Biotransformation of soy isoflavones and enhanced cholesterol lowering effect with an oligofructose‐enriched inulin in equol producers

Objective: To assess whether the hypocholesterolemic effect of soy can be enhanced with an oligofructose‐enriched inulin (OF‐IN) by promoting the biotransformation of colonic soy isoflavones (i.e. equol production). Method: 23 hyperlipidemic adults (11M, 12F; 58±7y; LDL‐C, 4. 1±0.7mmol/L) completed three 4‐week phases: OF‐IN (10 g/d) and low‐fat dairy (control), and soy foods (isoflavones, 61 mg/d) with or without OF‐IN (10 g/d). Fasting blood lipids and anthropometrics were measured biweekly. Urine (24h) was collected at baseline and at the end of each phase. Results: A stepwise reduction in TChol:HDL‐C was observed for OF‐IN (0.25±0.13, P=0.08), soy (–0.07±0.08, P=0.41) and soy plus OF‐IN (–0.36±0.14, P=0.02), compared to baseline. Preliminary analysis suggested that this effect was seen most clearly in equol producers (n=7). TChol:HDL‐C for equol producers was 0.09±0.16 on OF‐IN, –0.23±0.14 on soy, and –0.72±0.42 on soy plus OF‐IN, compared to baseline. For non‐equol producers, TChol:HDL‐C was 0.41±0.17, 0.04±0.09, and –0.17±0.08, respectively. Conclusion: Intake of soy in conjunction with OF‐IN resulted in greater improvements in the lipid profile than their intake alone, suggesting a synergistic effect. This association was more prominent in equol producers possibly related to increased biotransformation of soy isoflavones. Funding: Heart and Stroke Foundation of Ontario, ORAFTI Group