How soy protects against diabetes complications

People with type 2 diabetes have a four to sixfold greater risk of death from heart disease and stroke ⁷ . Including heart-protective lifestyle strategies is therefore especially important. Men with type 2 diabetes given a soy beverage (containing soy protein, isoflavones and soy dietary fibre) twice daily for six weeks reduced their LDL ('bad') cholesterol by 10 per cent, triglycerides by 22 per cent, homocysteine by 14 per cent and ApoB100 by 30 per cent ⁸ . The significant improvement in these cardiovascular risk markers was seen even in people with near-normal blood fat values.

Another study of men with type 2 diabetes ⁹ , similarly found that soy protein added to the diet lowers LDL cholesterol and triglycerides (another fatty substance in the blood linked with heart disease). The soy protein containing diet also reduced the loss of 'albumin' (a protein) in urine by 9.5 per cent, indicating that soy is beneficial in slowing the progress of kidney disease.

In diabetic people who already have kidney disease, replacing some animal protein in the diet with soy protein, may improve kidney function even more than by restricting the amount of total protein consumed. A small study of patients from Tehran found that there was a significant reduction in protein loss in the urine and an improvement in kidney function ¹⁰ when their already moderately protein restricted diets (providing 0.8 grams of protein per kilogram of body weight) were further modified to ensure that 35 per cent of protein came from soy.

Studies in animals also support the view that soy protein may offer advantages over animal proteins for managing diabetes and its complications.

A study with diabetic mice showed that even at high levels of protein intake (24 % of calories - a level typically consumed by people who follow high protein diets) soy protein does not increase the loss of albumin in the urine, thereby reducing the strain on the kidneys in a similar way to how a low protein diet (regardless of the source of protein) protects the kidneys ¹¹ . These findings are encouraging since low protein diets have been commonly recommended to people with kidney disease to slow down the decline of kidney function but these diets have had poor acceptance and compliance. Substituting soy protein for some animal protein in the diet may be one way to preserve the kidneys without having to reduce the total quantity of protein consumed, thereby improving compliance with the diet.

Another study in rats suggests that soy protein, as compared to animal protein, may increase the production of adiponectin from fat tissue. In recent years it has been shown that fat tissue in the body makes many types of proteins, which are released into the blood stream and provide various and vast reaching effects in the body. Adiponectin is one important protein since low levels in the body have been linked with insulin resistance and diabetes. It has been suggested that soy protein may be one way to increase adiponectin, which has anti-diabetic properties ¹² .

While further research is still needed to determine the exact role of soy protein in preventing diabetes and reducing complications in people with this condition, the nutritional profile of soy beans and soy foods reveals that they are beneficial for the whole family to enjoy. Soy foods and beverages are generally low in fat, particularly saturated fat, and are naturally cholesterol free. The protein in soy beans has been extensively studied and shown to reduce blood cholesterol levels - even in people without diabetes. Soy foods are rich in isoflavones, which act as antioxidants in the body. In common with other legumes, soy foods have a low Glycaemic Index (GI), important in controlling blood sugar levels, and soy beans are rich in dietary fibre.