Soy - is it good or bad for you?

One of the most common questions we are asked is "But isn't soy bad for you?". At FULLsome we don't believe in trying to convince people to eat soy - that's not our jam. We want people to feel 100% happy with what they are putting in their bodies -that's our whole philosophy. So the decision to buy and consume soy at the end of the day is your decision. Right on. That said, we have done a boat-load of reading and researching on soy and it's impact on the health of humans.

Plant-based eating is on the up-and-up, in South Africa but also all around the world. Many people are becoming aware of the benefits (health, environmental and animal rights) of a plant-based diet through social media or are facing health issues where doctors are telling them they need to make changes in order to improve their wellness. Inevitably, one of the main changes will be to their diets. Typically, the advice is to avoid highly refined carbohydrate foods like white flour, to cut down on meat, dairy, saturated fats and sugar, and to try and eat more veggies.


This is totally sensible advice, and it sounds simple. But when a person who is not well-versed in plant-based eating sits down to actually apply this advice – they can wind up quite stumped as to what to eat. There is feeling that they need to replace the meat portion of their meals with a meat alternative. A quick Google search later and the main options that come up are meat look-a-likes made from either soy, pea protein or seitan (which is pure wheat gluten) – or things that sound a little bit more exotic like tofu and tempeh, which are both made from soy beans. 


This is when alarm-bells go off. “Wait! Hold the phone! Doesn’t soy cause cancer? Someone told me that once!” and quite quickly the person is left feeling confused and worried. Well, here is the thing – soy is not only safe, but actually healthful. Unless of course you have a soy allergy – then not so much. However, only 1 in 2000 people are allergic to soy, which is about 40% less people than are allergic to dairy, and 10% less than are allergic to the other common allergens like nuts, shellfish etc. (Greger, 2016). 



So where does the confusion over its association to cancer come in, and in specific hormone related cancers? This may sound like the start to a corny joke but it all began with an Australian farmer who, back in the 1940s, noticed fertility issues with his sheep that were eating a lot of clover. Clover is rich in plant-derived chemicals called phytoestrogens…as is soy. Many other foods such as plums, pears, apples, grapes, berries, beans, sprouts, cabbage, spinach, grains, hops, garlic and onion (Bacciottini, et al., 2007) contain phytoestrogens, but not in the same concentrations as soy. Phytoestrogens have a similar shape to the human hormone of estrogen, and the worry (80 years ago) was that consumption of soy may lead to adverse health effects if eaten regularly or in large quantities (Davis C. , 2019). 


Fast-forward to today – and we’re a long way down the road with testing and understanding soy and how it interacts with the human body. In soy, there are four main classes of phytoestrogens, and the class most studied is that of isoflavones. Isoflavones can be received by estrogen receptors in different types of cells in our bodies, the same way that human estrogen can be received. It has taken a long time to learn the details since the 1940s, but human cells have two types of estrogen receptors – Alpha and Beta receptors. Plant based phytoestrogens preferentially bind to the Beta receptor and in areas of the body that don’t have Beta receptors, isoflavones have minimal impact (Greger, 2016). This is a good thing – because they do really important work in those cells that human estrogen may bypass. They can bind to Alpha receptors, but then they are competing with your body’s natural estrogen and you’d have to consume significantly wild amounts of soy to have enough isoflavones in your body to have a proper punch up with your natural estrogen. I’m talking eating buckets of the stuff every day. 


To get an idea of how isoflavones are viewed in 2021 and to understand the important work they do for you - leading gastroenterologist Dr Will Bulsiewicz states in his 2020 best-seller book Fiber Fueled “isoflavones have a number of health benefits, including: lowering cholesterol, strengthening bones, treating menopausal symptoms, lowering risk of coronary heart disease, and reducing risk of prostate/colon/breast/ovarian cancers” (Bulsiewicz, 2020). 



