Effects of natural S-equol supplements on overweight or obesity and metabolic syndrome in the Japanese, based on sex and equol status

Objectives Epidemiologic studies indicate that soy intake has an important role in the prevention of age-related health problems. Daidzein, the principal isoflavone contained in soy, is converted to S-equol by the intestinal bacteria. Not all individuals, however, can produce S-equol, which is considered the most biologically active metabolite. We studied the effects of a natural S-equol supplement on metabolic parameters associated with overweight or obesity and metabolic syndrome. Methods The study was a randomized, double-blinded, placebo-controlled, crossover design with no washout period. All subjects were considered overweight or obese if they had a body mass index >= 25 kg/m2. Placebo or natural S-equol tablets containing 10 mg S-equol were orally ingested each day for 12 weeks. A total of 54 Japanese overweight or obese outpatients were enrolled. The equol phenotype was determined, and various metabolic parameters, including cardio-ankle vascular index (CAVI), were measured. Results Equol non-producers comprised 67.9% of the overweight or obese subjects. The ratio of equol non-producers in this overweight or obese subject group was higher than the previously reported ratio of equol non-producers (approximately 50%) in the general population. Compared with the placebo group, intervention with natural S-equol led to a significant decrease in HbA1c, serum low-density lipoprotein cholesterol (LDL-C) levels and CAVI score. Furthermore, the effect was more prominent in the subgroup of female equol non-producers. Conclusion The ratio of equol non-producers in overweight or obese populations might be higher than generally reported. Natural S-equol might have a role in glycaemic control and in the prevention of cardiovascular disease by its effects to lower LDL-C levels and CAVI scores in overweight or obese individuals.