Aside from all the points you make, this was a 12 week study which immediately disqualifies it. The placebo affect in VMS studies is significant and therefore requires a longer trial. Every study that shows black cohosh works is less
than 4 months. 52 week trial- no better than placebo. I honestly don’t know how this one made it through the review board.
I have changed so many things about my lifestyle. I’ve incorporated more plant-base meals, started running again (I was doing mostly strength before), started seeing a therapist and meditate and journal every day…. And all that did make me feel better. But what tipped the scale for me was cutting out alcohol completely. I haven’t had a hot flash since (im 49 and was a mostly 1-4 drinks on weekend or holiday nights drinker). I had night sweats every time the darned stuff touched my lips, regardless of amount. But I’m still doing all the other things too. Maybe it was a cumulative thing. 🤣
I'll addressing that in a follow up post, but there is no data that shows that a moderate amount of soy is harmful for women who have had breast cancer.
A few more: do phytoestrogen molecules break down in digestion? How easily are they absorbed by the digestive system? Does cooking affect amounts in food (is raw tofu in a smoothie providing more than cooked in a stir fry?)
1. Yes, soy works via estrogen receptors but much more weakly than estrogen itself. Isoflavones (the phytoestrogens in soy) preferentially bind to ER-beta, which is considered more protective, unlike ER-alpha, which is more active in breast and uterine tissue. So the action is estrogen-like, but more selective and weaker.
2. Because of this, soy doesn’t carry the same risks as hormone therapy. In fact, it can block stronger estrogens in some tissues.
3. For women with ER+ breast cancer, most studies show that soy foods are safe and may even lower recurrence risk.
As always, it’s best to talk to your doctor, but the science around soy is more reassuring than many realize.
Breast oncologists used to prohibit soy products, but it seems that phytoestrogens work more like a SERM than actual estrogens. So, thr no soy thing is no longer true for women with breast cancer.
I think the whole a dding soy to diet came about because japanese and chinese women who follow a traditional diet are reported to have less hit flashes and a lower incidence of breast cancer. However, these women grow up eating soyfoods and don’t them as an adult. There may be an entirely different mechanism at work.
Thank you for taking the time to dissect the evidence. One thing I’d add, especially when it comes to soy and vasomotor symptoms, is that the individual ability to metabolize soy isoflavones into equol may explain a lot of the conflicting results across studies.
Soy contains isoflavones like daidzein, which in some people (only about 30–50%, depending on the population) can be converted by gut bacteria into Equol, a compound that binds more selectively to estrogen receptor beta (ER-β), which is believed to be protective and more relevant for menopause symptoms.
This means that two women eating the same amount of soy could have very different outcomes, depending on whether they are “equol-producers.” Most clinical studies don't screen for this, which could be a key reason why some trials show benefit while others don’t.
That’s why Equol supplements (which provide the metabolite directly, bypassing the need for gut conversion) are emerging as a promising option. Some well-designed RCTs have shown that Equol supplementation can significantly reduce hot flashes and improve mood and sleep in postmenopausal women, especially in those who are not naturally equol-producers.
I’m not sure the data on Equol supplements is that good based on the quality of the studies. But I’m going to be taking a morning depth look and will be posting about it.
There is some evidence suggesting diet affects how much equol an individual is able to produce; specifically vegetarians seem to produce more than non-vegetarians: https://pubmed.ncbi.nlm.nih.gov/16857839/
As a former vegan I would also caution any perimenopausal woman trying out a vegan diet. The B12 and iron loss from avoiding animal products can be significant and if you're heavy bleeder it can be a recipe for disaster. It can be done but requires much attention.
I don’t know how accurate that is. My son was in soy formula and I crushed his thyroid medication in that and his levels were just fine. But that is my n of 1.
Aside from all the points you make, this was a 12 week study which immediately disqualifies it. The placebo affect in VMS studies is significant and therefore requires a longer trial. Every study that shows black cohosh works is less
than 4 months. 52 week trial- no better than placebo. I honestly don’t know how this one made it through the review board.
