Does Soy Contain Estrogen?

Some consumers avoid soy products due to concerns about them containing estrogen, a female sex hormone. Contrary to popular belief, soy doesn’t contain human estrogen. Instead, soy contains soybean isoflavones, or phytoestrogens, which resemble human estrogen but don’t interact with our bodies in the same way. Learn more about estrogen vs. soy phytoestrogen and how they can be a healthy part of your diet.

Estrogen vs. Phytoestrogen (Isoflavones)

Hormones are chemical messengers that travel through your bloodstream to give instructions to your tissues and organs. Estrogen, the female sex hormone, is mainly produced in the ovaries to help regulate the reproductive system and menstrual cycle. It helps develop breast tissue during puberty and naturally decreases during menopause. Despite being known as the female sex hormone, estrogen is also produced in the male adrenal glands and testes.

Phytoestrogens, or isoflavones, are compounds that occur naturally in plants, especially beans. Soy foods are a source of phytoestrogen, and phytoestrogen in soy has two major roles: warding off disease and converting nitrogen from the soil into essential compounds in the roots.

Due to their chemical structure, phytoestrogens resemble human estrogen. They’re referred to as plant estrogens because their effect on plants is similar to estrogen’s effect on the human body. Since phytoestrogens look like human estrogen, some consumers avoid phytoestrogen-rich foods, such as soy foods, out of a fear of consuming human estrogen. However, phytoestrogens are very different from regular estrogen and don’t function like human estrogen when eaten.

How Phytoestrogen Interacts with Estrogen Receptors

Estrogen receptors are proteins that live inside your cells and are activated by the hormone estrogen. The two receptors are named estrogen receptor alpha and estrogen receptor beta. Estrogen binds to these receptors to help your cells carry out important functions. While human estrogen uses both receptors, phytoestrogens, like the ones found in soy, favor the beta receptor. Compounds that activate this receptor can potentially help prevent cancer.

Does Soy Feminize Men?

Unlike regular estrogen, research indicates that soy phytoestrogens don’t have any effect on sperm motility, sperm density or semen. Phytoestrogens also don’t increase estrogen levels in men or lower their testosterone levels. When combined with strength training, soy protein can be just as effective as animal protein for increasing muscle mass.

Does Soy Affect Breast Tissue?

Regular estrogen has been linked to an increase in breast tissue, which can increase your risk of developing breast cancer. Phytoestrogens, unlike human estrogen, don’t cause breast cells to increase and have a neutral effect on breast cancer risk. Some studies show that soy isoflavones may even help protect against breast cancer.

Now that we’ve debunked a common myth about soy, why not incorporate this isoflavone-rich food into your meals with one of our soy recipes? You can also visit our Soy Myths and Facts page to learn more about soy and its effect on different demographics. Curious about soy production and farming? Visit our soy farming hub to learn how soy is produced sustainably by U.S. soybean farmers.