Lee Swanson Research Update

Soy Supports Bone Health and Blood Sugar Metabolism

April 2008

Soy isoflavone supplements may lead to improvements in bone health and blood sugar metabolism in post-menopausal women, according to new research from Japan.

The results of the study, published in the journal Geriatrics & Gerontology International, supports the benefits of soy isoflavones in the aglycone form against osteoporosis and diabetes.

Earlier studies from China have linked soy isoflavones to increases in bone mineral density (BMD), while a recent large study in the Archives of Internal Medicine (165:1890-1895, 2005) reported that high soy consumption was linked with a 48% decrease in fractures for women who had been menopausal for less than 10 years.

"Our results suggest that four-week intake of fermented soybean soup containing 24 mg of isoflavone aglycone improves bone metabolism by inhibiting the excessive enhancement of bone resorption and promoting bone formation in post-menopausal women," wrote lead author Mari Mori from Mukogawa Women's University Institute for World Health Development.

The new randomized, test diet-placebo, independent parallel double-blind study involved 56 healthy post-menopausal women aged 47 to 70. The women were randomly assigned to receive an aglycone-rich fermented soybean soup, providing a daily isoflavone aglycone dose of 24 mg, or placebo soup for four weeks. The subjects did not eat any other soybean-based foods and isoflavones supplements for five weeks prior to the start and for the duration of the study.

Mori and co-workers report that isoflavone levels in the urine increased significantly after four weeks of supplementation, compared to placebo. These increases occurred in combination with an increase in the excretion of deoxypyridinoline, a marker for bone resorption (weakening). Moreover, levels of osteocalcin, a marker of bone formation (strengthening) were significantly increased after four weeks, they added.

"Those results indicated that four-week intake of fermented soybeans improves bone metabolism in post-menopausal women by attenuating the excessive enhancement of bone resorption as well as by promoting bone formation," the researchers wrote.

"In this study, we did not measure bone mineral density, as the ingestion period was relatively short. However, such a daily intake of fermented soybean, if continued, is expected to improve bone metabolism and to contribute to the primary prevention of osteoporosis," researchers added.

They also said that blood levels of insulin were significantly lower after four weeks of supplementation, compared to placebo, while blood sugar (glucose) levels were similar between the groups. "These results suggest that four-week intake of fermented soybeans improves insulin resistance in post-menopausal women whose isoflavone intake was restricted," they stated.

Geriatrics & Gerontology International 8(S1): S8-S15, 2007

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