Who Shouldn’t Eat Soy?

How can soy foods have it both ways, pro-estrogenic effects in some organs (protecting bones and reducing hot flash symptoms) but anti-estrogenic effects in others (protecting against breast and endometrial cancer)?

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But what if you’re at high risk for breast cancer? See BRCA Breast Cancer Genes and Soy (

But what if you have breast cancer already? See Breast Cancer Survival and Soy (

What about genetically modified soy? See GMO Soy and Breast Cancer (

Not all phytoestrogens are beneficial, though. See What are the Effects of the Hops Phytoestrogen in Beer? (

How deleterious is hormone replacement therapy? See my video How Did Doctors Not Know About the Risks of Hormone Therapy? (

Synthetic estrogens used in livestock are also a concern. Check out Zeranol Use in Meat and Breast Cancer (

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Thanks for watching. I hope you’ll join in the evidence-based nutrition revolution!
-Michael Greger, MD FACLM

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  1. Ok. But can soy cause early puberty in girls?
    I keep hearing this rumor. I’d like to know the truth. Do you have a video about this issue?
    Thank you 😊

  2. I want to say something about the whole "soy boy" myth:

    Are you worried about "phytoestrogens?" Okay… scientists are at work on that. They'll get back to us when they have an answer. There is some evidence that too much soy can mess with your thyroid. But making you less of a man (smaller penis, mantits, etc.). Probably not.

    Even if so, many of these same people who push this "soy boy" crap seem to worry little about the REAL ESTROGEN in beef. Big Ag pumps what is essentially birth control (female hormones, estrogen) into beef and you consume it every time you eat beef, cheese, or drink milk. Real estrogen does the very thing "soy boy" pushers worry about.

    As far as we can tell, soy boys can actually have more testosterone. This may be because the beef-eaters have more estrogen in their systems than soy boys, which has an effect of cutting down testosterone. But "phytoestrogens" don't appear to have this effect. How ironic.

    For evidence, look at the study "Hormones and diet: low insulin-like growth factor-I but

    normal bioavailable androgens in vegan men," by "NE Allen, PN Appleby, GK Davey, and TJ Key," which is available on the website of the NIH.

  3. Hi! I am writing a paper for medical school and I really want to use the graph that was in this video from Mueller et al. However, in the original study, the graph is more complex. Did you simplify the graph yourself, or is there a place that I can obtain the simplified graph?

  4. Thumbs down for click bait title. You didn't answer the question. Merely touched on it as an afterthought. You mentioned those with allergies, but not any other conditions, like hypo- or hyper- thyroid. I've "heard" those with thyroid issues should avoid soy, but it was not from people with medical or scientific backgrounds. And no doctor has addressed this question fully. Merely glossed over it. Leaving me highly dissatisfied.

  5. I watched this video to see if it was good to take protein powder no gmo daily 30 grams in my breakfast, until the end of the video disappointed me.

  6. can anyone explain why dr. mcdougall is against soy products saying, "Why you might not want to consume isolated soy products! In this audio excerpt Dr John McDougall explains the connection between these soy products and increasing IGF-1 levels. When you raise your IGF-1 levels you greatly increase your risk of cancer.

  7. Soy is not health, it is only health when fermented and organic, but it still blocks many nutrients from entering our bodies. It needs to be fermented in order to stop this from happening.
    The soy nowadays is gm based soy. It has been formulated to stop the soy plant from dying when sprayed with weed killers. If the plant is safe, then these chemicals with do the damage.

  8. Thank you for that fine information. I was hoping you would address the effects of soy and breast cancer. I have read a couple of studies that said soy is an estrogen mimicker and may set women up for increased risk for breast breast cancer. I’d love to hear your thoughts on this. Thanks you.

  9. Isn't the estrogenic effects of soy supposed to be not so good for males as it can fuck with their estrogen/testosterone balance?

  10. Dr. McDougal has a vid out that says that 40 grams of soy protein/day
    increases Insulin Life Growth factor 70%. Does Dr. Greger address this?

  11. I supposedly had a soy allergy when I was tested as a kid… but I ate soy products anyway (it's in so many things) and over time I lost faith in the accuracy of the allergy test since I've never had a reaction.

  12. I was just wondering does the High Levels of Magnesium contribute to the Higher Bone Densities in those who consume Soy Products? Isn't there a correlations to those who eat Mag-Rich foods?

  13. Excellent review! I eat anywhere between 250 to 500 mg of soy phytoestrogens per day, and even my multivitamin pills contain 40 mg of soy phytoestrogens. I also take probiotic pills containing the proper bacteria strains that convert daidzein into (S)-Equol (which is a metabolite of daidzein with the highest "estrogenicity" of all phytoestrogens. Indeed, I've been trying to explain this topic to mainstream anti-intellectuals and iGnorant iDiots for years now, that soy phytoestrogens are good for both men and women alike, because they're SERMs-like molecules, not actual estrogens. Mainstream thinkers however, don't understand what the hell a SERM is, so there's always that cognitive dissonance. Anyway keep up the good work.

  14. You should have been a voice over actor. You have a cool and persuasive voice. If they ever do an animated version of the X Files, you would be perfect for Mulder.

  15. This is good to know since I have a genetic illness called hypermobility syndrome EDS and at the age of 26, my bone mass is already low and doctors said I’m gonna get worse and there is nothing I can do to stop it but I refuse to believe it. Yes, there is no cure for me but I believe that a healthy diet along with my strength training workouts, can help manage my health in the long run.

  16. For years I have been consuming whole milk , now after being more inform and educated I'll start consuming more almond and soy milk .

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