The Human Evidence on S-Equol: What the Published Trials Actually Say

Part 2 of the Dr. Morgan S-Equol Science Series. Read Part 1: What Is S-Equol? first. This article summarizes published human research cited in the Dr. Morgan S-EQUOL PLUS Physician Professional Guide v4. It is for education only and is not medical advice.

The short version

There are only a handful of published human trials on S-equol and menopausal hot flashes. This article lays out each one — who ran it, how many people, how long, what it found, and where it falls short. We present the unsupportive evidence alongside the supportive — the boundaries of the evidence matter as much as the evidence itself.

1. Aso 2012: positive on hot-flash frequency at 10 mg/day

The most-cited trial: 160 equol-nonproducing Japanese postmenopausal women, randomized, double-blind, placebo-controlled, 12 weeks. Hot-flash frequency fell 58.7% from baseline in the S-equol 10 mg/day group versus 34.5% with placebo — a between-group difference of p = .009.

Three qualifications must travel with that result:

1. It was an ingredient trial, not a trial of the finished Morgan formulation (S-equol 10 mg + genistein 16.7 mg AIE).
2. Participants were a selected population (nonproducing Japanese postmenopausal women) — the result cannot be generalized to everyone.
3. The placebo group itself improved by 34.5% — placebo responses in hot-flash trials are inherently strong.

2. Jenks 2012: no placebo group limits the conclusion

102 participants, 8 weeks, randomized and double-blind, comparing S-equol at 10, 20, or 40 mg/day against soy isoflavones. Hot-flash reductions at week 8 were similar across groups. The key problem: there was no placebo group, so the trial cannot answer the most basic question — whether S-equol beats placebo.

For completeness, its secondary analyses: in a cumulative 8-week analysis, the 40 mg/day group reduced hot flashes more than the soy-isoflavone group (p = .021), and the 10 and 20 mg/day groups scored better on muscle and joint pain. These were secondary analyses against soy isoflavones — not placebo — and should be interpreted with discount.

3. Ishiwata 2009: significance centred on 30 mg — and on mood outcomes

134 participants, 12 weeks, randomized, double-blind, placebo-controlled, in three arms: placebo, 10 mg/day, and 10 mg three times daily (i.e., 30 mg/day). Per the published abstract, statistically significant findings centred on the 30 mg/day group: versus placebo, depression scores fell significantly (P < .05), tension–anxiety and depression–dejection on the mood scale improved significantly (P < .05), fatigue improved significantly (P < .01), and vigor increased significantly (P < .05). The authors concluded S-equol improved mood-related symptoms in peri- and postmenopausal non-producers.

Two things must be stated plainly: first, the positive outcomes were mood-related, not hot-flash frequency; second, results at the higher 30 mg/day dose cannot be transferred directly to a 10 mg product.

4. Daily 2019: a systematic review of 6 studies, 779 participants

Pooling 6 studies (779 participants total), with 5 studies (728 participants) entering the meta-analysis. The pooled result favoured equol for hot-flash outcomes — but individual study findings were not uniform (of the 5 in the meta-analysis, 2 showed no significant benefit and 3 reported significant benefit), and results need to be read in the context of heterogeneity and sensitivity analyses.

Again the scope note: this is an ingredient-level literature review, not a meta-analysis of the Morgan formulation.

5. NAMS 2023: the guideline says “not recommended”

The 2023 North American Menopause Society position statement on non-hormonal therapies did not recommend soy foods, soy extracts, or the soy metabolite equol for vasomotor symptoms (hot flashes/night sweats), because the evidence was limited or inconsistent. It also states clearly: hormone therapy remains the most effective treatment for vasomotor symptoms.

6. The evidence boundary table: what is and is not supported

The guide also states explicitly: cognition, dementia prevention, prostate outcomes, bone outcomes, and cardiovascular outcomes are not presented as benefits of this product.

The one-line summary

The full picture: one placebo-controlled trial positive on hot-flash frequency at 10 mg/day (Aso 2012 — selected population, ingredient level), one placebo-controlled trial positive on mood outcomes at 30 mg/day (Ishiwata 2009), one systematic review favouring equol overall (but with inconsistent individual studies), one trial limited by the absence of a placebo group (Jenks 2012), and one guideline “not recommended” (NAMS 2023). That is all of it — no more, no less. In Part 3: licence and safety — what NPN 80143622 authorizes, and what to check before use.

Coming next — Part 3: Licence and safety: what NPN 80143622 covers, who should ask a professional first, and when to stop use.

References cited in this article

1. Aso T et al. J Womens Health. 2012;21:92-100. PubMed 21992596
2. Jenks BH et al. J Womens Health. 2012;21:674-682. PubMed 22409590
3. Ishiwata N et al. Menopause. 2009. PubMed 19131846
4. Daily JW et al. J Med Food. 2019;22:127-139. PubMed 30592686
5. The North American Menopause Society. Menopause. 2023;30:573-590. PubMed 37252752

The complete reference list for this series appears in Part 4.

Ingredient-science content for education only; not medical advice. S-EQUOL PLUS (NPN 80143622) is a licensed natural health product in Canada; its authorized use is “May reduce severe and frequent menopausal symptoms (such as hot flashes and/or night sweats).” Always read and follow the product label. Licence status can be verified by NPN in Health Canada’s Licensed Natural Health Products Database.