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Effects of Different Milks on Plasma Lipids logo

Effects of Two Types of Soy Milk and Dairy Milk On Plasma Lipids in Hypercholesterolemic Adults

Preliminary studies investigating the cholesterol-lowering potential of soy protein concluded that soy protein is an effective strategy to lower cholesterol, leading the FDA’s approval of a health claim for soy protein at a dose of 25 grams/day. However, subsequent trials found the cholesterol-lowering power of soy protein to be less pronounced and not clinically significant. One reason for the inconsistent findings could be the different types of soy products used in the studies, mostly soy protein isolate, and very few less processed soy products. The aim of this study was to compare the effect of two types of soy milk – one made from whole soy beans and one from soy protein isolate – on plasma lipids, insulin, and blood sugar.

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Eligible Participants

  • Generally healthy adults, 30-65 years of age
  • Having moderately elevated LDL-cholesterol but not taking lipid-lowering medications
  • Having a Framingham risk score of ≤10% based on gender, age, LDL-cholesterol, HDL-cholesterol, blood pressure and diabetes

Study Design

Twenty-eight participants were randomly assigned to drink one of 3 types of milk for 4 weeks, in a cross-over design: a whole soy bean (WB) beverage, a soy protein isolate (SPI) beverage, or a dairy milk (DM) as control. All participants drank all 3 types of milk. Each type of milk provided 25 grams of protein, consistent with the FDA health claim. Fasting blood samples were collected at the beginning, in the middle (at 15 days), and at the end of each 4-week milk phase to measure blood lipids, insulin, and blood sugar.

Conclusions

The results of this study show that a 25-gram dose of daily soy protein from soy milk led to a modest 5% lowering of LDL-cholesterol compared to dairy milk in adults with moderately elevated concentrations. The effect was virtually identical for the two distinct types of soy milks - one made from whole soy beans and one from soy protein isolate. Neither soy milk significantly affected other lipid variables, insulin or glucose.

Research