Mechanism Explained · Women’s Midlife
Why Soy Doesn't Seem to Work for Some People: Equol Producers and Non-Producers
Direct answer
People can metabolize the same soy isoflavone differently. Certain gut bacteria convert daidzein into S-equol. After a standardized soy challenge, researchers may classify participants as equol producers or non-producers based on the equol they measure in urine.
That classification helps explain why a soy challenge can lead to different equol measurements. It cannot tell you why an individual did or did not notice a benefit from soy or predict how they will respond to a supplement.
Key points
- Producer status describes a measured conversion under a specific test protocol.
- A soy challenge gives the body a precursor. Taking already-formed S-equol bypasses the initial conversion from that precursor.
- A clinical trial that enrolled only non-producers cannot compare their responses with those of producers.
Scientific background
Daidzein is one of several isoflavones found in soy. Some gut bacteria can convert it into S-equol. In a soy challenge, investigators standardize the intake and sample timing and apply a rule for classifying the result. A person whose result falls below the study’s cutoff may be classified as a non-producer for that protocol.
What the research examined
Atkinson and colleagues incubated stool samples from seven equol producers and six non-producers with daidzein for five days. This laboratory experiment tested bacterial conversion outside the body.
Aso and colleagues used a standardized soy challenge and urine measurements to screen postmenopausal Japanese women. In a separate randomized, double-blind trial, they assigned 160 screened non-producers to a natural S-equol preparation, SE5-OH, or placebo for 12 weeks. The study preparation provided 10 mg of S-equol per day.
What the studies found
In the Atkinson experiment, samples from the producer group generally converted daidzein into equol under oxygen-free conditions. The non-producer samples did not form equol under the conditions tested. In the Aso study, urine testing determined who qualified for the trial. A second screening measurement excluded some candidates who had qualified on the first test.
What the studies do not establish
The laboratory experiment did not measure symptoms after soy intake. The Aso trial enrolled non-producers and did not randomize participants to soy. Neither study establishes that producer status predicts a clinical response to soy or that producers and non-producers respond differently to an S-equol supplement.
Limitations
The laboratory study used a small, selected sample. The classification depends on the challenge, sample timing and cutoff. The clinical trial enrolled a selected population and tested one preparation, so its findings cannot establish effects in other populations or formulations.
Evidence context
Ingredient Evidence — Atkinson et al. studied bacterial conversion of daidzein in a laboratory model. Aso et al. studied an external S-equol preparation in a selected population. Finished-product Evidence — Neither study was conducted on the finished DR.MORGAN product.
Relationship to DR.MORGAN
S-EQUOL PLUS contains already-formed S-equol. For this product’s authorized use and directions, consult the Canadian product licence for NPN 80143622.
References
- Atkinson C, Berman S, Humbert O, Lampe JW. In vitro incubation of human feces with daidzein and antibiotics suggests interindividual differences in the bacteria responsible for equol production. Journal of Nutrition. 2004;134(3):596–599. DOI and original paper · PubMed 14988453.
- Aso T, Uchiyama S, Matsumura Y, et al. A natural S-equol supplement alleviates hot flushes and other menopausal symptoms in equol nonproducing postmenopausal Japanese women. Journal of Women’s Health. 2012;21(1):92–100. DOI 10.1089/jwh.2011.2753 · PubMed 21992596 · Original full text.
- Setchell KDR, Clerici C. Equol: History, chemistry, and formation. Journal of Nutrition. 2010;140(7):1355S–1362S. DOI · PubMed 20519412 · Full text.
- Health Canada. Licensed Natural Health Products Database. S-EQUOL PLUS / EquoPro, NPN 80143622.