The Controversy of Soy

Without a doubt, soy is one of the most controversial products on the planet. In fact, ask a handful of health experts “is soy bad for you?” and you’re likely to get a dozen different responses.

While some claim that it can disrupt hormone levels, tank thyroid health and contribute to cancer, others point out that it can improve heart health, boost fertility and keep cholesterol levels in check.

So is soy bad for you? And how much soy is too much? Keep reading for everything you need to know about the health effects of this incredibly common yet controversial ingredient.

Is soy bad for you? - Dr. Axe

What Is Soy?

The soybean is a type of legume that is originally native to East Asia, but is now grown and cultivated all around the globe.

Apart from the edible bean itself, the soybean plant is used to produce a number of different products, including soy milk and tofu. It’s also often fermented to produce ingredients like tempeh, soy sauce and miso, which is a traditional Japanese paste made from fermented soybeans.

Soybeans are used to make a variety of processed foods as well, including many vegan meat substitutes and dairy-free yogurts and cheeses. Other compounds such as soy lecithin and soy protein isolate are often extracted from the plant and added to processed foods and supplements.


Is Soy Bad for You?

Soybeans are one of the most controversial ingredients out there. In fact, it seems like nearly every week a new article is published promoting the dangers of soy, detailing the effects of soy on estrogen levels and hyping up the potential soy milk side effects in males.

Like most foods, there are both positive and negative aspects when it comes to soybeans, and some special considerations for those with specific health concerns. However, in moderation, many soy products can be enjoyed as part of a healthy diet.

Still, it’s best to select organic, fermented and minimally processed varieties and pair with a diverse range of other nutrient-dense foods to maximize the potential health benefits.


Soybeans are a great source of protein and provides an array of other important nutrients, including manganese, calcium and selenium.

For example, a half-cup serving of tofu contains the following ingredients:

  • 88 calories
  • 2 grams carbohydrates
  • 10 grams protein
  • 5.5 grams fat
  • 1 gram dietary fiber
  • 0.8 milligrams manganese (39 percent DV)
  • 253 milligrams calcium (25 percent DV)
  • 12.5 micrograms selenium (18 percent DV)
  • 152 milligrams phosphorus (15 percent DV)
  • 0.3 milligrams copper (13 percent DV)
  • 46.6 milligrams magnesium (12 percent DV)
  • 2 milligrams iron (11 percent DV)
  • 1 milligrams zinc (7 percent DV)
  • 23.9 milligrams folate (6 percent DV)

Each serving of tofu also contains some potassium, vitamin K, vitamin B6, thiamine and riboflavin.


Soybeans contain several powerful compounds that have been extensively studied for their beneficial effects on health, including isoflavones, plant sterols, prebiotics and more.

Some research has found that including plenty of soy foods in your diet may help manage cholesterol levels and promote better heart health. In a 2015 review published in British Journal of Nutrition, soy consumption was found to reduce levels of triglycerides, total cholesterol and bad LDL cholesterol while also boosting levels of beneficial HDL cholesterol.

It may also offer several health benefits for women specifically. In particular, isoflavones have been shown to increase levels of estradiol (estrogen) in the body, which can reduce certain side effects of menopause. In fact, one review of 19 studies found that isoflavone supplements were able to decrease the frequency and severity of hot flashes in women.

Soy protein could also promote regular menstrual cycles and enhance fertility. For example, one study out of Rome actually found that phytoestrogens helped increase the pregnancy rate among 213 women undergoing in vitro fertilization.

Plus, other studies have found that regular consumption of soy may also be tied to a lower risk of developing breast cancer, along with colorectal, prostate and lung cancer as well.

Risks and Side Effects

Although soy foods may be associated with several potential health benefits, there are a few side effects and risks that need to be considered as well.

For starters, isoflavones act as phytoestrogens, meaning that they mimic the effects of estrogen in the body. For this reason, many people choose to avoid soy foods due to concerns about their effect on hormone-linked cancers, such as breast cancer.

Interestingly enough, however some studies have actually found that soy isoflavones could actually be linked to a lower risk of developing breast cancer. According to one 2016 review, higher consumption of soy products was linked to a 30 percent lower risk of developing breast cancer among Asian women.

Of course, it’s important to note that these populations typically consume non-GMO, fermented and minimally processed soy foods, which is a stark contrast to many of the highly processed products consumed in most western countries.

Because of the phytoestrogen effects of soybeans, many also wonder: Is soy bad for men? Studies have turned up mixed results on the impact of soy consumption on hormone levels for men.

For instance, one animal model published in the Journal of Endocrinology found that administering high amounts of soy phytoestrogens to rats reduced testosterone levels and prostate weight within five weeks. On the other hand, a large review in 2010 showed that consuming soy had no effect on hormone levels in men, and other studies have actually found that soy consumption may be associated with a lower risk of prostate cancer as well.

That being said, if you have thyroid issues, you may want to keep soy intake in moderation, as some studies have found that isoflavones could decrease the production of thyroid hormones in the body. A study from Loma Linda University compiled the results of 14 trials and concluded that those with thyroid problems don’t need to avoid soy foods altogether, but should be sure that they are consuming enough iodine to prevent adverse effects on health.

Allergies to soy products are also very common, with one study estimating that soy allergy affects around 0.4 percent of children. Although many people do outgrow these allergies, it’s important to avoid soy products if you have an allergy to prevent adverse side effects.

Additionally, a large portion of the soy produced in the U.S. is genetically modified, with some reports estimating that up to 93 percent of crops are genetically engineered.

Genetically modified organisms (GMOs) are associated with a number of health concerns, including antibiotic resistance and a higher risk of developing food allergies. GMO crops are also linked to negative environmental effects as well, such as decreased biodiversity and toxicity to certain species, including honeybees. Selecting organic soy products is a simple way to ensure that your foods are produced from non-GMO crops.

Bottom Line

  • With all the controversial and conflicting information out there, many people are left wondering: is soy bad for you?
  • Some of the specific compounds found in soybeans have been shown to help lower cholesterol levels, improve reproductive health, decrease symptoms of menopause and reduce the risk of certain types of cancer.
  • However, because isoflavones mimic the effects of estrogen in the body, there are several potential soy side effects in females and males alike to consider as well.
  • In particular, high amounts could potentially affect levels of testosterone in men, although research has turned up conflicting results.
  • Additionally, although there are often concerns about whether soybeans may impact hormone-linked cancers like breast cancer, several studies have found that minimally processed varieties could actually protect against cancer.
  • Finally, not only are soybeans a common allergen, but they are also often genetically modified and may impact thyroid function in those with low levels of iodine.
  • Keeping your intake in moderation and selecting non-GMO, minimally processed and fermented varieties whenever possible can help minimize any adverse effects on health and maximize the potential benefits.

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