Eating a diet rich in both soy protein and isoflavones can protect menopausal women from bone weakening and osteoporosis, according to the results of a preliminary study presented at the Society for Endocrinology annual conference in Edinburgh.
Osteoporosis is a common condition where bones become brittle and fragile from tissue loss, causing 9 million fractures worldwide every year. In women, bone loss occurs most quickly in the years immediately after menopause because they produce less of the sex hormone estrogen, which protects against bone loss.
Soybean foods contain phytochemicals known as isoflavones that are similar in structure to estrogen and so could theoretically protect women against osteoporosis by mimicking the action of estrogen.
The fact that isoflavones act like a weak form of estrogen in the body concerns some women, particularly those at high risk for breast cancer. (It’s thought that estrogen can promote the growth of breast cancer cells.)
However, studies suggest that consuming soy reduces breast cancer risk in Asian populations. In western women, soy has not been shown to increase or decrease risk. (Western women may not consume enough soy isoflavones to lower breast cancer risk.) And studies have also linked a higher intake of soy foods such as tofu, soy beverages and soy flour with a lower risk of breast cancer recurrence.
In this study, researchers from the University of Hull gave two hundred women in early menopause a daily supplement containing soy protein with 66 milligrams of isoflavones or a supplement with soy protein alone for six months. The researchers investigated changes in the women's bone activity by measuring certain proteins (βCTX and P1NP) in their blood.
They found that the women on the soy diet with isoflavones had significantly lower levels of βCTX than the women on soy alone, suggesting that their rate of bone loss was slowing down and lowering their risk of developing osteoporosis. Women taking soy protein with isoflavones were also found to have decreased risk of cardiovascular disease than those taking soy alone.
Lead author of the study said: "We found that soy protein and isoflavones are a safe and effective option for improving bone health in women during early menopause. The actions of soy appear to mimic that of conventional osteoporosis drugs.”
A daily intake of 66 milligrams of isoflavones is equivalent to roughly one cup of firm tofu, two cups of soymilk or 2/3 cup of cooked soybeans.
Researchers next aim to investigate the long-term health consequences of using soy protein and isoflavones supplements, and whether it may also have benefits beyond bone health.
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