Genistein, a plant-based antioxidant, helped control blood sugar, reduced risk for heart disease and increased bone mineral density (BMD) in postmenopausal women, in two new studies.
Researchers from the University of Messina, Italy, recruited 389 otherwise healthy postmenopausal women aged 47 to 67 with low BMD scores (between -1 and -2.5), a condition known as osteopenia. Scores below -2.5 indicate osteoporosis. The women ate a low-soy, low-fat diet for the first four weeks and then took a placebo or 54 mg of genistein per day for the next 24 months. All participants also took daily doses of calcium and vitamin D3.
At the beginning of the study and at 12 and 24 months, researchers measured blood fats, sugar, how well the cells used insulin to convert sugar into energy (insulin sensitivity), and risk factors for heart disease including signs of blood clotting, oxidation and inflammation. After 12 and 24 months, compared to placebo, the genistein group had significantly lower blood sugar levels and increased insulin sensitivity. After 24 months, compared to placebo, the genistein group had more normal clotting and less oxidation. Doctors noted that the genistein group had no change in blood fats. They concluded that genistein plus calcium and vitamin D3, along with a healthy diet, improved blood sugar control and reduced some risk factors for heart disease in postmenopausal women with osteopenia.
In the second study, using the same 389 women in the first study, researchers measured signs of bone forming and breaking down in the blood and urine, how well the pituitary gland regulated calcium, and the thickness of the uterine lining, a cancer-risk factor. At 24 months, the genistein group had increased BMD while the placebo group had lost BMD. Genistein produced no change in thickness of the uterine lining and, compared to placebo, the genistein group had fewer signs of bone breaking down and more signs of bone forming. Doctors noted that some participants reported gastrointestinal side effects and discontinued the study—19% in the genistein group, 8% for placebo—and concluded that genistein improved BMD in postmenopausal women with osteopenia. A 25g serving of soy protein contains about 25-75mg of a combination of isoflavones such as genistein, daidzein and glycitein.