Soy supplements may not improve blood glucose control in women with prediabetes (a condition in which blood glucose levels are elevated, but not high enough for a diagnosis of diabetes) or recently diagnosed with Type 2 diabetes, according to a recent study in the American Journal of Clinical Nutrition. Past research into soy’s effects on diabetes has yielded conflicting results.
Laboratory research has suggested that estrogen-like compounds in soy known as soy isoflavones might help to lower blood glucose levels. To test this theory, researchers at the Chinese University of Hong Kong recruited 180 postmenopausal women who either had prediabetes or had recently been diagnosed with Type 2 diabetes and had not yet begun treatment. The women were randomly assigned to one of three groups: one took a supplement containing milk protein, one a supplement containing milk protein and soy isoflavones, and the third a supplement containing soy protein and additional soy isoflavones each morning for six months. Aside from the addition of the supplement, the participants were instructed to maintain their usual diets.
At the end of the trial period, neither the soy protein with additional isoflavones nor the milk protein with isoflavones showed any clear benefit in controlling blood glucose or insulin levels. According to the researchers, the soy supplement had a “marginally favorable benefit” on the women’s blood glucose levels two hours after eating, but not enough to indicate that soy or isoflavone supplements are useful for lowering blood glucose in older women with prediabetes or Type 2 diabetes.
Nonetheless, the researchers note that this appears to be the first controlled clinical trial investigating the use of soy supplements in people with prediabetes and early Type 2 diabetes and suggest that “Additional studies that are based on longer trials using different soy and phytoestrogen regimens are warranted.”
To learn more, read the article “Soy supplements show no diabetes benefit in study” or see the study’s abstract in the American Journal of Clinical Nutrition.