Isolated soy protein added to the diets of 14 men, all military veterans under treatment for advanced stages of type 2 diabetes, significantly lowered unwanted proteins in their urine and slightly raised desired HDL cholesterol levels in their blood, researchers say.
The two improved areas are linked to kidney disease and coronary heart disease, respectively, in patients with type 2 diabetes. The Centers for Disease Control estimates that 18 million Americans have diabetes, with more than 90 percent being type 2 cases.
The study’s findings, published in the August issue of the Journal of Nutrition, surprisingly exceeded the expectations of participating scientists at the University of Illinois at Urbana-Champaign and suggest that more widespread testing is warranted.
“The number of type 2 diabetics is increasing to epidemic proportions, with the disease being found in younger and younger individuals everyday,” said Sandra R. Teixeira, who had pursued the research as the focus of her doctoral work at Illinois. “As a result, the rate also increases tremendously for diabetic complications, which include diabetic kidney disease and cardiovascular disease.”
The human findings confirmed those of a study published a year earlier using mice, said Teixeira, now a researcher focusing on type 2 diabetes for the Novartis Institutes for Biomedical Research in Cambridge, Mass.
“Our most remarkable result was that soy protein added to the diet, compared to animal source protein, in this case casein, resulted in a significant reduction in the amount of protein in the urine,” said John Erdman, a professor of nutrition in both the U. of I. College of Medicine and College of Agricultural, Consumer and Environmental Sciences. “Patients eating casein actually had an increase of urine protein levels.”
Participants of the study were men ranging in age from 53 to 73 who were recruited at the Veterans Affairs Illiana Health Care System (formerly known as the Danville Veterans Administration Medical Center) in Danville, Ill. Veterans diagnosed with diabetic nephropathy (kidney disease) took part in the study, but over the course of three seven-month study periods several had to be dropped because of changes in medications. Data from the remaining 14 men were used for statistical analysis.
The men consumed pre-measured amounts, based on each man’s weight, of either vanilla flavored isolated soy protein made from soybeans or casein, an animal-based protein. They were supposed to have substituted 50 percent of their daily protein intake with the pre-measured powders, but instead they consumed the powders as part of additional dishes or drinks in their diet.
“Our hypothesis was that we could slow down or maintain the same protein levels in the urine by introducing soy protein,” said Lea Ann Carson, a research dietitian in the department of food science and human nutrition at Illinois. “We actually had a reduction.”
Those consuming the soy protein had a 9.5 percent reduction in the excretion of urinary albumin, an undesired buildup of globular protein indicative of worsening kidney function. Participants eating casein had an 11.1 percent increase of urinary albumin. A common treatment for diabetic kidney disease has been a reduction in protein in the diet.
In Teixeira’s earlier study of type 2 diabetic mice, casein consumption had increased protein levels in the urine, while soy protein only prevented the levels from worsening.
Levels of HDL, often referred to as good cholesterol, were improved by 4.3 percent in the human study, but overall cholesterol ratios improved only slightly. HDL dropped just slightly in the men who consumed casein.