All About Soy


Soy is a long-standing “hot topic” in the nutrition and health industry, mainly because there are so many conflicting opinions and studies that fall on various ends of the spectrum. It can be super confusing when you are trying to navigate the world of soy and I know many people who avoid it altogether because they are just so confused about it!

My hope with this blog post is to break down some of the research for you and help you understand some of the most polarizing topics when it comes to soy. I did my absolute best to round up credible information and studies to answer some popular soy questions. While this certainly isn’t an exhaustive list of all health concerns and questions related to soy, my goal was to break down some of the more common questions I get about soy and to make the science and research easy to understand. My mission is to always make these nutrition and health topics easy to understand and apply to your daily life and habits! 

What is it?

Soybeans are the whole food legume native to eastern Asia. Soybeans can be eaten on their own- commonly known as edamame- but they are also dehydrated into soy nuts or used for other food products. Soy can be processed or fermented to make milk, protein powder, oil, tofu, miso, tempeh and more. 

Nutrition facts

Soy contains protein, fibre, antioxidants, phytonutrients, vitamins and minerals that help support our body and our health in various ways. Unlike many other plant-based protein sources, soybeans are a complete protein. This means they provide all of the essential amino acids that the body needs.

Soy also contains isoflavones, known as phytoestrogens, which are phytonutrients that actually resemble estrogen. I’ll touch more on this later in the post!

Keep in mind that various soy products available will all have different compositions of nutrients and potential benefits/side effects. It’s important to note that the isoflavones are often the components that are manipulated (i.e. administered in various doses) when studies are looking at the potential benefits and/or implications of soy. In these studies, isoflavones are often isolated and taken in supplemental form, rather than in food form. Concentrated, supplemental isoflavones will have a very different effect on the body compared to consuming whole, natural soy food products. 

Of course soy products contain these isoflavones naturally so I’m not saying studies that look specifically at isoflavones are useless. But it’s important to look at the bigger picture of a study when making claims about a food and its potential effects on the body. When it comes to food, we have to remember the sum is greater than its parts!

The nutrition information will also be very different depending on the form of soy you are consuming. Tofu is going to be a lot higher in protein than soy milk and soybean oil will be more heavily processed and refined compared to tempeh. It’s all relative to the form that you’re eating it in! 


Soy’s phytoestrogens are the reason that so many conflicting opinions exist around soy and women’s health, particularly for postmenopausal women. 

Phytoestrogens are estrogen agonists; this means that they can bind to our estrogen receptors in the body and activate them. These phytoestrogens take up those receptor binding spaces and produce a weak estrogenic effect (weak compared to how our own natural estrogen behaves). As a result of this, our own estrogen is then not able to bind at these receptor sites where the phytoestrogens have attached. 

It’s important to note that not all phytoestrogens will have the same effects in the body. Though it may sound ominous, phytoestrogens blocking receptor sites for our own estrogen isn’t necessarily a bad thing. Some will actually block estrogen’s effects, while others will mimic it; but its still a weaker effect compared to our own estrogen. Phytoestrogens can actually be found in other nuts, seeds, legumes, vegetables and fruit. Obviously for the purpose of today’s post, I’m just focusing on phytoestrogens in soy. But it’s important to understand that we find these phytoestrogens in a number of different foods.

As you likely know, during menopause, estrogen levels decrease. For this reason, soy has been studied to see if these phytoestrogens could potentially help reduce the side effects associated with low estrogen like hot flashes. Studies have shown that isoflavone supplementation helped reduce the frequency and severity of hot flashes; but for the most part, soy has not been shown to drastically improve other symptoms associated with menopause. 

The other “downside” of soy supplementation for addressing menopause symptoms is that it takes a long time for the effects to take place. This was studied in comparison to traditional hormone replacement therapy interventions. For example, one study found that soy isoflavone supplementation took 13 weeks to reach half of the maximum effect. Traditional hormone therapy was shown to have the same effects within three weeks. What complicates things about this finding however, is that soy actually gets processed differently depending on your gut bacteria and genetic decent. Women of Asian decent have been shown to produce more of the active form of isoflavones, called equol. Depending on your background, your conversion of isoflavones could be even less effective, rendering soy isoflavones essentially ineffective as symptom management. 

The research on menopause and soy ultimately shows that soy consumption may produce mild beneficial effects for symptom management, but it’s not likely to be an effective cure. 

Breast cancer

We know that some forms of breast cancer cells are hormone receptive. This means that “they can use estrogen found naturally in your body to grow and divide” (Canadian Cancer Society). Because of the phytoestrogens found in soy, some individuals worry that this could be a trigger for breast cancer. This is of particular concern for those individuals who have previously had breast cancer or are genetically at risk of developing breast cancer. 

