, men and women. These observations could be due to racial difference in calcium regulation or nutrient responses.

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).

Responding to this study, a spokesperson for the UK-based charity, the National Osteoporosis Society, said: "Although there have been previous studies into the effect of magnesium on bone density, it is always encouraging to learn of studies which help build upon our knowledge of bone health."

"Some research has suggested that a low magnesium level may be a risk factor for osteoporosis although magnesium deficiency is, in fact, very rare in humans. As yet there is no evidence that magnesium supplementation reduces fracture risk," she said.

For healthy bones the Society recommends a mixed, well-balanced calcium-rich diet and regular weight-bearing exercise.

The study was published in the Journal of the American Geriatric Society (November, Vol 53, No 11, pp 1875-1880).