(Post updated 02-02-26)
Ask someone for their opinion on the healthfulness of soy, and you tend to get one of two answers: it’s a nutritious superfood we should all be eating, or it’s a poison that causes hormonal havoc.
PROTECTIVE BENEFITS OF SOY
Soy is a nutrient-dense, whole plant food that offers a rare combination of high-quality protein, heart-healthy fats, fiber, and protective phytochemicals. Regularly eating whole soy foods such as tofu, tempeh, edamame, and soy milk has been linked to lower LDL cholesterol, improved lipid profiles, and better cardiometabolic health.
Soy’s naturally occurring isoflavones act differently than human estrogen and are associated with reduced risk of hormone-related cancers. They also improve breast cancer survival. Soy provides important minerals (iron, potassium, magnesium, and calcium when calcium-set, meaning a calcium-based compound was used to coagulate the tofu.
When enjoyed in minimally processed forms, soy is a versatile, affordable staple that supports overall health while fitting seamlessly into a whole-food, plant-based pattern.
However, don't take my word for it. Read on to discover the concerns over soy...
The Kind of Soy Makes a Difference
Soy comes in many forms for consumption. There are cooked beans called edamame, which are either in their pods or shucked and usually found frozen.
There’s minimally processed soy in the form of soy milk, tofu, and tempeh. Tempeh is a soybean “cake” produced by fermenting the beans. Other fermented products that contain soy are miso and natto.
Lastly, there are more processed versions, such as soy sauce, soybean oil, soy protein powder, and soy protein isolates, which are sometimes used to add protein to various foods and are often used in fake meats. Some of these are GMO, and some are not.
Let’s examine the other truths about the safety of soy to determine which you should and should not eat.
Claims and The Truth About Eating Soy
One of the most common claims about soy is that it has a negative effect on hormones.
HORMONE CLAIM #1 – The phytoestrogens in soy increase your risk of breast cancer.
RESPONSE: While it’s true that soy contains phytoestrogens, phytoestrogens are natural compounds that are structurally similar to estrogen, but they are NOT human estrogen. The good news is that these compounds are antiestrogenic, meaning they block estrogen's effects.
Recent research continues to support the safety and potential benefits of soy consumption for breast cancer survivors. A 2024 meta-analysis published in JNCI Cancer Spectrum found that soy isoflavones are associated with a 26% reduced risk of breast cancer recurrence, particularly among post-menopausal women.
Extensive human research shows that eating soy foods does not increase the risk of breast cancer or other cancers — in many studies, it’s linked with lower risk and improved survival. These benefits are strongest with whole soy foods rather than isolated soy supplements.
Dr. Greger provides more detailed information in his article, "How Phytoestrogens Can Have Anti-Estrogenic Effects."
Other foods, including animal products such as milk, eggs, meat, and fish, also contain phytoestrogens.
HORMONE CLAIM #2 – Soy disrupts the production of thyroid hormones
RESPONSE: Soy contains goitrogens, as do other foods to a lesser degree, such as broccoli, kale, peanuts, strawberries, and other vegetables. For those with hypothyroidism, this can make it more difficult for the thyroid to create its hormones. However, that depends on how it’s prepared.
Soy does not significantly affect thyroid hormone levels in most people, but it can reduce the absorption of thyroid medications if taken simultaneously. Adequate iodine intake helps minimize any goitrogenic concerns.
Iodine deficiency (more common in certain populations) could make someone more sensitive to goitrogens in soy. However, including iodine-rich foods such as seaweed or using iodized salt can help mitigate this risk for those concerned about thyroid health.
Soy is unlikely to have any adverse effects on the thyroid in healthy individuals. According to Dr. Joel Fuhrman, "Patients with diagnosed hypothyroidism may require a dosage adjustment to their thyroid medication to accommodate high soy intake because soy may decrease the absorption of the drug; however, this does not require avoiding soy."15
It’s not necessary to cut out a whole group of potentially healthy, nutritious foods from your diet.
If you do have a problem, eat fermented, cultured, or otherwise “aged” soybean products such as tempeh, soy sauce, miso, and natto. Cooking also helps.
HORMONE CLAIM #3 – Soy reduces testosterone levels in men, giving them feminine qualities.
RESPONSE: This claim has been disputed with clinical evidence. This evidence suggests that soy isoflavones do not affect male fertility.
Large human studies show no significant effect on testosterone or male reproductive hormones from typical soy consumption
Some data show that soy consumption by men can lead to a lower risk of prostate cancer later in life.
It’s easy to forget that the majority of GMO soy crops are fed to farm animals, which are then consumed.
For more information on these claims, the article "Free From Harm" is a valuable resource.
TAKEAWAY: Consumption of minimally processed soy is safe and likely protective in many cases.
The other claims center around the idea that soy contains toxins.
Another common argument against soy is that it contains toxins and “anti-nutrients” which can lead to digestive issues and nutrient deficiencies. The compounds people are referring to are phytic acids/phytates, trypsin inhibitors, and lectins.
Here’s a breakdown:
Anti-Nutrient/TOXIN CLAIM #1 - Phytic acid/phytates can bind to minerals in the digestive system, making them less available for absorption.
RESPONSE: Phytic acid/phytates are simply stored phosphorus and are commonly found in whole grains, legumes, nuts, and seeds. While it’s true that phytates can bind to minerals, you simply need to cook your beans and eat more mineral absorption enhancers, such as garlic and onions, to negate this effect.
