A study on soy supplements disappointed Chinese researchers considering blood sugar and insulin. The subjects were 180 postmenopausal women with pre-diabetes. The women took powdered supplements each morning for six months. One group got milk protein, while another got soy protein; the third group got both milk and soy in their powdered supplement. There was no clear difference among the groups with regard to blood sugar or insulin levels, and the investigators concluded that the evidence does not support the theory that soy can improve blood sugar control.
[American Journal of Clinical Nutrition, online March 24, 2010]