How Bad Is Soy for You?

Medically Reviewed on 9/15/2021

The myth about soy

Soy products like tofu, tempeh, soy milk, miso, and edamame come from soybeans. Soy is not bad for you and may in fact help guard against breast cancer and inflammation and boost kidney function, heart health and bone health.
Soy products like tofu, tempeh, soy milk, miso, and edamame come from soybeans. Soy is not bad for you and may in fact help guard against breast cancer and inflammation and boost kidney function, heart health and bone health.

Soy products like tofu, tempeh, soy milk, miso, and edamame come from soybeans. They are rich in nutrients like fiber, protein, magnesium, iron, potassium, and zinc. But, is soy bad for you at all?

Soybeans are legumes that contain isoflavones, a class of phytoestrogens that mimic the estrogen your body naturally produces. Phytoestrogens gave soybeans a reputation for being potentially harmful to your health. It is a myth that phytoestrogens have the same effects on your body as traditional estrogen. Instead, isoflavones in soy may benefit your body by:

The molecules of isoflavones found in soy are so small that they act like anti-estrogens. Instead of increasing your estrogen levels, isoflavones offer balance to natural estrogen levels that are too high.

Soy nutrition

In addition to isoflavone, soy also offers high-quality nutrients your body needs. Soy protein has all nine of the essential amino acids that your body cannot make on its own. Other proteins may have several amino acids, but not all of them. Soy is a complete protein because it has all nine of these amino acids. Protein helps your body build and maintain strong bones, muscles, and other tissue.

Soy products also come fermented or not fermented. Non-fermented soy products offer traditional nutrition. Fermented soy products have the addition of cultured good bacteria, yeast, and mold. The fermentation process makes soy easier for your body to digest and absorb nutrients, offering digestive benefits.

Potential health benefits of soy

Breast cancer. Consuming soy may reduce your chances of developing breast cancer. This is contrary to the myth that foods containing phytoestrogens actually increase your cancer risks.

Some studies have shown that women with breast cancer lived longer if they consumed soy products. There was also a correlation between higher soy consumption and a reduced risk of breast cancer recurring in the future.

Kidney function. Research suggests that drinking soy milk may improve your kidney function. Your body digests plant-based foods easier than animal-based foods. Soy milk may be easier on your kidneys than cow’s milk. Keep in mind that you still want to read labels and ensure your soy milk doesn’t have too much added sugar.

Inflammation. One study showed a pattern of less inflammation in women who consumed more soy products. Decreasing your inflammation also decreases your risk for cancer, heart disease, and type-2 diabetes.

Heart health. Soy products may help lower your cholesterol levels. There is good and bad cholesterol. Too much bad cholesterol clogs your arteries and increases your risk for heart diseases like a heart attack or stroke. Soy contains no cholesterol and very little saturated fat, making it a great addition to your heart-healthy diet.

Bone health. Studies show that soy may aid in making your bones stronger. One study that was published in the American Journal of Epidemiology showed that women eating a quarter-cup of tofu or more per day had a 30% less risk of developing a fracture. Another study showed that consuming soy products led to a 37% less risk of bone fracture.

Potential health risks of soy

Processed soy and cancer. Not all soy is created equally. Soy offers the most benefits in its purest form – the soybean. Foods like edamame, tofu, and soy milk offer the most health benefits. Seeing soy as an ingredient on a label does not mean the food is healthy or that it offers the benefits of soybeans.

For example, soy proteins are often isolated from soybeans to make protein shake powder. This process changes the soy so that it is more likely to increase the insulin factor in your blood. Soy protein isolate may increase your risk for developing cancer.

Allergies. Some people are allergic to soy. Signs of a soy allergy include:

Get emergency help for any trouble breathing. If you experience any of these symptoms, remove soy from your diet and talk to your doctor about your concerns. You may grow out of your soy allergy over time, so try reintroducing it to your diet after several months or years have passed.

Thyroid medication. It is possible that soy can interfere with hormone-based thyroid medicines used to treat hypothyroidism. One study showed that people who consume more soy are at a greater risk for hypothyroidism. However, the same study also showed a decreased risk for insulin resistance, inflammation, and high blood pressure.

There are risks and benefits to including soy in your diet. Talk to your doctor about your risk factors and any medications you are on to see how much soy makes sense for you.


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Medically Reviewed on 9/15/2021

Harvard Health Publishing: "By the way, doctor: Children and soy milk."

Harvard T.H. Chan: "Straight Talk About Soy."

Nutrition Facts: "Soy," "Soy Milk."

Physicians Committee for Responsible Medicine: "Soy and Health."