Soaking, sprouting, or fermenting these foods will also significantly reduce their phytic acid levels. For an in-depth look at phytic acid and phytates, visit nutritionfacts.org for information and videos.
Phytates possess a wide range of health-promoting properties, including anti-cancer activity and the prevention of osteoporosis through improved bone density.
Anti-Nutrient/TOXIN CLAIM #2 - Trypsin inhibitors can affect protein digestion.
RESPONSE: Trypsin inhibitors are compounds that inhibit trypsin, an enzyme essential for the proper digestion of protein. Approximately 90% of the trypsin activity is destroyed by thorough cooking. Also, fermentation in miso and soy sauce deactivates the majority of anti-nutrients.
Anti-Nutrient/TOXIN CLAIM #3 - Lectins can be toxic and may cause allergies or inflammation.
RESPONSE: Lectins are another type of protein found in many commonly consumed foods, including tomatoes, peas, avocados, cabbage, carrots, raspberries, grains, legumes, nuts, and seeds, as well as dairy products.
Unfortunately, the subject of lectins has become controversial. If you're concerned, check out my article, Lectins in Beans: Good or Bad?
Soaking and cooking beans, which is how most of us prepare beans, will eliminate a significant amount of lectins, reducing the likelihood of any digestive upset.
TAKEAWAY: Almost all of us eat our soybeans cooked, which removes anti-nutrients. They are unlikely to pose a health risk and, in fact, can contribute to a longer lifespan. The longest-lived people in the world have beans, including soy, as the cornerstone of their diet.
Essential Amino Acids
Soybeans contain all of the essential amino acids (proteins) our bodies need. We must get these from food. Plus, soybeans are high in fiber, protein, vitamins, minerals, and a variety of phytochemicals and active compounds
- B Vitamins
- Vitamin C
- Potassium
- Magnesium
- Calcium
- Iron
- Zinc
- Manganese
- Phosphorus
- Copper
Minimally processed soy has a protective effect. Studies have shown that the compounds in soy may lower the risk of some cancers, including breast cancer, colon cancer, and prostate cancer. Soy may lower cholesterol and affect blood glucose levels.
CONCLUSION: Go Forth and Enjoy Soy!
Simply put, the fear of soy's dangers has been greatly exaggerated. If there is any caution with soy, it’s to enjoy it in moderation (as with most other foods!) and consume a variety of plant protein sources as well.
The best practice is to eat no more than 3-5 servings per day of minimally processed soy foods, such as cooked soybeans, tofu, tempeh, or soy milk. Watch the 1 1/2 minute video below from nutritionfacts.org (Dr. Greger) on his recommended intake of soy.
One serving of soy equals 1 cup of soy milk, 1/2 cup of tofu, tempeh, soybeans, or 1/3 cup of soy nuts.
Do not eat highly processed soy, such as in soy protein powder or some fake meats (check ingredients for “soy protein isolates” or TVP, “texturized vegetable protein.”)
Incorporating foods that contain soy into your diet has many health benefits, especially if you’re eating a plant-based diet.
Here are a few soy foods to get you started:
Edamame (fresh soybeans): Usually available frozen in the pod or frozen, shelled and ready to heat.
Soy milk from EdenSoy, Westlife, or Trader Joe’s Brand: made with soybeans and water ONLY.
Non-GMO Organic Tofu, including, but not limited to these brands: Nasoyu, House Foods, Westsoy, Trader Joe’s (not labeled as non-GMO, but it is). Also, Organic Silken Tofu. It’s safest to see this label on products.
Tempeh & Premade Products such as sausages, deli meats, etc., without soy protein isolates: Tofurky brand, Field Roast, WildWood, LightLife brand, and more. See a complete list here at nongmoproject.org.
References:
-https://www.drfuhrman.com/blog/127/dont-fall-for-the-myths-about-soy
-http://nutritionfacts.org/video/phytates-for-the-prevention-of-osteoporosis/
-http://www.edenfoods.com/articles/view.php?articles_id=80
-http://nutritionfacts.org/video/how-much-soy-is-too-much/
-https://www.womentowomen.com/thyroid-health/goitrogens-and-thyroid-health-the-good-news/
-http://www.aicr.org/foods-that-fight-cancer/soy.html
I have a problem with soy, my ‘inners’ don’t like soy. I have IBS, diverticulosis, lactose intolerant and have had pre-cancerous polyps, so being nice to my intestines is important. What can be substituted for soy in recipes. I do use a lot of beans and rice for my protein and have no problem digesting them.
Thanks for any help you can give and am waiting to have you new book sent as soon as it’s out from Amazon!
Kim
Hi Kim, I’m sorry that you’re having issues with soy. Substituting with soy is really on a recipe-by-recipe basis. Sometimes you can just leave it out and other times, you’d definitely need a substitute or a recipe might not even work with a substitute. If a recipe uses tofu as an addition, in say my Pineapple Fried Rice recipe, you could substitute another bean such as chickpeas, protein-rich seitan, use mushrooms or leave it out altogether. Unfortunately, it’s much harder to substitute if tofu is an integral part. I have seen a soy-free tofu called Pumfu that’s made with pumpkin seeds. It’s 320 calories for a 4-ounce serving. I haven’t tried it but it might work for you. Let me know if you try it. If it’s a creaminess that tofu is lending to a recipe, you could possibly substitute with cannellini beans, cashew cream made with raw cashews, vegan ricotta, or vegan sour cream. Of course, there are many soy milk alternatives that usually work quite well in a recipe. Your question is great and I think I’ll write an article about this so others can benefit, as well. 🙂