Effects of Soy on Blood Sugar Levels

Studies have shown that soybean consumption affects blood sugar and its regulation. The present study analyzed previous studies to come to a more concrete conclusion. The results showed that the consumption of soy did not affect blood sugar and its control. However, some studies revealed that whole soy foods or a soy-rich diet could affect the blood sugar favorably.

Diabetes is a rising public health issue across the world. Diet control and modifications are important measures to keep rising blood sugar under control in diabetics and those susceptible to the disease. Soybean and its derivatives form an important part of the Asian diet. These are a good source of complex carbohydrates, vegetable protein, soluble fibers, polyunsaturated fat and phytoestrogens (isoflavones). These agents present in soy may help in blood sugar control as seen in several animal studies. Animal studies have also shown that these agents reduce the need for insulin therapy. Insulin is a blood sugar reducing hormone that is deficient in diabetics. This needs to be given as injections to bring down blood sugar levels. However, no clear results have been obtained from human studies. Some studies show benefits while others fail to do so. This study was undertaken to understand better the benefits of soy on blood sugar control.

The analysis involved 24 human studies with 1,518 participants. The authors searched various medical journal databases to gather these studies, and those up to March 2010 were included in this analysis. Each of the studies tested in detail the type of soy used, patient characteristics, outcome and relative effect of soy on blood sugar. Apart from fasting blood sugar (blood sugar after an overnight fast of six to eight hours), insulin hormone levels were also assessed.

* The results revealed that soy intake was not linked to better blood sugar control.
* The figures showed that the average difference in fasting blood sugar on soy intake was –0.69 mg/dl and average difference in fasting level of blood insulin was –0.18 mg/dl. Both results did not differ significantly enough from non-soy consumption groups to deem soy effective.
* However, a favorable change in the fasting blood sugar and insulin levels was noted when whole soy foods and soy diets were used. This whole soy diet is opposed to purified forms of soy where the protein or other beneficial chemicals like isoflavones have been extracted.

The authors state that only fasting blood sugar and insulin were measured in many of the studies. More detailed analyses of soy’s effects on other parameters of diabetes like glycated hemoglobin (HbA1C, which denotes long-term blood sugar control) and sensitivity to insulin are necessary in the future to understand the link better, state the researchers.

Soy intake has been shown to be beneficial in blood sugar control in animal diabetics. However, this is not proved concretely in human studies. This study is a collation of previous human trials and it shows that consumption of soy does not demonstrate a “notably favorable effect on the reduction of fasting glucose and insulin concentrations, although subgroup analyses showed a favorable change in fasting glucose concentrations in trials that used whole soy foods or a soy diet.” This study also shows that there is a wide variation in insulin levels of the participants. The authors suggest further larger and longer term studies to see if soy based foods and diets could be used in management of diabetes and related dietary modifications.

For More Information:
Effects of Soy Intake on Glycemic Control: A Meta-Analysis of Randomized Controlled Trials
American Journal of Clinical Nutrition, March 2011
By Zhao-min Liu; Yu-ming Chen; Chinese University of Hong Kong, Shatin, New Territories, Hong Kong and Sun Yat-sen University, Guangzhou, China

*FYI Living Lab Reports Are Summaries of the Original Research.

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