Dr. Oz on Soy

I have never watched the Dr. Oz show, but two days ago I got a phone call from my mother saying that Dr. Oz was telling people that processed soy can mess up your hormones.

Nerdles.com provides a run down on the show that includes:

“Now the #1 thing to avoid to keep your hormones in balance is processed soy. Processed soy is stripped of all the healthy omega-3s, fiber, and are ultimately left with carbs and soy protein isolate. Inside soy protein isolate, you’re finally left with estrogen and high-levels of this will interrupt your cycle….The gold standards of soy are miso, natto, and tempeh – get these into your diet instead for healthy hormone levels.”

But processed soy does not contain more isoflavones (the “soy estrogens”) per serving than unprocessed soy, so this doesn’t make much sense. Processing soy protein concentrates the protein, not the isoflavones.

And on Dr. Oz’s website, in the article, 4-Week Cyclical Hormonal Health Plan, they bring out the old Weston Price Foundation talking points, “Traditionally, Asian cultures consume no more than two teaspoons of fermented soy a day, which has been shown to be health-promoting, while more than that quantity becomes problematic.”

The idea that Asians limit their soy to two teaspoons a day, and that it is all fermented, is not backed up by the research as reviewed in my article, Soy: What’s the Harm? – Asian Intakes. By the way, two teaspoons of soy is only 1/12 of a typical 1/2 cup serving of tempeh – not even a serving per week.

Nor is there any evidence that more than two teaspoons a day is problematic. The entire article, Soy: What’s the Harm? is a discussion of how much soy is safe (or you can see the much abridged version, Response to Not Soy Fast).

Since I have not reviewed the large amount of research on soy and menstrual cycles in any rigorous way, I asked Dr. Mark Messina, one of the world’s leading soy experts, to comment on the statement that soy will interrupt your menstrual cycle and he said:

“Soyfoods and the phytoestrogens in soy have relatively minor effects on reproductive hormone levels in women. There is evidence indicating that soy may increase the length of the menstrual cycle by approximately one day. However, when only high-quality studies are considered, the effect of soy is no longer statistically significant. Whether a possible effect of soy on menstrual cycle length has clinical implications is unclear although longer cycles are associated with a lower risk of breast cancer.”

In addition to the information on soy, that entire article, 4-Week Cyclical Hormonal Health Plan, sounds pretty far-fetched.

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11 Responses to “Dr. Oz on Soy”

  1. Emily Says:

    Dr. Oz…Anything that he says I usually dismiss since much of what he promotes is pseudoscience and woo with exaggerating good science or having little to nothing to back up his claims. You know he’s gone over the edge when he supports complementary and alternative “medicine” and psychics.

  2. Maria B Says:

    Thanks as always for being the vegan voice of reason, Jack! I’ve found (through blood work done at regular intervals) that my own levels of estrogen have actually *decreased* since being vegan and my hormonal profile overall has greatly improved, and I eat 1-2 servings of soy a day. I definitely have not grown a third breast or little edamame-shaped horns last time I checked, which is what some of the “soy is poison” brigade would have us believe happens when you eat soy on the daily. This is just my experience, but I sure do get tired of negative, sweeping nutritional generalizations. Soy is not for everyone, but for many it makes being vegan a heck of a lot easier.

  3. Nadine Says:

    I stick with organic soy just because I don’t like the ecological implications of GMO soy. I’ll eat anywhere from 1-5 servings a day and have done so for 5+ years to no ill effect. In fact, I’ve found that it makes me feel satiated in a way that other plant milks or foods do not. I think it’s because of the higher protein content.

  4. Phred Says:

    Ask Dr. Messina how much money he gets from the soy industry.

  5. Jack Norris RD Says:


    That would be a tad rude. But, yes, Dr. Messina does get money from the soy industry. It’s hard to be an expert on soy without getting funding from somewhere – it’s not exactly something you can do in your spare time. My experience with Dr. Messina is that he is not shy about pointing out the research that has not been pro-soy and that he does not spin soy research.