However, the research shows that regular soy consumption actually decreases breast cancer risk. It has also not been shown to be harmful for breast cancer survivors. Regular soy consumption was defined as 1-2 servings per day, with a serving equaling about ½ cup of whole soybeans or tofu. A meta-analysis (a statistical procedure that combines data from multiple studies) of randomized control trials showed that soy isoflavone supplementation specifically had no effect on breast density, which is a common marker for breast cancer risk. Overall there was a reduced risk of breast cancer with both soy food and isoflavone consumption.

It’s important to note that some of the studies that looked at soy and breast cancer risk are actually observational. This means they observe a large group of women over many years, record their diet and see who (if any) develops breast cancer. Observational studies are not 100% fact however, because there are no controlled factors. Soy consumption isn’t the only intervention at play in these studies. This means that the women observed who ate soy, could also potentially be doing other things that are supporting their health. Women who eat soy products are potentially more likely to eat more plant-based, less fried food, exercise, drink water, and the list goes on. These studies cannot conclude for a fact that soy is specifically the reason they haven’t gotten breast cancer; it could have been any one of their food and lifestyle habits, or a combination of them, that has kept them cancer free. Regardless, it’s still worth noting that soy was consumed regularly during these studies, and there was a correlation to reduced breast cancer risk.

Remember what I said earlier about food being more than the sum of its parts? This could not be more true when it comes to soy and cancer! Soy is so much more than just its phytoestrogens. There are other phytochemicals that soy contains that actually provide the body with cancer-protective effects. There are also the various forms in which soy can be consumed; some research indicates that fermented soy products (like tempeh and miso) are more beneficial than non-fermented. 

As with other topics in the nutrition and health world, the research is vast and it can be confusing. There are many different factors that can be manipulated during a study and they can all have various outcomes as a result. The bottom line is that moderate soy consumption has not been shown to increase breast cancer risk.

Men’s health

Thanks to those phytoestrogens, it’s a common belief that soy will negatively impact men’s health by interfering with testosterone. I’ve actually had men tell me they avoid soy entirely because they don’t want to “get boobs”. True story. I’ve also read some not-so-credible blogs that have said that soy consumption for men isn’t recommended as it is likely to promote “feminine characteristics”. Cue the eye rolling and face-palming. 

As with many of the ridiculous nutrition claims out there, the facts around men's hormones and soy have been wildly exaggerated and taken out of context. A meta-analysis of 15 different studies showed that soy supplementation did not have any significant effect on total testosterone or free testosterone. Similar studies have been done on male athletes with soy supplementation and there were no significant results that indicated any impact on testosterone or estrogen levels. Soy was not shown to significantly impact male fertility in studies either. 

It’s important to note that soy can have negative effects on male hormones when consumed in excess. In these same studies, two reported cases of negative effects were documented. These side effects included gynecomastia, erectile dysfunction, and low libido. BUT (and that’s a big but) keep in mind, one male was consuming 2.8 litres of soy milk per day for 6-12 months, and the other male was following a vegan soy-rich diet. It’s safe to say that most people wouldn’t be drinking nearly 3 litres of soy milk every day. For the record, I would advise against anyone consuming any beverage (other than water) in those amounts on a daily basis. 

This also shows that any male who prefers to follow a plant-based diet should ensure some variety with their protein choices. Just as omnivores should aim to change up the proteins that they eat, vegans/vegetarians need to as well. The good news is there are so many fantastic plant-based protein options that aren’t soy!

The bottom line is reasonable amounts of soy products will not negatively impact hormone levels or fertility in men. 

Thyroid health

Some animal studies support the conclusion that soy has a negative impact on thyroid function due to the phytoestrogens and goitrogens it contains. Goitrogens are substances that impact iodine uptake by the thyroid, essentially limiting its functioning. However, human studies have failed to show that soy significantly impacts thyroid function in otherwise healthy adults. 

Ultimately the research shows that soy consumption may lead to thyroid function issues in individuals who are already dealing with an underactive thyroid. The main connection and implications of soy on thyroid function is in those individuals who are susceptible to thyroid issues. It’s interesting to note that many of the studies reported that the negative effects soy on susceptible individuals could be avoided by ensuring adequate iodine intake in the diet. Most studies done on healthy adults have not shown any adverse thyroid effects in connection to soy consumption. 

Genetically modified 


Soybeans are one of 5 genetically modified crops produced here in Canada (canola, corn, potatoes and sugar beets are the other four), and over 90% of soy produced in the United States is genetically modified. 

