Health-Promoting Effects of a Dietary Fiber Concentrate from the Soybean Byproduct Okara in Rats

Okara (a byproduct of the soy milk industry) is rich in proteins (24.5−37.5 g/100 g of dry matter (dm)), lipids (9.3−22.3 g/100 g of dm), and dietary fiber (DF) (14.5−55.4 g/100 g of dm). It also contains isoflavones (0.14 g/100 g of dm). In the present study we fed female healthy Wistar rats either a standard rat diet or a supplemented 10% DF-rich okara (DFRO) diet for 4 weeks, and then we assessed several health parameters in the serum and the cecum compartments. In comparison to the control group, rats fed DFRO showed a significant decrease in weight gain (5.00 ± 1.22 g vs 2.00 ± 1.46 g, P < 0.03, during week 4) and in total cholesterol (65 ± 8 mg/dL vs 51 ± 5 mg/dL, P < 0.05) and a significantly increased antioxidant status (36.71 ± 15.31 μmol of Trolox equivalents (TEs)/g vs 69.75 ± 16.11 μmol of TEs/g, P < 0.0003) and butyrogenic effect (39.37%, P < 0.003) in the cecum. In addition, a significant enhancement in the apparent absorption (41.89 ± 1.64% vs 47.02 ± 2.51%, P < 0.004) and in the true retention (41.62 ± 1.60% vs 46.68 ± 2.55%, P < 0.005) of calcium was appreciated. In summary, these findings show for the first time that a concentrate DF from a soybean byproduct protects the gut environment in terms of antioxidant status and prebiotic effect. These results may highlight the development of an innovative soybean byproduct rich in DF which could be useful as a functional ingredient with health-promoting attributes.