Soy & Osteoporosis

Osteoporosis is a serious concern for women over age 40, due to the increased risk at the onset of menopause. Osteoporosis is a worldwide problem and the most prevalent metabolic bone disease in developed countries, including the United States.¹ Women are disproportionably affected by osteoporosis with fracture rates approximately twice as high as among men in developed countries.^2-4

There is considerable interest in the skeletal benefits of soy foods. In part, this is because Asian epidemiologic studies generally show that soy intake is positively associated with higher bone mineral density (BMD).⁵

Furthermore, in the only epidemiologic study to include fractures as an end point, relative risk was reduced by approximately one-third in Chinese women in the fifth quintile for soy protein consumption compared with those in the first quintile.⁶ During the four-and-a-half year follow-up period, nearly 1,800 fractures occurred among the 24,000 women enrolled in this study. Both the hormonal and non-hormonal properties of isoflavones may contribute to possible skeletal benefits of soy foods.⁷

At least 16 clinical trials have examined the effects of isoflavones – from either supplements or soy protein – on BMD in peri- or postmenopausal women.⁷ Overall, the clinical data are intriguing and suggest that isoflavones reduce bone loss, but the inconsistent results and relatively small size and short duration of most of the trials prevent definitive conclusions from being made.

Despite this, the data are sufficiently encouraging to recommend soy foods consumption for postmenopausal women who are concerned about bone health. Currently, the U.S. government is funding four large, long-term trials to examine the skeletal benefits of isoflavones for postmenopausal women. The results from these trials, which will be available within 2 to 3 years, will hopefully allow definitive conclusions to be drawn about the skeletal effects of soy foods.⁷

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References

1. Wasnich RD. Vertebral fracture epidemiology. Bone 1996;18 (3 suppl):179S-183S.
2. Chalmers J, Ho KC. Geographic variations in senile osteoporosis. The association with physical activity. J Bone Joint Surg [Br] 1970;52:667-675.
3. Xu L, Lu A, Zhao X, Chen X, Cummings SR. Very low rates of hip fracture in Beijing, People's Republic of China the Beijing Osteoporosis Project. Am J Epidemiol 1996;144:901-907.
4. Gupta A. Osteoporosis in India--the nutritional hypothesis. Natl Med J India 1996;9:268-274.
5. Messina M, Ho S, Alekel DL. Skeletal benefits of soy isoflavones: a review of the clinical trial and epidemiologic data. Curr Opin Clin Nutr Metab Care 2004;7:649-658.
6. Zhang X, Shu XO, Li H, Yang G, Li Q, Gao YT, Zheng W. Prospective cohort study of soy food consumption and risk of bone fracture among postmenopausal women. Arch Intern Med 2005;165:1890-1895.
7. Branca F. Dietary phyto-oestrogens and bone health. Proc Nutr Soc 2003;62:877-887.