I have changed so many things about my lifestyle. I’ve incorporated more plant-base meals, started running again (I was doing mostly strength before), started seeing a therapist and meditate and journal every day…. And all that did make me feel better. But what tipped the scale for me was cutting out alcohol completely. I haven’t had a hot flash since (im 49 and was a mostly 1-4 drinks on weekend or holiday nights drinker). I had night sweats every time the darned stuff touched my lips, regardless of amount. But I’m still doing all the other things too. Maybe it was a cumulative thing. 🤣
I am still asking the questions:
1. Does soy have the same mechanism of action as estrogen supplements tho perhaps less so?
2. If yes, then isn’t the risk of taking soy similar to taking estrogen?
3. Should women diagnosed with estrogen receptor breast cancer avoid soy?
I'll addressing that in a follow up post, but there is no data that shows that a moderate amount of soy is harmful for women who have had breast cancer.
A few more: do phytoestrogen molecules break down in digestion? How easily are they absorbed by the digestive system? Does cooking affect amounts in food (is raw tofu in a smoothie providing more than cooked in a stir fry?)
Thank you. I look forward to reading more from you on this topic.
Great questions!
1. Yes, soy works via estrogen receptors but much more weakly than estrogen itself. Isoflavones (the phytoestrogens in soy) preferentially bind to ER-beta, which is considered more protective, unlike ER-alpha, which is more active in breast and uterine tissue. So the action is estrogen-like, but more selective and weaker.
2. Because of this, soy doesn’t carry the same risks as hormone therapy. In fact, it can block stronger estrogens in some tissues.
3. For women with ER+ breast cancer, most studies show that soy foods are safe and may even lower recurrence risk.
As always, it’s best to talk to your doctor, but the science around soy is more reassuring than many realize.
A+ answer - thank you!
Thank you! I have asked multiple doctors and no one has had a good answer. Not can I find much in the medical literature.
Breast oncologists used to prohibit soy products, but it seems that phytoestrogens work more like a SERM than actual estrogens. So, thr no soy thing is no longer true for women with breast cancer.
I think the whole a dding soy to diet came about because japanese and chinese women who follow a traditional diet are reported to have less hit flashes and a lower incidence of breast cancer. However, these women grow up eating soyfoods and don’t them as an adult. There may be an entirely different mechanism at work.
Thank you for taking the time to dissect the evidence. One thing I’d add, especially when it comes to soy and vasomotor symptoms, is that the individual ability to metabolize soy isoflavones into equol may explain a lot of the conflicting results across studies.
Soy contains isoflavones like daidzein, which in some people (only about 30–50%, depending on the population) can be converted by gut bacteria into Equol, a compound that binds more selectively to estrogen receptor beta (ER-β), which is believed to be protective and more relevant for menopause symptoms.
This means that two women eating the same amount of soy could have very different outcomes, depending on whether they are “equol-producers.” Most clinical studies don't screen for this, which could be a key reason why some trials show benefit while others don’t.
That’s why Equol supplements (which provide the metabolite directly, bypassing the need for gut conversion) are emerging as a promising option. Some well-designed RCTs have shown that Equol supplementation can significantly reduce hot flashes and improve mood and sleep in postmenopausal women, especially in those who are not naturally equol-producers.
Looking forward to your next posts!
I’m not sure the data on Equol supplements is that good based on the quality of the studies. But I’m going to be taking a morning depth look and will be posting about it.
There is some evidence suggesting diet affects how much equol an individual is able to produce; specifically vegetarians seem to produce more than non-vegetarians: https://pubmed.ncbi.nlm.nih.gov/16857839/
As a former vegan I would also caution any perimenopausal woman trying out a vegan diet. The B12 and iron loss from avoiding animal products can be significant and if you're heavy bleeder it can be a recipe for disaster. It can be done but requires much attention.
Thank u for your thorough work in evaluating the study. It’s much appreciated.
I'd seen a report of that study and was curious about it. Thanks for the deep dive.
I read every so often that eating soy within (?)~10 hrs of taking levothyroxine decreases absorption. Is this really true? Sounds hoakie to me...
I don’t know how accurate that is. My son was in soy formula and I crushed his thyroid medication in that and his levels were just fine. But that is my n of 1.