    We all have to admit at least one thing about soy and it’s effects on humans – it certainly stirs people’s passions. 🙂

  6. Gail Legato Says:

    Here is my soy story: About 20 years ago I started drinking 4 oz of soy milk per day to relieve migraine headaches that appeared to be menstrual cycle related. It worked very well. So well, after many years headache free, I stopped drinking the soy, the headaches returned! I started back on the soy (different brand this time as my old brand tasted like cardboard and there were many new tasty brands), to my disappointment, there was no migraine relief this time. My daughter mentioned that soy is now genetically modified so perhaps the phytoestrogens are different now? Well I researched the different soy brands and switched to a non GMO brand and my headaches disappeared again! This experience sparked an interest in GMO’s and how food effects our body. Through my studies, this is the best analogy I have come across to explain plant phytoestrogens (many plants contain them, not just soy) and their role in our body: Our body produces it’s own estrogen, let’s think of it as a 747 airplane, and the plant ingested phytoestrogen as a small plane, your body is the runway. If there is even a small plane on the runway, the Big 747 coming in can’t land so the body stops producing extra 747 airplanes, hence the estrogen level produced by the body doesn’t increase to high levels each month, the plant phytoestrogens even though they are small, a daily dose, satisfies the body’s needs. No extra estrogen produced by my body each month so no migraine. The second interesting bit of knowledge I have come across about soy is relating to soy isolates. There was a peer reviewed scientific study done on milk protein isolates and it was found to be carcinogenic so milk protein isolates were soon replaced with soy isolates and no study has been done on it’s effects, but there is suspicion these highly processed isolates are not healthy. My thoughts, stay away from genetically modified and processed food of any kind. Enjoy whole non GMO plants, even soy!
    I am a plant based eater, a retired Medical Laboratory Technologist, still love to research and I am not connected with any food related organizations.

  7. Jack Norris RD Says:

    > My daughter mentioned that soy is now genetically modified so perhaps the phytoestrogens are different now?

    I haven’t seen anything suggesting this, though I’ve often wished we could get some strains of soy without isoflavones (and phytates) so that soy could cease being such an issue – at least for those who want the protein without the isoflavones.

    > There was a peer reviewed scientific study done on milk protein isolates and it was found to be carcinogenic so milk protein isolates were soon replaced with soy isolates and no study has been done on it’s effects, but there is suspicion these highly processed isolates are not healthy.

    Are you talking about Colin Campbell’s research as he described in The China Study? Our food supply has plenty of both milk protein isolates and soy protein isolates. And, yes, there are plenty of people who consider them to be unhealthy and a great deal of research trying to determine whether they are or not.

  8. lisa Says:

    Ha, I went vegan a few months ago and was basically menopausal — i din’t have a cylcle to mess with! I have used organic soy products, but not obsessively. Guess what? I now HAVE a cycle!!!

  9. Jack Norris RD Says:


    Are you saying that you didn’t have a cycle when you went vegan, or that you lost your cycle upon becoming vegan and then got it back after you added soy in? Some people might be more sensitive to soy isoflavones than others, but going vegan creates a lot of dietary changes and it could also be unrelated to diet.

  10. Ms Minhas Says:

    I’m not an expert by any means and I am aware that I was eating soy in excess which I believe has impacted my hormones negatively. I recently started to research it and find the information overwhelming as there is conflicting evidence. Most of what I have read seems to echo what is cited in this article re:soy protein isolate – http://www.prevention.com/food/healthy-eating-tips/how-healthy-soy-protein-isolate. (see below)

    [Reproduced article cut by me. – Jack]

    However agreeing with what is in the article is simply my opinion and gut instinct based on what I have experienced. I truly would love to think I was wrong as I like the Soy vegetarian products and used to be a strong advocate of Organic Soy products!

  11. Jack Norris RD Says:

    Ms Minhas,

    What were your negative hormone symptoms? Did they clear up upon eliminating processed soy?

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