Soya and Bone Health

D. Lee Alekel, PhD, RD
Professor-In-Charge, Human Metabolic Unit
Iowa State University Ames,IA  50011  USA
Email:  alekel@iastate.edu
Homepage:  http://www.fcs.iastate.edu/fshn/faculty/alekel.htm

          Soya contains a myriad of substances purported to have health benefits, one of which is on the skeleton. This review focuses on isoflavones (estrogen-like compounds) because most published studies have been conducted on the naturally occurring isoflavones from soya foods.
           Observations suggest that soyabeans contribute to bone health, as indicated by the low rate of hip fracture in Asians originating from the Pacific Rim, the lower urinary calcium losses with soya versus animal protein diets, the effectiveness of the synthetic ipriflavone to prevent and treat postmenopausal osteoporosis, and the in vitro and in vivo estrogenic activity of soya isoflavones.
            The end-points that have been used to assess bone changes include bone mineral density (BMD) measurements using dual-energy X-ray absorptiometry (DXA) and circulating or urinary biochemical bone markers.  This summary of peer-reviewed papers concentrates on prospective human studies examining the effect of isoflavone-rich soya protein on BMD.
            Four prospective studies have been published thus far measuring bone mass as an outcome in response to soya isoflavone intake. Two of these studies were designed specifically to examine bone as the primary outcome. Two studies used soya protein isolate, one used soya foods, and one examined usual soya food intake among Asians as the source of isoflavones.
           Evidence of a bone-protective effect of isoflavone-containing soya is both intriguing and encouraging, but nevertheless speculative at this time. Still, these human studies suggest that isoflavones may attenuate lumbar spine bone loss in women. If continued throughout menopause, this attenuation of loss might decrease lifetime osteoporotic risk. Since a bone-remodeling cycle ranges from 30-80 weeks, these short-term preliminary studies cannot address whether such bone-sparing effects would be sustained long-term. We cannot determine whether the reported bone-sparing effect is due to treatment or is an artifact of the bone-remodeling transient, but a longer-term study in Asian women suggests true bone sparing. A study of longer duration is needed to resolve whether soya isoflavones will affect the remodeling balance in favor of bone formation. 

Read more about Effects of Soya on Bone Health in Post Menopausal Hormone Replacement Therapy.... Click Here

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