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 wreaks hormonal havoc.
The Kind of Soy Makes a Difference
Soy comes in many forms for consumption. There are the cooked beans called edamame, either in their pods or shucked, and usually found frozen.
There’s minimally process soy in the form of soy milk, tofu, and tempeh. Tempeh is a soybean “cake” that’s produced by fermenting the beans. Other fermented products that contain soy are miso and natto.
Lastly, there are the more processed versions such as soy sauce, soybean oil, soy protein powder, and soy protein isolates that are sometimes used in a variety of foods to add protein and are often in fake meats. Some of these are GMO and some are not.
Let’s take a closer look at the truths about the safety of soy to find out which of these you should and should not be eating.
The Truth About Eating Soy
One of the most common claims about soy is that it has a negative effect on hormones.
Claim #1 – The phytoestrogens in soy increase your risk of breast cancer.
While it’s true that soy contains phytoestrogens, phytoestrogens are simply natural compounds that are structurally similar to estrogen, they are NOT human estrogen. The good news is that these compounds are antiestrogenic, meaning they block the effects of estrogen.
Dr. Greger goes into more detail in his article, How Phytoestrogins Can Have Anti-Estrogenic Effects.
Other foods including animal sources such as milk products, eggs, meat, and fish also contain phytoestrogens.
Claim #2 – Soy disrupts the production of thyroid hormones
Soy contains goitrogens as do other foods to a lesser degree such as broccoli, kales, peanuts, strawberries, and other vegetables. For those with hypothyroidism, that can make it more difficult for the thyroid to create its hormones. However, that depends on how it’s prepared.
The truth is that soy is unlikely to have any thyroid effects on 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 helps, as well.
Claim #3 – Soy reduces testosterone levels in men, giving them feminine qualities.
Some data shows that soy consumption by men can lead to a lower risk for prostate cancer later in life.
It’s easy to forget that milk and meat from animals actually contain natural animal hormones and can be treated with synthetic growth hormones, as well. In addition, the majority of GMO soy crops are fed to farm animals which are then consumed.
For more on all of these claims, this article from Free From Harm is a great reference.
TAKEAWAY: Consumption of minimally processed soy is safe and likely protective in many cases.
Claim #4 - 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:
Claim #1 - Phytic acid/phytates can bind to minerals in the digestive system, making them less available for absorption.
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/phytates and their benefits, check out nutritionfacts.org information and videos on the subject.
Phytates have a wide range of health-promoting properties such as anti-cancer activity, osteoporosis prevention through improved bone density.
Claim #2 - Trypsin inhibitors can affect protein digestion.
Trypsin-inhibitors are compounds that inhibit trypsin - an enzyme needed to properly digest protein. Approximately 90% of the trypsin activity is destroyed by thorough cooking. Also, fermentation in the case of miso and soy sauce deactivates the majority of anti-nutrients.
Claim #3 - Lectins can be toxic and may cause allergies or inflammation.
Lectins are another protein that’s found in many commonly consumed foods such as tomatoes, peas, avocado, cabbage, carrots, raspberries, grains, legumes, nuts, and seeds as well as dairy.
Unfortunately, the subject of lectins has become controversial. If you're concerned, check out Dr.Michael Greger's article on the subject, "Art Lectins in Food Good or Bad for You?." in his article.
Soaking and cooking beans, which is how most of us prepare beans, will eliminate a significant amount of lectins, reducing the likeliness of any digestive upset.
TAKEAWAY: Almost all of us eat our soybeans cooked which removes these anti-nutrients. They are unlikely to pose a risk to health and in fact, can contribute to longevity. The longest-lived people in the world have beans, including soy, as the cornerstone of their diet.
PROTECTIVE BENEFITS OF SOY
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
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 and prostate. Soy may lower cholesterol and affect blood glucose levels.
CONCLUSION: Go Forth and Enjoy Soy!
Simply put, the fear of the dangers of soy 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. See this 1 1/2 minute video, below, from nutritionfacts.org (Dr. Greger) on how much soy he recommends.
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 to get you started:
Edamame (fresh soybeans): Usually available frozen in the pod or frozen shelled and ready to heat.
Soy milk from EdenSoy, Westsoy, or Traders 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 sausage, deli meats, etc without soy protein isolates: Tofurky brand, Field Roast, WildWood, LightLife brand, and more. See a complete list here at nongmoproject.org.