For the longest time, I thought soy protein was a good thing.

I did not know much about it, but generally heard it talked about in a positive way. I was first introduced to it by my vegetarian friends, but after a while, I started seeing it used everywhere, from soy milk to soy-based protein supplements. However, I began to wonder, “If soy is so cheap, meat-less, full of protein, why is the whole world not using these little beans?”

Well, it turns out soy is not as healthy as people may think (myself included) and it’s especially not healthy for men.

Soy actually has many negative side effects. It is full of genetically modified organisms (GMOs) and has a high level of phytoestrogens, which as you’ll see below, may be harmful to men.

So to help shine some light on these dangers, here are the top five reasons to avoid soy.

1) It increases your estrogen levels 

If you’re trying to get some gains in the gym and you’re pounding back soy protein, you may start seeing your body grow…just not in the right places. Men’s Health ran a story a few years ago about a man whose breasts began to become swollen and painful after drinking soy milk on a daily basis. The man, who was a retired US army officer, said it felt like his body was feminizing.

The reason for this is that soy contains phytoestrogens, a compound that mimics the body’s natural estrogen hormones. These high levels of estrogen can promote aesthetic issues (such as man boobs) or even worse health problems such as thyroid dysfunction. Soy can make you have more estrogen and less testosterone than you would normally have when taking other types of protein.

2) It can cause infertility   

A Harvard University study found a higher intake of soy and isoflavones is associated with lower sperm concentration in men. While the reduction was small, it was considered statistically significant.

The phytoestrogens that mimic your body’s estrogen hormones are the reason soy can also lead to infertility in men. Guys who consume high doses of soy may not only see a reduced number of sperm, but lower quality too. This lower sperm quality is caused by a lack of androgens in your body that are reduced when you have significant levels of estrogen.

3) Takes away from other important minerals and vitamins 

Soy has high levels of phytic acid and these inhibit your body’s ability to absorb important minerals. When you consume soy foods and supplements, you are actually increasing your body’s needs for vitamins and minerals such as Vitamin D, Vitamin B-12, zinc, calcium, copper, iron and magnesium (something that many people are already deficient in).

4) Results in a smaller penis 

A smaller penis? That can’t be right! Well, while it doesn’t cause  your penis to decrease in size, soy can cause a boy’s penis to grow at a reduced size and will result in a smaller penis. This can occur if a mother is consuming high levels of soy protein while pregnant or if a developing child consumes a lot of soy in their early years of development.


5) It negatively affects your behavior

While not as drastic as the other side effects, soy can cause you to show a more aggressive behaviour.

Soy can negatively affect your behavior, according to a study published by researchers from Wake Forest University Baptist Medical Center who divided adult male monkeys into three groups for a 15-month study. Each group of monkeys was given different levels of soy protein, with one group given only protein from milk and other animal sources. They found that the monkeys who were fed the high amount of soy demonstrated more aggressive yet submissive behavior than the other monkeys. These more aggressive monkeys also spent less time with other monkeys and increased their alone time.