Plasma cholesterol-lowering effects of soymilk and okara treated by lactic acid fermentation in rats

We investigated the effect of lactic acid-fermented soymilk, in which a portion of soymilk was replaced with okara, on plasma and liver lipid concentrations in rats. Male Sprague-Dawley rats were fed a high-cholesterol diet (control diet) or test diet in which 20% of the diets were replaced by soymilk, fermented soymilk or a fermented soymilk/okara mixture. Fermented soymilk/okara was expected to be smoother in taste because finely powdered okara was used, instead of intact soybeans. Only rats fed a fermented soymilk/okara diet showed a significantly and continuously lower level of plasma total cholesterol. The hepatic triglyceride concentration in the rats fed the soymilk and fermented soymilk/okara diets showed significantly lower levels than rats fed the control diet. These results suggest that a mixture of fermented soymilk and okara has a significant advantage of the beneficial effects of okara, and shows greater plasma cholesterol-lowering and hepatic lipid-lowering effects than fermented soymilk alone. Therefore, fermented soymilk/okara is available as a functional food for prevention of hyperlipidemia. In addition, okara, which has been discarded as industrial waste, could be efficiently used as fermented soy food.