Endometriosis & Soy Products

Bowl of soy beans in the pod

Here we go again, inspired to write due to a dietary “restriction.”  I’ve read that as an Endo Sufferer, I should avoid (or drastically cut back from) soy and soy-based products.  I’ve read soy mimics and increases estrogen levels, which we’ve come to understand can affect our Endometriosis growth and symptoms.  So today, I want to do my own research.

Soy products are the “richest sources of isoflavones” that humans can eat.  What the heck is an isoflavone? It’s a “plant-based compound with estrogenic activity” English, Lisa, ENGLISH! It means it’s a plant-based compound that mimics estrogen.  So, soy has a very rich, or high levels, of a property, a compound, a thing…that acts like, or mimics, estrogen.  The isoflavones can attach themselves to estrogen receptors throughout the body, and either mimic or block certain estrogen effects in tissues.

Why is that bad? Well, it’s not, for everyone.  Estrogen may help prevent certain forms of cancer (breast, uterine, or prostrate), stimulate bone growth, or help women suffering with post-menopausal symptoms. But for those of us who suffer from what very-well may be an estrogen-driven disease, it can be very bad.

Endometriosis & Soy

A 2001 study suggested that an increased intake of soy by Japanese women may lead to diseases which may require pre-menopausal hysterectomies, such as Endometriosis.

A study published in 2006 studied a 75-year-old woman who developed a tumor and continued Endometriosis symptoms.  She had a total hysterectomy 30 years prior and had been taking concentrated soy isoflavone supplements as part of her hormone replacement therapy for the past five years.  It stated, “[o]ur data suggest that phytoestrogens at least in concentrated form may play a role not only in maintenance of endometriosis but also in its malignant transformation.”  More studies are needed.

A study in 2008 followed three women who were taking soy supplements and suffered from various reproductive issues, including Endometriosis.  All three women reported a reduction of symptoms after they removed soy from their diets.

Soy also contains high levels of phytic acid, which may cause digestive issues and block mineral absorption.  Why do I say “may?”  Because there are a lot of opposing views on this topic online, whether they be studies, blogs, or corporate pages.  Don’t get me wrong : phytic acid has been shown to contain a lot of healthy properties as well.  But when our bodies are already working on overtime due to chronic inflammation, do we really want to tax it further with mineral deficiencies?

Today’s Soy Crops

There is a lot of uproar and concern over genetically modified crops. But what is a genetically modified organism (aka GMO)?  We’ve all heard about it in the news, read the labels, etc.

The European Union defines a GMO as “[a]n organism is “genetically modified”, if its genetic material has been changed in a way that does not occur under natural conditions through cross-breeding or natural recombination.”

The U.S. Food & Drug Administration defines “genetically engineered” products as, “[g]enetic engineering is the name for certain methods that scientists use to introduce new traits or characteristics to an organism.”  Although the F.D.A. insists that genetically modified crops are safe to consume, there is a lot of concern by the general public of their long-term effects.

The Non-GMO Project defines GMOs as “GMOs (or ‘genetically modified organisms’) are organisms whose genetic material has been artificially manipulated in a laboratory through genetic engineering, or GE. This relatively new science creates unstable combinations of plant, animal, bacteria and viral genes that do not occur in nature or through traditional crossbreeding methods.”

In 1996, the first genetically modified crop of soybeans was planted in the United States.  In 2007, approximately 57% of the world’s soybean crops were genetically modified, over 9 countries, and consuming 60 million hectares of land (that’s approximately 148,263,228 acres!).  Since 2012, 94% of the soybeans grown in the United States are genetically modified to be herbicide-tolerant; they can survive pesticides which kill weeds and insects in the agricultural field.

A 2003 study focused on genetically engineered or modified soybeans and reducing allergens, such as eliminating pollen allergens by using gene suppression techniques.

Are GMOs harmful? Depends on who you ask. Our government says it’s perfectly safe.  Other organizations say they are harmful.  Do you own research; formulate your own opinion.

Drug Interactions and Soy

Certain drugs have been known to interact with soy products.  Certain tumor-treating drugs (Nolvadex, Tamoxifen, or other Selective Estrogen Receptor Modulators) may be less-effective for people who have a high diet of soy-based products.  Studies have shown a decrease of efficiency in animal studies; however, further human studies need to be conducted.  It may also have a decreased affect on people taking Warfarin, a blood clot medication.  For people suffering from hypotyroidism (which is about 42-54% of Endometriosis sufferers), studies have also shown that the dosage of Levothyroxine needed to be increased for people consuming soy-based products, otherwise the thyroid hormone levels were abnormal and the medication was less-effective.

Foods Containing Soy

This is a limited list, but food and beverages that contain soy are: edamame, miso soup, natto, soy cheese, soy meats, soy milk, soy sauce, soy yogurt, tamari sauce, tempeh, and tofu.

