Soy protein consumption could help protect against bone loss in post menopausal women, suggests a new study that adds to previous findings linking soy to bone health in women.

Published in the December 2008 issue of Osteoporosis International, the study followed over 400 perimenopausal Chinese women for 30 months to investigate change in bone mineral density and its determinants.

The findings revealed that the fastest bone loss occurred in women undergoing menopause ¨C but that soy protein intake seemed to exert a positive effect on bone health, together with maintenance of body weight and physical fitness.

Soy and bone health

Limiting bone loss in post-menopausal women could ease the burden of osteoporosis, a disease that affects half of all women over the age of 50. According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is ?31.7 bn in Europe alone.

Previous studies have reported conflicting results concerning soy isoflavones (40 to 99 mg/d doses) and bone health for postmenopausal women. But a recent meta-analysis added to the debate by reporting that such doses of soy isoflavones (less than 90 mg/d) may improve bone density (Clinical Nutrition, doi:10.1016/j.clnu.2007.10.012).

Moreover, other studies from China have linked soy isoflavones to increases in bone mineral density (BMD), and a recent large study in the Archives of Internal Medicine (2005, Vol. 165, pp. 1890-1895) reported that high soy consumption was linked with a 48 per cent decrease in fractures for women who had been menopausal for less than 10 years.

New findings

The new study recruited 438 Hong Kong Chinese women, aged 45 to 55 through random telephone dialling and primary care clinic. Researchers took bone mass, body composition and lifestyle measurements at baseline and at 9-, 18- and 30-month follow-ups.

Menopausal status was classified as pre- or postmenopausal or transitional. Using multiple regression analyses derived from baseline and follow-up measurements, the researchers found that menopausal status was the strongest determinant of bone changes.

Premenopausal women had an annual bone loss of around 0.5 per cent. Women in the 'transitional' group had 2 to 2.5 per cent bone loss, and postmenopausal women recorded around 1.5 per cent loss.

"Multiple regression analyses, revealed that a positive regression slope of body weight was protective for follow-up bone loss at all sites. Number of pregnancy, soy protein intake and walking were protective for total body BMC. Higher baseline LM was also protective for neck of femur BMD," wrote the researchers.