Alcohol-Extracted, but Not Intact, Dietary Soy Protein Lowers Lipoprotein(a) Markedly

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Abstract
We previously found that dietary soy protein produces higher lipoprotein(a) [Lp(a)] plasma concentrations than does casein. This study tested the hypothesis that soy protein contains Lp(a)-raising alcohol-removable components. Twelve normolipidemic women and men consumed, in a crossover design, liquid-formula diets containing casein, soy protein, or alcohol-extracted soy protein. Dietary periods of 32 days were separated by washout periods on self-selected diets. Fasting lipid and Lp(a) levels were measured throughout. Median Lp(a) concentration was >2-fold greater after 28 to 32 days on a soy protein diet than after an extracted soy protein diet ( P P 60% below baseline ( P P <0.01, respectively). Low density lipoprotein cholesterol concentrations were not different after the 3 experimental diets. The data indicate that (1) dietary soy protein can increase Lp(a) concentrations, (2) this effect is eliminated after alcohol extraction, and (3) high Lp(a) concentrations may be markedly reduced by diet.