Consuming diet rich in soy foods may help lower low-density lipoprotein cholesterol in individuals whose bodies are able to convert it to an estrogen-like compound called equol, study says

BETHESDA, Maryland , February 28, 2012 (press release) – Background: Recent analyses have challenged the effectiveness of soy foods as part of a cardiovascular risk reduction diet.

Objective: The objective of the study was to show whether equol status determines the effectiveness of soy foods to lower LDL cholesterol and to raise HDL cholesterol.

Design: Eighty-five hypercholesterolemic men and postmenopausal women (42 men, 43 women) participated in 1 of 3 studies that represented a range of soy interventions and that followed the same general protocol at a Canadian university hospital research center. Soy foods were provided for 1 mo at doses of 30–52 g/d for the 3 studies as follows: 1) soy foods with either high-normal (73 mg/d) or low (10 mg/d) isoflavones, 2) soy foods with or without a prebiotic to enhance colonic fermentation (10 g polyfructans/d), or 3) soy foods with a low-carbohydrate diet (26% carbohydrate). Studies 1 and 2 were randomized controlled crossover trials, and study 3 was a parallel study.

Results: The separation of the group into equol producers (n = 30) and nonproducers (n = 55) showed similar reductions from baseline in LDL cholesterol (−9.3 ± 2.5% and −11.1 ± 1.6%, respectively; P = 0.834), with preservation of HDL cholesterol and apolipoprotein A-I only in equol producers compared with reductions in nonproducers (HDL cholesterol: +0.9 ± 2.7% compared with −4.3 ± 1.1%, P = 0.006; apolipoprotein A-I: −1.0 ± 1.1% compared with −4.7 ± 1.0%; P = 0.011). The amount of urinary equol excreted did not relate to the changes in blood lipids.

Conclusions: Soy foods reduced serum LDL cholesterol equally in both equol producers and nonproducers. However, in equol producers, ∼35% of our study population, soy consumption had the added cardiovascular benefit of maintaining higher HDL-cholesterol concentrations than those seen in equol nonproducers. This trial was registered at clinicaltrials.gov as NCT00877825 (study 1), NCT00516594 (study 2), and NCT00256516 (study 3).

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