When faced with a cold glass of soy milk or a delicious piece of smoked tofu, men are more likely than women to reject these soy products, a high quality, plant-based protein alternative [1].
From edamame, tofu, tempeh, miso and natto to basics like soy milk, soy products are affordable, everyday foods found in a variety of different dishes and diets. Nearly all soy products are protein-rich, high in iron and provide a generous amount of isoflavones — a phytoestrogen known to reduce the risk of heart disease and decrease cholesterol levels [2].
Despite the abundance of nutritional benefits in soy foods, there is an undeniable stigma around soy — especially for men. The mainstream adoption of soy may have male consumers skeptical, but soy products have been consumed by humans for thousands of years without adverse effects [3].
So what’s the reason for the skepticism and stigma? Unfortunately, science misinformation has painted a poor picture of soy nutrition for men. In this article, we will debunk the top three myths about men and soy consumption.
Myth #1: Soy results in “feminization” of men (a.k.a growing breasts)
This popular myth comes from the idea that soy products are high in estrogen, therefore mimicking the effects of human estrogen in the body. But — not one single human study has been able to find a cause and effect relationship between soy and breast growth in men.
The only scientifically documented case of soy causing breast growth comes from an unusual case study, where a man grew breasts after consuming nearly 3 litres of soy milk per day [4].
It’s important to understand that the estrogen found in soy products are isoflavones, a plant estrogen. While these plant estrogens have a similar structure to human estrogen, they cannot cause the same effects as human estrogen when eaten in normal amounts. In normal amounts, isoflavones actually provide men with health benefits, such as reduced risk of heart disease [5].
Consuming any food or drink ( including water) in large amounts can render it dangerous. Therefore, consuming regular portions of soy products is perfectly healthy for men to enjoy.
Myth #2: Soy can decrease testosterone levels in men
Some people believe that the plant estrogen in soy products could reduce levels of testosterone in men. But, a recent 2021 study that analyzed clinical data over the past twenty years concluded that soy products do not affect testosterone levels in men [6].
In fact, early evidence suggests that soy consumption could decrease the risk of prostate cancer in men [7]. As testosterone levels are usually lower in men with or at risk of prostate cancer [8], soy products might even help reduce the cell replication, but more evidence is needed [7].
Myth #3: Soy protein is not optimal for muscle building in men
Like animal protein, soy is a complete plant-based protein that includes the nine essential amino acids needed for muscle repair and growth. A recent study found that there was no difference between soy and animal proteins when it comes to muscle building [9].
Leucine is the most important amino acid to jumpstart the muscle repair and growth process. The International Society of Sports Nutrition recommends that 3 g of leucine are consumed after exercise for muscle building [9].
Some plant-based proteins are criticised for their low leucine content, but you can easily reach your leucine needs by mixing and matching different soy products. For example, a post-workout meal containing 1 cup of tempeh and around ¾ cup of lentils provides nearly 4 grams of leucine per serving [10] . Similarly, a post-workout shake of 1 ½ cups soy milk, 1 scoop soy protein powder and 2 tablespoon of peanut butter provides around 3 grams of leucine [11].
Men could be missing out on the health and nutritional benefits of soy
Avoiding soy products due to myths and stigma could result in men missing out on important health and nutrition benefits.
Besides being a high quality plant-based protein, soy products like tofu, tempeh, natto, edamame and soy milk are high in isoflavones. Isoflavones can decrease the risk of heart disease, promote muscle building and may even decrease cancer risk.
Beyond human health, increasing our demand for soy products could decrease the demand of soy products for animal feed, where soy meal is commonly fed to animals. Animal livestock is estimated to account for 14% of total global greenhouse gas emissions [12]. Ultimately, the benefits of soy products extend beyond human health and also impact our planetary health, which impacts both men and women alike.