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

Clin Endocrinol (Oxf). 2013 Mar;78(3):365-72. doi: 10.1111/j.1365-2265.2012.04400.x.


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/m(2) . 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Asian Continental Ancestry Group
  • Cholesterol, LDL / blood
  • Dietary Supplements
  • Equol / therapeutic use*
  • Female
  • Glycated Hemoglobin A / metabolism
  • Humans
  • Male
  • Metabolic Syndrome / blood
  • Metabolic Syndrome / prevention & control*
  • Obesity / blood
  • Obesity / prevention & control*
  • Overweight / blood
  • Overweight / prevention & control*
  • Phytoestrogens / therapeutic use*


  • Cholesterol, LDL
  • Glycated Hemoglobin A
  • Phytoestrogens
  • Equol