If you’ve been in the world of physical fitness, lifting, or bodybuilding, you know that, along with your workout regimen, proper nutrition including protein is critical. Especially as we age, our ability to maintain muscle mass declines without proper fuel and exercise, so it’s important to pay attention to protein intake. If you’re looking to actually build muscle (rather than just maintaining), then consuming enough protein is even more important for you.
Historically, whey protein has been the go-to source of easy-to-digest proteins for men who are looking to fuel up, due to its bioavailability and the fact that it’s sourced from dairy (ie, an animal protein). The conventional wisdom has been that animal proteins are the most efficient fuel sources for men looking to bulk up. And the flip side of that has been that plant-based proteins are perceived to be inferior for the opposite reasons (less bioavailable and sourced from plants). Soy protein, in particular, has been demonized due to its “estrogen-mimicking” compounds, and due to lots of bad science that was spread by bad journalism, many health experts have advised against boys and men consuming it at all.
But in fact, these beliefs aren’t supported by the latest scientific findings, specifically when it comes to soy protein. Let’s dive into the scientific research that addresses the effects of soy on men and answers the question, “Is soy protein bad for men?”
Soy Isoflavones: The Soy Estrogen Myth
For some quick background on why some ‘experts’ believe that soy is bad for men, you need to first understand soy isoflavones. A type of phytoestrogen, isoflavones are plant-derived chemicals (phytochemicals) present in all kinds of legumes but most potent in soybeans. The level to which the soybeans are processed will determine the potency of isoflavones in the soy product you’re eating. For example, foods that are minimally processed like the whole bean (edamame) and tofu have greater isoflavone content than a more processed protein powder.
Health Benefits of Isoflavones
Overall, isoflavones are actually very beneficial for human health. They’re a type of antioxidant that’s been linked to all sorts of potential benefits. Antioxidants are called as such because of their ability to prevent cell oxidation in the body and reduce the occurrence of free radicals. Free radicals create oxidative stress that can lead to cell damage. Cell damage is the beginning point for disease, including cancer of most types, inflammation, and cardiovascular disease.
A number of studies have demonstrated that including isoflavone-rich soy foods in a healthy diet could offer protection and support for a number of systems in the body. For example, isoflavone-rich soy may:
- Improve cholesterol levels by raising HDL (good) and lowering LDL (bad)
- Lower the risk of heart disease and stroke by reducing inflammation and improving elasticity in blood vessels.
- Help maintain healthy blood sugar by lowering insulin resistance, a precursor to type 2 diabetes.
- Provide protection against prostate cancer and cancer of the digestive tract, in addition to reducing mortality among digestive tract cancer patients (both men and women).
After taking in this list of the various health benefits of soy, it’s hard to imagine that soy could have some negative health effects as well. While no one food is the perfect food for every human being on earth, soy gets a bad rap for a number of unfounded reasons. Let’s unpack the fears around the effects of soy on men.
Does Soy Increase Estrogen in Males?
As we double click into all the myths surrounding isoflavones and “phytoestrogens” conversations around increases in estrogen always arise and include questions around sperm count, change in appearance, and others; but let’s dig into the facts.
The truth is that none of these claims are born out in the research. The small studies that seemed to show that sperm count was reduced in men consuming soy were subsequently debunked by a number of follow-up studies done on a larger scale. The handful of studies showing any sort of negative effects of consuming soy have all been done using extremely high amounts of soy (over four servings daily), beyond what most people would likely consume.
In fact, a recently published analysis looking at 41 clinical trials and testing almost 2,000 men debunked the soy estrogen myth once and for all. This study found that, across all trials analyzed, soy protein had zero impact on testosterone or estrogen levels in men. Jim White, RDN, American College of Sports Medicine Exercise Physiologist, and owner of Jim White Fitness & Nutrition Studios commented on this study, “Time and time again, research has shown that soy protein is a great choice for your health and won’t negatively impact your hormone levels. With so much misinformation circulating, it is imperative that we look to credible sources such as these studies.”
Importantly, popular magazines like Men’s Health, which have been vocally anti-soy in the past, have changed course due to substantial (and mounting) research debunking the idea that soy increases estrogen in males or has any negative impact on male hormones. In fact, back in 2018, they released an article touting the benefits of soy protein for men as an excellent dairy-free alternative and even ranked it higher than almond milk, coconut milk, and rice milk.
Soy Protein Holds Up
Now that we know that the effects of soy on men’s health and fertility aren’t what most scientists believe them to be, let’s talk about how soy protein holds up against animal sources of protein like whey.
As a rule, when looking to bulk up, both men and women should aim to ingest about double the protein of sedentary people — about 0.7 grams per pound. A recent study showed that when 16 grams of protein daily were added to the diets of older men and women, participants were able to maintain or even increase muscle mass, strength and performance. Whey and soy protein resulted in identical gains, and these gains were seen even in sedentary participants.
An analysis like this should be a great source of comfort for vegan men (and women) who are looking for a protein source to support their fitness efforts without involving animals. In fact, a 12-week study comparing physically active vegans consuming soy protein with active omnivores consuming whey resulted in comparable muscle gain and strength improvements.
Beyond the isoflavones and high-quality proteins, soy is also an excellent source of other beneficial nutrients, including fiber. It contains both soluble and insoluble fiber, both of which offer their own digestive health benefits. Soluble fibers, specifically, are digested by bacteria in your colon, which creates short-chain fatty acids, which may offer protection against colon cancer.
Soy also contains a number of vitamins and minerals, including molybdenum, vitamin K1, folate, copper, manganese, phosphorus, and thiamine. Each of these vitamins and minerals offers its own health benefits and should be part of any balanced diet.
Effects of Soy Men Can Count On
It’s so important to understand the science behind health claims you may read in a popular magazine or online from your favorite health guru. While well-meaning, it’s easy to read a single study and then draw an incorrect conclusion, due to a lack of context. Well-intentioned misinformation about the hormonal effects of soy on men has persisted in popular magazines and health blogs for years, but the science doesn’t support the claims.
In truth, soy is an excellent source of protein for men (and women), offering a wide array of benefits beyond just a high-quality protein source. There are a number of nutritional advantages to adding soy back into your diet, including a wide array of vitamins, minerals, and other beneficial phytonutrients. Not only is soy an excellent source of protein and fiber, it also stands up against whey protein in clinical trials when it comes to building and maintaining muscle mass.
Most importantly, the myth around phytoestrogens in soy is simply not supported by current scientific findings. There is no evidence to suggest that isoflavones in soy inhibit testosterone or increase estrogen in men, nor is there evidence that soy reduces sperm count or semen parameters in men.
Rest easy knowing that you can add soy back into your healthy diet as a reliable source of plant-based protein for men.