Positive Health Online

Abstract

CHEONG and co-authors, Foods and Nutrition, Purdue University, 700 West State Street, West Lafayette, Indiana 47907-2059, USA, report that soya isoflavones do not prevent the loss of Calcium from bones in postmenopausal women.

Background

The aim of this 3-way crossover study was to identify the effective dose of soy protein isolate enriched with isoflavones for suppressing bone resorption in postmenopausal women using a novel, rapid assessment of antibone resorbing treatments.

Methodology

13 postmenopausal women were predosed with 41Ca iv. After a 200-day baseline period, subjects were given 43 g soy protein daily that contained 0, 97.5, or 135.5 mg total isoflavones in randomized order. The soy protein isolate powder was incorporated into baked products and beverages. Each 50-day intervention phase was preceded by a 50-day pre-treatment phase for comparison. Serum isoflavone levels and biochemical markers were measured at the end of each phase. 24-hour urine samples were collected approximately every 10 d during each phase for 41Ca/Ca analysis by accelerator mass spectrometry.

Results

Serum isoflavone levels reflected the amount of isoflavones consumed in a dose-dependent manner. None of the isoflavone levels had a significant effect on biochemical markers of bone turnover, urinary cross-linked N teleopeptides of type I collagen and serum osteocalcin, or bone turnover as assessed by urinary 41Ca/Ca ratios.

Conclusion

Soy protein with isoflavone doses of up to 135.5 mg daily did not suppress bone resorption in postmenopausal women.

References

Cheong JM et al. Soy isoflavones do not affect bone resorption in postmenopausal women: a dose-response study using a novel approach with 41Ca. Journal of Clinical Endocrinology & Metabolism 92 (2): 577-582, Feb 2007.