The next thing people typically worry about with eating soy is its GMO verse non-GMO status. While research on soy and the effects of phytoestrogens has come a long way for specialist doctors to be able to safely give the green light on soy, so has commercial agriculture and intensive farming practices galloped ahead in progress since the 1940s. And this progress has come in the form of genetically modified crops, which requires chemical based farming practices. Super short and sweet – GMO soy has been modified genetically to be able to accept glyphosates – which are found in herbicides like Round Up. The weeds will die, but the plant won’t. Now there are standards in agricultural practices for what is an acceptable level of glyphosate in crop spraying, and this standard is 20 parts per million. This equates to a safe ingestion level of glyphosates at 0,5mg per kg in bodyweight. If you weigh 60kgs, that is 30mg per day. This would be a buffered amount too, so according to regulatory bodies – you would be able to ingest 30mg safely (Davis C. P., 2019).


One of the best articles that sums up the conversations around soy is by Dr. Chana Davis of Fuelled By Science - and you can read it here

Other articles around the safety and healthful nature of soy that are (in our opinion) balanced can be found here:



To think about the above in a balanced way, don’t forget that it is not just soy that is exposed to glyphosates, wheat and corn are the two other largest crops in the world – and they are mainly GMO crops too. Consider that a regular loaf of bread on the shelf at any grocery store is most likely made from wheat that is a GMO product. Nowadays, in South Africa and internationally, non-GMO soy is certainly making a comeback as farmers get their hands on heritage seeds. It’s not difficult at all to choose non-GMO soy-based products if the glyphosate issue concerns you – and if it does concern you this is a good thing as we should be paying attention to what is going into our body day in and day out. One very good reason (from a food snob point of view) to seek out non-GMO soy products is for taste! The majority of soy in the world is modified and grown to feed cattle – it’s subtleties and magical nuances and careful selective breeding by subsistence farmers to create the tastiest, creamiest, richest soy beans has been lost through commercial agriculture. So, regardless of potential health impacts of glyphosates, being a snobby soy afficionado will make your eating experiences that much better! 


The last main key concern with soy is that by virtue of it being a legume – it contains phytates and lectins which can act as ‘anti-nutrients’ or to put it very simply, they can interfere with your guts ability to digest and absorb micronutrients. But, and this is a big but, one of the other main foods that contains lectins is wheat. So before writing off soy beans, red kidney beans and other foods that contain lectins, remember that your burger buns, wraps, bread, pasta, doughnuts, pizzas and-and-and…all are made from wheat. Here is the thing – if you go and eat undercooked beans or wheat, then yes, lectins can be a problem. By cooking beans at 100°C for 10 minutes, 99.9% of the lectin content is deactivated. Additionally, fermenting soy deactivates 95% of the lectin content and sprouting deactivates 54% of the lectin content. What about wheat products you ask? Well, almost every single wheat product bought from a store will have gone through high temperature cooking to make it into what it is, so the lectin is totally deactivated (Rowles, 2019). Unless you’re eating beans and wheat raw (good luck with that), micronutrient absorption should not be a major concern for you. 



If you’re keen to eat soy – it’s always recommended to go with soy based foods that are not too highly refined. Tempeh, miso, tofu, soy milk, tamari sauce, edamame beans are all ideal sources of soy protein as they are either fermented or cooked at high temperatures and are closest to their wholefood form (Bulsiewicz, 2020). Tofu and tempeh are great sources of complete proteins too, with 150g of firm tofu delivering 12g protein (Dietetics Association of South Africa, 2019). That said – a few commercial soy burgers, sausages and faux meats here and there are not going to harm you. What about isoflavones? According to Dr Chana Davis of Fuelled By Science, it is commonly accepted that 3 to 4 servings of soy-based food per day is safe to eat, which would deliver around 100mg of isoflavones into the body. Depending on what type of soy based food you’re eating, 3 to 4 servings can deliver up to 48g of protein – which is 90% of the way to a recommended daily protein intake for an adult (Dietetics Association of South Africa, 2019). 



And there we have it – if you take the time to do a little reading – soy is safe, soy is beneficial and soy is pretty darn cool. Like anything – if you are eating one type of food all day every day, you are going to suffer because our guts need a wide variety of foods to get the full spectrum of macronutrients, micronutrients and fibre that we require to run at an optimum level. Soy foods should be viewed as ubiquitously as chicken or beef in our modern diets – so the next time you’re staring at the packages of tofu in the vegan section wondering how on earth you cook and eat it – grab one! Within 60 seconds of Googling tofu recipes you will be amazed at how easy it is to transform it into a protein rich meal, and your gut will thank you for it.