The effect of soy isoflavone on bone mineral density in postmenopausal Taiwanese women with bone loss: a 2-year randomized double-blind placebo-controlled study

Abstract

SummaryThe treatment of 300-mg/day isoflavones (aglycone equivalents) (172.5 mg genistein + 127.5 mg daidzein) for 2 years failed to prevent lumbar spine and total proximal femur bone mineral density (BMD) from declining as compared with the placebo group in a randomized, double-blind, two-arm designed study enrolling 431 postmenopausal women 45–65 years old.IntroductionThis study evaluated the effects of soy isoflavones on bone metabolism in postmenopausal women.MethodsFour hundred and thirty-one women, aged 45–65 years, orally consumed 300-mg/day isoflavones (aglycone equivalents) or a placebo for 2 years in a parallel group, randomized, double-blind, two-arm study. Each participant also ingested 600 mg of calcium and 125 IU of vitamin D3 per day. The BMD of the lumbar spine and total proximal femur were measured using dual-energy X-ray absorptiometry at baseline and every half-year thereafter. Serum bone-specific alkaline phosphatase, urinary N-telopeptide of type 1 collagen/creatinine, and other safety assessments were examined regularly.ResultsTwo hundred out of 217 subjects in the isoflavone group and 199 out of 214 cases in placebo group completed the treatment. Serum concentrations of isoflavone metabolites, genistein and daidzein, of the intervention group were remarkably elevated following intake of isoflavones (p < 0.001). However, differences in the mean percentage changes of BMD throughout the treatment period were not statistically significant (lumbar spine, p = 0.42; total femur, p = 0.39) between the isoflavone and placebo groups, according to the generalized estimating equation (GEE) method. A significant time trend of bone loss was observed at both sites as assessed by the GEE method following repeated measurement of BMD (p < 0.001). Differences in bone marker levels were not significant between the two treatment groups.ConclusionTreatment with 300-mg/day isoflavones (aglycone equivalents) failed to prevent a decline in BMD in the lumbar spine or total femur compared with the placebo group.

Soy Isoflavones and Osteoporotic Bone Loss: A Review with an Emphasis on Modulation of Bone Remodeling

“…46,74,75,77 Combined with the biphasic effect of SI, there might be no effect on preserving bone loss in long-term studies when the dose was too high (>200 mg/day). 78,79 According to Table 2, the practical SI dosage for a long-term study among western females might be around 80-120 mg/day.…”

“…Some studies showed significant prevention in bone loss (BMD/BMC) over the duration of the studies 35,46,47,[58][59][60][61][62][63][64][65][66][67][68] ; others did not prove to have significant effects. 18,[69][70][71][72][73][74][75][76][77][78][79] Bone remodeling is a slow process. It normally requires 6-18 months to reach a new equilibrium, and the time required to complete each cycle may be increased with age.…”

Soy Protein Isoflavones and Their Effect on Bone in Postmenopausal Women

“…In contrast, a meta-analysis by Taku et al [ 33 ] that included data on 1,240 menopausal women showed that a dose of 82 mg/day soy iso fl avones signi fi cantly increased spine BMD by 22.25 mg/cm [ 19,21,22 ] , all of which are essentially negative.…”

“…In another large 2-year double-blind placebo-controlled study of 431 Chinese postmenopausal women, aged 55-56 years, from Taiwan [ 22 ] , the highest dose yet evaluated of iso fl avones, 300 mg/ day containing 172.5 mg of genistein, was given in the form of three capsules, each with 50 mg taken two times a day; there was no signi fi cant effect on spine and hip BMD. In this study the baseline intake of iso fl avones was high (up to 53 mg/day) and the authors suggested that the high-baseline soy intake could mask the effects of iso fl avones on bone.…”

Does soy protein affect circulating levels of unbound IGF-1?

“…However, in the Asian studies, reduced risks were associated with extremely low soy protein intakes, which argue against an increase in IGF-1 contributing to the protection against fracture, and the association with soymilk intake was thought by the authors of this study to be due to the calcium it provided. Most interest in the skeletal benefits of soy is due to its high isoflavone content [69][70][71][72][73].…”