‘Soy Boy’: Does Eating Soy Really Lower Men’s Testosterone Levels?

For years, online communities have invented their own slang to talk about masculinity.

One of the stranger words is soy boy. To some, it might sound silly or confusing. But the idea behind it is that men who eat soy become weak, soft, or feminine. The insult has spread across forums, memes, and even everyday conversation.

But where does soy come into this? And can food really change how masculine or feminine someone looks? To answer that, we need to look at hormones.

Puberty in Men

Testosterone is often called the male sex hormone. It helps boys develop male sex organs before birth, writes Videnskab. In puberty, it deepens the voice and grows facial hair. In adulthood, it supports fertility, sex drive, muscle mass, bone strength, and even mood.

Estrogen is usually called the female hormone. It helps regulate menstruation and shapes puberty in girls. But men also need estrogen. It plays a role in sperm production, erections, and sex drive.

Hormone Balance

When hormones fall out of balance, problems can appear. High estrogen in men can cause breast tissue growth. Low estrogen can reduce sex drive and weaken bones.

Hormone balance can also be disturbed by chemicals in the environment. These are called endocrine disruptors. They are found in plastics, pesticides, cosmetics, and packaging. Even small doses can have lasting effects.

Feminizing Soy?

Soy contains natural compounds called isoflavones. These are phytoestrogens, meaning they look a little like human estrogen. In animals, they can act like weak estrogens.

They can also block estrogen from working in some cases. This has led to the belief that eating soy might “feminize” men.

But human studies do not support that fear. Research on men from China, Japan, and the U.S. shows little or no effect of soy on testosterone, sperm quality, or fertility.

The Benefits?

Some studies even suggest mild benefits. The effect of soy is far weaker than human estrogen, often tens of thousands of times weaker.

So should men worry? Not really. Eating soy in normal amounts is unlikely to cause harm or change masculinity.

Like with most foods, moderation is best. The claim that soy turns men into “soy boys” is more internet myth than science.