I have endometriosis, can I eat soy foods?

Soy is a type of legume native to East Asia that has been cultivated for thousands of years. It is a nutritious and versatile food, and it's one of the most widely consumed plant-based foods in the world, especially in vegetarian and vegan diets.

However, there is much debate on whether soy foods (also called soya foods) are good for certain health conditions, like endometriosis. If you have endometriosis, you might have come across the soy debate and find yourself asking: Will it make my symptoms worse? Will it make them better? Should I be avoiding soy foods with endometriosis altogether?

So, what does the  research actually say? In this blog post, I'll cover what soy foods are, the nutritional and health benefits of soy, the potential controversy between soy and endometriosis, and explore what the research says about soy and endometriosis.

What are Soy Foods?

Soy foods are made from the soybean, which is a cream coloured, oval bean, which is the size of a garden pea. Edamame are young soybeans harvested before they ripen or harden. Soy foods include products such as soy milk, tofu, tempeh, soy yoghurt, miso and soy sauce (1).

Soybeans are rich in protein, (containing eight essential amino acids), fibre, essential minerals, and polyunsaturated fats, making them a valuable source of nutrition. Most soy drinks are fortified to ensure they provide similar or higher levels of micronutrients typically found in dairy milk.

Health Benefits of Soy Foods

Soy is praised for its numerous health benefits, including:

• Heart Health: Soy foods have been shown to lower LDL cholesterol (the "bad" cholesterol) and may help reduce the risk of heart disease (2,3).

  
  

• Hormonal Balance: The isoflavones in soy may help reduce symptoms of menopause, such as hot flushes, and may play a role in balancing hormone levels (4).

Soy and Phytoestrogens

Soy and soy foods also contain polyphenols, which are antioxidants, that have anti-inflammatory benefits. Soybeans and soy foods contain a specific type of polyphenol, known as phytoestrogens, called isoflavones. You can find them in smaller amounts in other legumes and nuts. The most common isoflavones are genistein, daidzein, and glycitein.

Phytoestrogens and Endometriosis

Endometriosis is an oestrogen dependent condition, and women with endometriosis often have higher levels of oestrogen. High oestrogen levels have been linked to the

production of prostaglandins which are pro-inflammatory and can worsen endometriosis pain and bloating.

The controversy lies in the fact that the phytoestrogens (isoflavones) found in soy foods can have a similar structure to the female sex hormone oestrogen and can therefore mimic the effects of oestrogen in the body. Since phytoestrogens can bind to oestrogen receptors, the assumption is that they could signal the body to elevate oestrogen levels even further, thereby worsening endometriosis symptoms.

However, isoflavones have been found to have an anti-oestrogen effect when oestrogen levels are high in the body. It causes a protective effect where the isoflavones bind to the receptors that oestrogen would usually bind to, thereby blocking oestrogen’s effects. In other words, isoflavones can have a ‘normalising’ effect on oestrogen where they boost levels when they’re low and counteract levels when they’re too high. Therefore, phytoestrogens may help alleviate endometriosis symptoms (5).

One study, conducted in Japan, where soy is a common part of the diet, found that higher intakes of the phytoestrogens genistein and daidzein was associated with a decreased risk of advanced stage endometriosis amongst infertile women. The study also found an association between high intakes of soy phytoestrogens and a decreased severity in endometriosis symptoms. This was because the phytoestrogens had an anti-oestrogenic effect that blocked the body's own oestrogen from binding to receptors (6).

How Can I Include Soy in My Diet?

In addition to their protective benefits for various health conditions, soy and soy foods are highly nutrient-dense and are valuable additions to anyone's diet, particularly for those following a vegan, plant-based, or lactose-free lifestyle.

If you want to include soy in your diet while managing endometriosis, choose whole soy foods. Opt for minimally processed options like tofu, tempeh and edamame instead of processed soy products.

Phytoestrogens are abundant in many foods other than soy like nuts and seeds, pulses and grains. These foods are also a feature of the Mediterranean diet with many studies showing that women with endometriosis (who adopted this diet) had a significant improvement in pain symptoms. You can read more about this in my free Eating for Endo Ebook here.

Key Takeaways

While some concerns remain about the oestrogenic effects of soy, current research suggests that these effects are not likely to exacerbate endometriosis and may, in fact, provide symptom relief for some women. Unprocessed soy foods may offer benefits for women with endometriosis by helping to balance hormones and reduce inflammation.

As with any dietary change, it’s important to listen to your body and work with a Registered Dietitian. If you’re looking for some personalised support to manage your endometriosis, feel free to contact me to book your free 20-minute Discovery Call, or you can also email me here: laura@nurture-for-life.com

References

1. British Dietetic Association (2022). Food Fact Sheet: Soya foods and your health. Accessed: https://www.bda.uk.com/resource/soya-foods.html

2. Ramdath DD, Padhi EM, Sarfaraz S, Renwick S, Duncan AM. Beyond the cholesterol-lowering effect of soy protein: a review of the effects of dietary soy and its constituents on risk factors for cardiovascular disease. Nutrients. 2017 Dec;9(4):324.

3. Taku, K, Umegaki, K, Sato, Y (2007) Soy isoflavones lower serum total and LDL cholesterol in humans: a meta-analysis of 11 randomized controlled trials. American Journal of Clinical Nutrition, 85: 1148–1156.

4. Taku K. Extracted or synthesized soybean isoflavones and menopause hot flushes. Menopause. 2012;19(6):776-790.

5. Bartiromo L, Pinna G, Bini V, Fava V, De Tora L, Lamberti F, et al. Endometriosis and phytoestrogens: friends or foes? A systematic review. Nutrients. 2021 Aug;13(8):2532

6. Zhang Y, Liu Y, Zhou Y, Zhao M, Wu C, Liu J, et al. Effect of soy isoflavones on endometriosis: interaction with estrogen receptor 2 gene polymorphism. Epidemiology. 2007 May;18(3):402-8.