Another study, this one conducted at the University of Illinois and published in the Journal of Nutrition, provides more evidence that soy protein helps persons with diabetes prevent kidney disease and improve their cholesterol profile. This study, a seven month crossover trial, involved 14 men with type 2 diabetes and kidney disease. After the first month, during which baseline measurements were established for each man, they were divided into two groups, one of which received a daily serving of vanilla flavored protein powder made from soy protein while the other group was given protein powder containing casein (the primary protein in cow's milk). After eight weeks, the men were given no protein powder for four weeks and then switched over to the other protein powder for eight weeks. Serving size of both types of protein was 0.5g/kg/day.
While on the soy protein, the men's urinary albumin concentrations decreased by 9.5% but increased by 11.1% while on the casein diet. Higher amounts of albumin in the urine are a marker for deterioration in kidney function.
In addition, blood levels of beneficial HDL-cholesterol increased by 4.3% after the soy protein diet but tended to be lower after casein consumption.
Why were these beneficial effects seen with soy? The authors suggest that soy's isoflavones may be responsible for the improvement in cholesterol profile, while soy's higher levels of the amino acid arginine, a chemical precursor to a molecule called nitric oxide that dilates arteries, are responsible for improving blood flow in the kidney and thus kidney function.
Their conclusion: a simple dietary modification¡ªadding soy protein foods to the diet¡ªcould help persons with diabetes prevent kidney disease and improve their cholesterol profile.