Endometriosis is a chronic condition affecting millions of women worldwide, characterized by the growth of endometrial tissue (which normally lines the uterus) outside of the uterus. This condition can be extremely painful, lead to fertility issues, and cause a variety of uncomfortable digestive symptoms such as bloating, constipation, and food intolerances. One key factor in the progression of endometriosis is estrogen dominance, where estrogen levels in the body are higher than normal. This hormonal imbalance stimulates endometriosis tissue's growth, exacerbating the disease's symptoms.

As an endometriosis dietitian, I work closely with clients who are navigating the complex relationship between diet and symptom management. One food that often raises questions is soy—whether it exacerbates endometriosis or if it can be part of a healthy diet.

In this post, we'll explore the role of soy in the diet of women with endometriosis, reviewing its nutritional profile, the concerns surrounding its phytoestrogen content, and the current research on soy's impact on this condition.

Understanding Soy: A Nutritional Profile

Soy is a versatile plant-based protein source that is rich in nutrients, including:

• Protein: Soy is a complete protein containing all nine essential amino acids.

• Fiber: Soy is a good source of both soluble and insoluble fiber.

• Vitamins and minerals: Soy is a good source of vitamins B1, B2, B5, and B6, as well as iron, magnesium, and potassium.

Soy is a staple in many plant-based diets and is found in a variety of forms, including:

• Soybeans (whole or edamame)

• Tofu

• Tempeh

• Soy milk

• Soy protein products (like textured vegetable protein)

The presence of isoflavones in soy has led to concerns about their potential impact on estrogen levels and endometriosis. Some people believe that soy may worsen endometriosis by increasing estrogen levels, while others argue that it could help balance estrogen levels.

Isoflavones are a type of phytoestrogen—plant-derived compounds that have a chemical structure similar to human estrogen. The two primary isoflavones in soy are genistein and daidzein, which can weakly bind to estrogen receptors in the body. The binding to estrogen receptors is where the controversy arises regarding soy's potential impact on estrogen-sensitive conditions like endometriosis.

Research Overview on Soy and Endometriosis

Because soy contains phytoestrogens, some women with endometriosis avoid it out of fear that it could exacerbate their condition by increasing estrogen activity in the body. Estrogen dominance is a factor in endometriosis, and any compound that mimics or affects estrogen is subject to scrutiny.

Soy as a Potential Estrogen Balancer?

Interestingly, some research suggests that phytoestrogens in soy may not worsen estrogen-related conditions like endometriosis. Because these plant estrogens are much weaker than the body's estrogen, they may act as natural estrogen regulators. By binding to estrogen receptors, they might block the effects of more potent estrogens, potentially reducing the overall estrogen activity in the body. Thus, phytoestrogens may help alleviate estrogen dominance in some women.

A few studies support this. For instance:

• Youseflu et al. found that higher intake levels of isoflavones, lignans, and coumestrol (phytoestrogens) correlated with endometriosis risk. Women who consumed more of these compounds through dairy products and fruits had a lower risk of developing the condition.

• Tsuchiya et al. showed that urine levels of genistein and daidzein were inversely associated with the risk of advanced endometriosis, suggesting that these compounds might help suppress the progression of the disease but not early-stage endometriosis.

Does Soy Make Endometriosis Grow?

Some health professionals are cautious about recommending soy for women with endometriosis. The concern is that since soy contains compounds that mimic estrogen, it could stimulate estrogen receptors and exacerbate estrogen dominance, potentially worsening the growth of endometrial tissue. Anecdotal reports from some people suggest that eliminating soy from their diet has helped reduce symptoms like inflammation, bloating, and pain.

A study by Mumford et al. found no significant difference in phytoestrogen levels between women with and without endometriosis, suggesting that phytoestrogen intake does not play a clear role in preventing or progressing endometriosis.

Ultimately, more research on how soy intake affects endometriosis risk and progression.

Soy Intake and Symptom Management

For people with endometriosis, soy intake should depend on individual responses. Moderate soy consumption can offer benefits like improved heart health, a plant-based source of protein, and a rich supply of vitamins and minerals. Numerous clinical studies have found that daily consumption of up to 50g of soy protein per day is safe and may be beneficial for improving risk factors for chronic disease. 

Some women report that including soy in their diet has helped balance hormones and improve symptoms, while others find that it worsens bloating and pain. These anecdotal differences highlight the importance of personalized nutrition.

Other Dietary Considerations for Endometriosis

In addition to soy, other dietary changes can help manage endometriosis symptoms. Many women with the condition benefit from an anti-inflammatory diet, which includes foods like:

• Omega-3 rich fish (salmon, sardines)

• Leafy greens and colorful vegetables

• Whole grains

• Nuts and seeds

Every person's response to dietary changes will differ, so working with a healthcare provider is crucial for finding the best approach.

How to Incorporate Soy with Endometriosis

Including a moderate amount of soy in your diet may benefit your overall health. If you experience increased bloating, pain, or inflammatory symptoms with soy, getting protein from other sources may be a better option. Here are a few tips:

• Choose fermented soy products like tempeh or miso, which are easier to digest and contain beneficial probiotics.

• Stick to whole soy foods (like tofu, edamame, and soy milk) rather than highly processed soy products.

• Monitor your symptoms after consuming soy, and consult your healthcare provider if you notice any changes.

Conclusion

The relationship between soy and endometriosis is complex, with research offering mixed results. While some studies suggest that soy's phytoestrogens may help regulate estrogen levels and reduce the risk or progression of endometriosis, more research is needed.

Ultimately, the decision to include soy in your diet should be guided by how your body responds and your healthcare provider's advice. A personalized approach to nutrition, based on your symptoms and health goals, is key to managing endometriosis effectively.

References:

Bartiromo, L. et al. Endometriosis and Phytoestrogens: Friends or Foes? A Systematic Review. Nutrients, 2021. DOI: 10.3390/nu13082532.

Boutas I, Kontogeorgi A, Dimitrakakis C, Kalantaridou SN. Soy Isoflavones and Breast Cancer Risk: A Meta-analysis. In Vivo. 2022 Mar-Apr;36(2):556-562. doi: 10.21873/invivo.12737. PMID: 35241506; PMCID: PMC8931889.

Canivenc-Lavier MC, Bennetau-Pelissero C. Phytoestrogens and Health Effects. Nutrients. 2023 Jan 9;15(2):317. doi: 10.3390/nu15020317. PMID: 36678189; PMCID: PMC9864699.

Křížová L, Dadáková K, Kašparovská J, Kašparovský T. Isoflavones. Molecules. 2019 Mar 19;24(6):1076. doi: 10.3390/molecules24061076. PMID: 30893792; PMCID: PMC6470817.

OpenAI. (2024). ChatGPT (October 8 version) [Large language model]. Available from https://openai.com/chatgpt

Parazzini F, Viganò P, Candiani M, Fedele L. Diet and endometriosis risk: a literature review. Reprod Biomed Online. 2013 Apr;26(4):323-36. doi: 10.1016/j.rbmo.2012.12.011. Epub 2013 Jan 21. PMID: 23419794.

Setchell KD. Soy isoflavones--benefits and risks from nature's selective estrogen receptor modulators (SERMs). J Am Coll Nutr. 2001 Oct;20(5 Suppl):354S-362S; discussion 381S-383S. doi: 10.1080/07315724.2001.10719168. PMID: 11603644.