Soya protein does not affect glycaemic control in adults with type 2 diabetes.

Evidence from observational, animal and human studies supports a role for soya protein and its isoflavones in the improvement of glycaemic control in type 2 diabetes. The objective of the present study was to determine the effect of isoflavone-rich soya protein on markers of glycaemic control in adults with type 2 diabetes. Using a randomised, crossover, double-blind, placebo-controlled design, adults with diet-controlled type 2 diabetes (n 29) consumed soya protein isolate (SPI) and milk protein isolate (MPI) for 57 d each separated by a 4-week washout. Blood was collected on days 1 and 57 of each treatment period for analysis of fasting HbA1C, and fasting and postprandial glucose, insulin and calculated indices of insulin sensitivity and resistance. Urine samples of 24 h were collected at the end of each treatment period for analysis of isoflavones. Urinary isoflavone excretion was significantly greater following consumption of SPI compared with MPI, and 20.7 % of the subjects (n 6) were classified as equol excretors. SPI consumption did not significantly affect fasting or postprandial glucose or insulin, fasting HbA1C, or indices of insulin sensitivity and resistance. These data do not support a role for soya protein in the improvement of glycaemic control in adults with diet-controlled type 2 diabetes and contribute to a limited literature of human studies on the effects of soya protein on the management of type 2 diabetes.

Soy protein reduces serum LDL cholesterol and the LDL cholesterol:HDL cholesterol and apolipoprotein B:apolipoprotein A-I ratios in adults with type 2 diabetes.

Type 2 diabetes is highly prevalent in North America and is associated with increased risk of cardiovascular disease (CVD). Evidence supports a role for soy protein in the reduction of serum lipids related to CVD risk; however, few studies have focused on adults with type 2 diabetes who are not on lipid-lowering medications and/or do not have diabetic complications. The purpose of this study was to determine the effect of soy protein isolate (SPI) consumption on serum lipids in adults with diet-controlled type 2 diabetes. Using a double-blind, randomized, crossover, placebo-controlled intervention study design, adults with diet-controlled type 2 diabetes (n = 29) consumed SPI (80 mg/d aglycone isoflavones) or milk protein isolate (MPI) for 57 d each separated by a 28-d washout period. Twenty-four-hour urine samples were collected on d 54-56 of each treatment for analysis of isoflavones and blood was collected on d 1 and 57 of each treatment and analyzed for serum lipids and apolipoproteins. SPI consumption increased urinary isoflavones compared with MPI. SPI consumption reduced serum LDL cholesterol (P = 0.04), LDL cholesterol:HDL cholesterol (P = 0.02), and apolipoprotein B:apolipoprotein A-I (P = 0.05) compared with MPI. SPI did not affect serum total cholesterol, HDL cholesterol, triacylglycerol, apolipoprotein B, or apolipoprotein A-I. These data demonstrate that consumption of soy protein can modulate some serum lipids in a direction beneficial for CVD risk in adults with type 2 diabetes.