Author(s): KANEKO, T., YOSHIOKA, M., WAN, J., MAEDA, S., SHIMOJO, N., NAKATA, Y., KOSAKI, K., Institution: WASEDA UNIVERSITY, Country: JAPAN, Abstract-ID: 2209

INTRODUCTION:
Equol, a gut microbiota–derived metabolite of soy isoflavones, is associated with exercise-induced cardiovascular benefits; however, equol-producing ability varies substantially among individuals [1]. Dietary habits, including vegetarian diets and soy isoflavone intake, have been shown to influence equol-producing ability. Therefore, this study aimed to investigate whether replacing meat and fish with soy foods affects equol-producing ability.
METHODS:
This study was a secondary analysis of a published randomized controlled trial [2]. Sixteen overweight or obese Japanese adults, aged 52–72 years, were randomly assigned to a control group (n = 8) or a plant group (n = 8). All participants attended a weekly dietary weight-loss class for 12 weeks. Participants in the plant group were instructed to replace meat and fish with soy foods. Equol-producing status (producer or non-producer) was determined based on urinary equol levels (≥ 1.0 µmol/L) following a soy challenge. Group × time (pre- or post-intervention) interactions for body weight and plant protein intake were assessed using two-way repeated ANOVA. Interactions between group and equol-producing status for changes in urinary equol levels were assessed using two-way ANOVA.
RESULTS:
Body weight decreased over time in both groups (control: 73.3 to 66.9 kg; plant: 78.8 to 73.1 kg; P < 0.01), with no significant group or interaction effects (P for group = 0.15, P for interaction=0.48). Plant protein intake (% of energy) showed a significant group × time interaction (P = 0.02), increasing from 7.0% to 9.2% in the plant group compared with 7.3% to 7.7% in the control group. Before the intervention, 11 of 16 participants were equol non-producers (control: n = 6; plant: n = 5). After the intervention, only one non-producer in the control group became a producer. No changes in equol-producing status were observed among the non-producers in the plant group. Two-way ANOVA detected a significant main effect of equol-producing status on change in urinary equol levels (P = 0.01), without significant group or interaction effects (P for group = 0.13, P for interaction = 0.13). Among equol producers, changes in urinary equol levels tended to be greater in the plant group than in the control group (control: 21.9 ± 22.5 vs. plant: 82.0 ± 106.4 µmol/L; P = 0.08).
CONCLUSION:
Replacing meat and fish with soy foods did not alter equol-producing status. However, this dietary intervention may increase urinary equol levels among equol producers.

[1] Hayashi K et al. Equol-producing status affects exercise training-induced improvement in arterial compliance in postmenopausal women. J Appl Physiol (1985) 2021; 130: 827–835.
[2] Yoshioka M, Kaneko T, Wan J et al. Effects of replacing meat and fish with pulse intake on circulating fibroblast growth factor-23 levels during a 12-week dietary weight-loss intervention using the Four-Food-Group Point Method: a pilot randomized controlled study. Appl Physiol Nutr Metab 2025; 50: 1–15.