Many other foods contain similar isoflavones.  In 2008, the U.S.D.A. put out a report of the isoflavone content of various foods.  You’re welcome to read their report and endless tables (if you dare).  As a quick comparison, look at the content of total isoflavones found in raw edamame (48.95mg/100g), raw potatoes (0.01mg/100g), almonds (0.01mg/100g), and canned tuna (0.28mg/100g).  The Top 10 winners of the most isoflavones content on this 2008 database were:

1. soy meal (209.58mg/100g)

2. soymilk film (196.05mg/100g)

3. soy flour (ranging from 178.10 – 150.94mg/100g)

4. soybean seeds, raw (154.53mg/100g)

5. roasted soy nuts (148.50mg/100g)

6. soy flakes (131.53mg/100g)

7. bacon bits, meatless (118.50mg/100g)

8. soy protein (ranging from 94.65-81.65mg/100g)

9. Kellog’s Smart Start with soy protein (93.90mg/100g)

10. tofu (ranging from 83.20-29.24mg/100g)

Some honorable mentions include:

1. infant formulas, various (ranging from 28.01-25.00mg/100g)

2. red clover (21.00mg/100g)

3. Kellogg’s Kashi Go Lean (17.40mg/100g)

4. Jack in the Box Monster Beef Taco (15.90mg/100g)

5. McDonald’s Cinnamon Roll (6.00mg/100g)

6. Subway Meatball Sandwich (6.00mg/100g)

7. Tigers Milk Protein bar (11.50mg/100g)

8. Cliff bar, energy bar (ranging from 26.90-17.70mg/100g)

On the Flip Side

There is always the “other view” on issues such as these.

A 2007 study found that Japanese women consuming soy products have a reduced risk of developing endometriosis.

Dr. Andrew Weil, a well-respected medical blogger, suggests eating soy-based products due to their health benefits; however, discourages the use of concentrated soy isoflavone supplements and “designer foods” containing soy isoflavones.

The question of the Hour

What will you do…for you; for your Endometriosis?  The one thing I will say to influence your decision : talk to your physician or nutritionist before deciding…

What have I done?  Drastically reduced the amount of soy I consume.  I used to eat edamame several times a week, so I’ve completely cut that out of my diet.  I’ve swapped soy sauce for tamari sauce, which is a fermented and gluten-free version of soy sauce.  I avoid soy-based protein shakes or milks and now consume coconut milk and a brown rice-based protein shake.  I really don’t feel like I’m missing out on much.  But do feel good for cutting back on increasing any additional estrogen levels within my body.

Again, anything I can do to help my body fight the further progression of Endometriosis is worth it to me.

(Updated March 27, 2019)


Dr. Weil

New York Times : (Article) 2014 – A Lonely Quest for Facts on Genetically Modified Crops

Oregon State University

Oxford Journals : (Article) 2003 – Genetically Modified Soybeans and Food Allergies



The Non-GMO Project


United States Department of Agriculture

United States Department of Agriculture Economic Research Service

United States Food and Drug Administration

Complementary Therapies in Clinical Practice : (Abstract) 2008 – Adverse Effects of Phytoestrogens on Reproductive Health : a Report of Three Cases

Epidemiology : (Abstract) 2007 – Effect of Soy Isoflavones on Endometriosis : Interaction of Estrogen Receptor 2 Gene Polymorphism

Critical Reviews in Food Science and Nutrition : (Abstract) 1995 – Phytic Acid: Healthy in Health and Disease

European Journal of Clinical Nutrition : (Abstract) 2001 – Soy Product Intake and Premenopausal Hysterectomy in a Follow-up Study of Japanese Women

The American Journal of Clinical Nutrition : (Abstract) 1992 – Soy Protein, Phytate, and Iron Absorption in Humans

~ Again, I am a layman.  I do not hold any college degrees, nor mastery of knowledge.  Please take what I say with a grain of salt.  If curious, do your own research 😉 Validate my writings.  Or challenge them.  And ALWAYS feel free to consult with your physician. Always.  Yours ~ Lisa

5 thoughts on “Endometriosis & Soy Products

  1. GMO aside, the latest tranch of research suggests that soya is neutral to slightly positive for endo in that weak phyto Oestrogen taking up space that a strong natural oestrogen would otherwise given there is a limited number of receptors, so i think your other side of the debate section needs strengthen and updating for a balanced post. I always eat organic traced soya by premium brands. If you want to avoid GM soy you also need to cut out esting meat and dairy from the animals that are fed on the GM soya
    Some people are of course​ intolerant as they may be to casein or lactose in milk or nuts or gluten and there is a propensity for allergies and intolerances in the Endo population.

    Liked by 1 person

  2. Research has shown that the phytoestrogens of soybeans connect to the oestrogen receptors and thus block them. The real oestrogen that’s being produced buy our own bodies is much more aggressive then the phytoestrogen of soybeans. It could well be that blocking the receptors with phytoestrogens will briefly lead to an increase of oestrogen in our blood. However, our body seems to be so smart to notice that there is an excess of oestrogen in the blood and will reduce the production of further oestrogen to balance the oestrogen level. The excessive oestrogen must of course be eliminated. Therefore the strengthening of the liver is of greatest importance since it is the liver which takes care of excessive oestrogen in our body. What do you think about this? At the same time I think it would be most important to avoid GMO soybeans and to eat only organic soy beans and not artificially produced extracts from soybeans. I would also avoid all wheat products and milk.


  3. Everytime I ate soy or soy products, my endo became worse. (What I eat including soy is always organic. So soy actually is harmful to some women like me!!)


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