Lee Swanson Research Update

Soy Protein Appears to Reduce Cholesterol Levels for Diabetics

September 2009

Increased intakes of soy protein may reduce cholesterol levels in people with type 2 diabetes, says a new study that expands on the heart-healthy potential of soy.

Consumption of 40 grams of soy protein isolates (SPI) per day for 57 days resulted in significant reductions in both LDL cholesterol and the ratio of LDL to HDL cholesterol, compared to consumption of the same dose of milk protein, according to results published in the Journal of Nutrition.

"This study provides evidence for soy as a dietary preventive strategy for adults with type 2 diabetes to reduce their cardiovascular disease risk and, in so doing, improve their quality, and possibly length, of life," wrote the researchers, led by Alison Duncan from the University of Guelph, Guelph, ON, Canada.

The association between soy protein and blood lipid levels led the Food and Drug Administration (FDA) to approve a cardiovascular disease (CVD) reduction claim for soybean protein in 1999.

"This study therefore adds to the literature through its particular emphasis on prevention by studying adults with type 2 diabetes who are free of diabetic complications and not taking glycemic or lipid-lowering medications," wrote Duncan and her co-workers.

The researchers recruited 29 type 2 diabetics for their double-blind, randomized, crossover, placebo-controlled intervention study. The participants were assigned to consume a daily dose of soy protein isolate, which also contains 80 mg of aglycone isoflavones, or milk protein isolate for 57 days. At the end of the intervention they underwent a 28-day washout period prior to being crossed over to the other intervention.

According to their findings, the soy protein intervention was associated with a significant reduction in LDL cholesterol levels of a 0.17 mmol/l, a reduction in the ratio of LDL to HDL cholesterol of 0.03 points and drops in the ratio of apolipoprotein B:apolipoprotein A-I, compared to the milk protein intervention.

Apolipoprotein B is the main apolipoprotein of LDL cholesterol and is responsible for the transport of cholesterol to tissues. In high concentrations it has been linked to plaque formation in the blood vessels, although the mechanism behind this is not clear.

"The inclusion of apolipoproteins in future soy intervention studies is highly warranted; their relevance to CVD risk is well established and there is a particular emphasis on the apolipoprotein B:apolipoprotein A-I ratio as highly predictive in the evaluation of cardiac risk," wrote the researchers.

The ratio of total cholesterol to HDL cholesterol, reported to be the most specific lipid risk factor for CVD, was not affected by the intervention, they added. No changes in HDL cholesterol were noted.

"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," wrote the researchers.

Journal of Nutrition 139(9):1700-1706, 2009

New to Natural Health?
Tools
Customer Service