There is a lot of debate over whether genetically modified organisms (GMO’s) are safe to consume and safe for our health and our bodies long term. Genetically modified soy contains the pesticide glyphosate, which is extremely controversial and has a lot of implications for our health. Genetically modified soybeans have also been shown to be of poorer nutritional quality compared to organic soybeans.

From a holistic health viewpoint, I struggle to believe that genetically modified foods are 100% safe for our health. I don’t believe that we have enough long-term research to say without a doubt that these foods are safe and aren’t causing problems to our health. I always advocate for high-quality, natural foods and genetically modified foods are the opposite of those qualities. In an effort to provide my body with the best quality food I can, I will always look for non-GMO soy and I would encourage you to do the same.

While I won’t get into a huge discussion about GMO’s for this post, I just wanted to shine light on the fact that a lot of soy out there will be genetically modified, unless it specifically states that it is organic or non-GMO. I always recommend looking for those brands that indicate their soy is non-GMO. You can easily find the “Non GMO Project Verified” symbol on labels to ensure you’re consuming a high-quality, natural brand.

Best practices for eating it

By now you should have a pretty clear understanding of some of the benefits of soy and why we don’t need to be afraid of it. So how should you be consuming soy? It’s really a personal preference but there are a few things to keep in mind when choosing your soy based foods.

  • Look for non genetically modified soy- for reasons mentioned above

  • Avoid soybean oil- soybean oil is one of the most heavily processed versions of soy and it’s best to avoid it. It’s not a healthy fat and it promotes inflammation in the body. You’ll find soybean oil in processed, packaged and fast foods. It will always be listed as an ingredient on the food label.

  • Avoid processed soy- processed soy include textured vegetable protein, soy burgers, soy protein powder, veggie dogs etc. These highly processed food products contain various versions of soy. The processing isolates the protein in soy and strips of a lot of the other benefits that soy naturally has (like the vitamins, minerals and antioxidants). It’s always best to aim for whole food versions of soy like edamame, tofu and tempeh. 

  • Fermented is best- fermented soy foods like miso and tempeh come with the additional benefits of fermentation. These products are easier to digest, contain higher amounts of nutrients and have helpful bacteria that will benefit your gut microbiome. For this reason, it’s beneficial to include fermented soy in your diet on a regular basis.

  • Switch it up- it’s always a good idea to get some variety in your diet! Instead of always eating tofu, try tempeh or have some edamame for a snack. Variety in your diet keeps things interesting meaning you’ll never get bored; it’s also important to have variety so you’re getting the most variation in the nutrients you’re fueling your body with.

  • Moderation- as I mentioned above, it’s not ideal to consume huge amounts of soy for long periods of time. But it’s also not ideal to consume large amounts of any food for long periods of time. Too much of a good thing can still be too much. The general recommendation for “moderate consumption” is 1-2 servings per day.

Final thoughts

My opinion with most things food and nutrition is always centered on moderation. We create a lot of issues for our food habits and our relationship with food when we have the mentality that certain foods are the sole causative factor specific health concerns. My ultimate stance is that small, regular amounts of good quality soy products can be beneficial for our health.  

It’s really important to remember with any nutrition or health topic that there at a lot of studies out there. There are a lot of studies with a lot of different outcomes. Just because one study found that consuming x = y doesn’t mean that x will actually equal y. By that I mean that there are a lot of different ways that studies can be conducted, and it doesn’t always mean that their findings will be significant or that their conclusions will actually ring true in real life. We see this a lot in the health and nutrition world, headlines will scream that a certain food causes cancer, or another food is linked to heart disease, but it isn’t always the whole picture. My point is, one study’s findings aren’t the be all, end all of the recommendations around a certain food. 

I’m going to repeat myself for this last point because it is so important- food is so much more than its individual components. Isolating one part of a food and controlling it in a study setting is not always going to represent what will happen when you consume the whole food in moderation. Studies are designed this way because its important to help us understand what components could potentially be beneficial or have its risks. This can be extremely helpful and beneficial for us as it can help us identify how we can use food and nutrients to treat and prevent disease. 

When it comes to understanding this research and relating it to your life, we just need to remember that food in its whole forms has so many benefits for so many different reasons. Soy is so much more than its phytoestrogens and our body responds to soy as a whole, not just its estrogen mimicking properties. Consuming high quality soy, in its whole or fermented form, has a lot of benefits to your health and your body. Ultimately there is no need to have fear around enjoying a bowl of edamame, if that’s your thing!

Alaina Yvon-Moreau