Soy isoflavones attenuate bone loss in early postmenopausal Chinese women : A single-blind randomized, placebo-controlled trial..

Author: Ye YB, Tang XY, Verbruggen MA, Su YX.
Publication: Eur J Nutr. 2006 Jun 8.

About one third of menopausal women experience osteoporosis. The bone loss of menopausal women is caused by decreased estrogen levels. Hormone Replacement Therapy tries to restore he estrogen levels but has adverse effects, such as increased risk of endometrial cancer and breast cancer. Therefore, there is a need to develop alternative therapies to prevent bone loss without adverse effects. Epidemiological studies indicate that consumption of soy and soy isoflavones is associated with less bone loss. Animal studies have also illustrated the bone-sparing effect of soy isoflavones. In vitro studies indicate that soy protein with isoflavones or isoflavones extracts stimulate the growth of osteoblast (cells responsible for bone mass formation). Other studies about the effect of soy isoflavones on bone loss have not always give consistent results, probably because too low isoflavones levels have been used.

The aim of this study was to investigate the effect of isoflavones on bone loss in Chinese women. In total 90 early menopausal women, aged between 45 and 60 years, participated in this study. The women were divided in 3 groups:
  • placebo group: receiving no extra isoflavones
  • low-dose isoflavones group: receiving daily 84 mg isoflavones
  • high-dose isoflavones group: receiving daily 126 mg isoflavones.
For this study, a commercial isoflavones extract (Soylife Extra), made from soy germ, and provided by Acatris Holding BV was used. At the start of the study and after 6 months, different bone loss parameters were measured: bone mineral density of hip and spine, serum osteocalcin, bone-specific alkaline phosphatase, and urinary deoxypyridinoline.

The bone mass density of both the lumbar spine and femoral neck increased with supplementation of soy isoflavones. The higher dose (126 mg) of isoflavones was more affective than the lower dose (84 mg). The urinary deoxypyridinoline levels were significantly lower in the low-dose and high-dose groups. Deoxypyridinoline is a breakdown product of collagen and is a marker of bone turnover. There was no change observed in serum osteocalcin and bone-specific alkaline phosphatase. Soy isoflavones also reduced bone loss of the hip but the observed effect was not significant, probably because of the short period (6 months) of the test. Observational studies, which take into account the influence of diet over a longer period, showed that a daily intake of between 30 and 40 mg isoflavones resulted in a higher peak bone mass in young women and a better bone mass in Chinese women. During this study, the isoflavones at low and high levels were well tolerated. There were no reported adverse effects, except that some women reported thirst at the beginning of the test.

The study concluded that soy isoflavones attenuated bone loss of the spine and femoral neck in a dose-dependent manner. The reduced bone loss was possibly caused by the inhibition of bone resorption. Although this study involved an intervention of only 6 months, the authors recommend that more long-term studies needs to be conducted.Dietary isoflavones: biological effects and relevance to human health. J Nutr. 1999 Mar;129(3):758S-767S

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