#153: Soy - The Benefits & The Myths
I get questions from women on my programs all the time such as:
‘Isn’t soy bad for your hormones?
‘Isn’t soy bad for your thyroid?
So, I want to clear the confusion about soy right here and also delve into the health benefits so that you can make your own informed choices as you continue to embark on your healthy eating journey!
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In today's episode, I'm going to be talking to you all about soy because it has been brought up a few times lately in both of the Facebook Groups of my programs and women often ask - doesn't soy affect your thyroid? If you've got a thyroid condition, isn't soy bad for you? Is soy bad for your hormones?
I'm going to be answering these questions and also just giving you some background information on soy. So I'm going to be going through what soy is, the health benefits and the potential downsides to soy, which are just potentials.
Most things are myths and that's what I'm here for. I'm here to really break down the science in a very easy way for you. I don't like getting too specific in these podcasts (in terms of very science chit-chat) but I do want you to know that I do have a Bachelor of Science Nutrition Degree.
I am always keeping up with the research. I've been working with women for 8 years now with my business and learning so much through them as well. I do have a lot of experience and I do understand there is so much information out there, so it's not your fault if you feel confused about certain ingredients, but that's what I'm here to help you with, through the podcast and through my programs too. I really break it down for you and give you ideas on what to eat.
Obviously, this is just my advice with my research, so still take it with a grain of salt, do your own research if you like, but I do like to simplify things for you so that you're not concerned when you hear false messages out there, whether it's in the media or people that aren’t qualified on Instagram talking, because there is so much out there and whilst there's so much good information out there to help you, it upsets me sometimes because there's almost too much where people can get confused and miss the whole point of health altogether …
So what I mean by that is that people are ignoring the fact that sugar is bad for you, trans fats are bad for you, processed foods aren't great for you and they're trying to eat healthy, but then they’re zooming into things like soy and tofu and foods that are actually good for you and missing the point altogether, whereas it's far better to zoom out and go - how can I make my diet healthy by eliminating the things that are definitely proven by science, like sugar?
Eating too much sugar has been studied intensely and it's very much proven that it is one of the leading causes of obesity, heart disease and so many other diseases in the world, whereas you come to things like soy and there's just a couple of random studies that really don't have much strength that maybe one media article will share, or one person on Instagram will share, that lack scientific backing.
Then people will zoom in on that and forget the bigger picture. I wanted to say that as an intro, but I am going to be just focusing on soy in this one and if you enjoy this, I will do some more myth-busting podcasts for you surrounding topics like this so that I can really clear your confusion, because that is always my aim because the less confused you feel and the more simple things feel, the more likely you are to keep moving forward on your health journey.
So, let's get into it …what is soy? Soy is a really good source of protein, fiber and has an array of important vitamins and minerals. It also contains health-promoting compounds like isoflavones. Though you may have heard concerns about soy's GMO status or phytoestrogen content, most scientific evidence suggests that there's no need to avoid soy products.
In fact, eating soy protein, especially whole and minimally processed foods like edamame, tofu, and tempeh may offer numerous benefits for heart health, blood sugar control, weight loss and even cancer risk and recurrence.
So, what is soy protein? Soy protein is the primary protein that's found in soy products such as tofu, tempeh, soy milk and other soy-based dairy and meat alternatives. It can also be found in the form of soy protein powder, which you can use to supplement a workout routine or add more protein to your diet in general.
Now you've got a few different types of soy foods -
You've got minimally processed soy, which is the one that I absolutely recommend the most like tofu, tempeh, natto (which is a Japanese sticky breakfast dish made by fermenting soybeans) and miso. So I am sure you are all familiar with miso soup - it's a flavourful paste that's used in soups and other recipes and it's made from fermented soybeans and barley or rice malt.
Then you've got the more processed soy, so soy milk is in this category. You can get ones that are better for you than others. I would always recommend choosing a soy milk that's made with non-GMO soybeans with not many additives at all and no added sugar and having that is totally fine.
I'm getting ahead of myself with what I'm going to recommend, but soy milk is one of the more processed ones and then on the highly processed end is soy protein powder or soy protein isolate and that's often used in things like protein bars or vegan patties like fake meat and things like that. That's more of the highly processed soy.
Now let's get into the nutrition facts and health benefits of soy foods. So, overall like I said at the beginning, soy is a good source of protein and fiber, as well as vitamins and minerals like calcium, iron, magnesium and zinc. It also contains a little bit of unsaturated fat and is free of cholesterol.
It has about 180 calories for firm set tofu, which is about half a cup.
So the health benefits of soy - it has been found in many scientific studies (and when I say scientific studies, I'm talking about the gold standard in scientific studies, so peer-reviewed, double blinded studies) that soy may protect heart health.
Soy foods appear to have positive effects on heart health. In one review of 35 studies, soy intake lowered LDL (which is your bad cholesterol) and raised HDL ( which is your good cholesterol). This matters obviously because high levels of blood fats like LDL and triglycerides are associated with a higher risk of heart disease, stroke and heart attack.
Soy has also been found in scientific studies to offer anti-cancer benefits. I'm not going to go into that one in too much depth. It's also been shown to support blood sugar control, which like I say all the time - blood sugar control is extremely important to focus on when you're trying to lose and maintain weight, get rid of cravings and it's also really great to lower your risk of diabetes.
Now, the potential downsides of soy (and I say potential because they are just potential), some people worry because there are things called anti-nutrients in soy. So, soy contains phytates, which are plant-based compounds often categorised as anti-nutrients, alongside lectins, oxalates and tannins.
Anti-nutrients may reduce the availability of minerals like calcium, iron and zinc, however phytates aren't harmful unless your diet is severely imbalanced and you rely solely on soy protein as your main source of iron and zinc. Plus, studies show that your body's absorption of these minerals from plant-based foods is comparable to those from animal products.
Furthermore, you can reduce soy foods' anti-nutrients by soaking, fermenting and cooking. So, quite often with tofu, you're heating it. With so many soy products, they're already fermented or soaked anyway, which actually reduces a lot of the phytates and my point with this, is that unless you're just eating tofu alone or any other form of soy alone, you're still going to be getting iron and zinc from so many other foods if you are eating a varied diet that is rich in whole foods.
So a little tiny negative, like an anti-nutrient that might potentially affect your absorption of some minerals is really nothing to worry about. If you are eating tofu in the context of a diet that has plenty of other vegetables and foods that contain nutrients too.
The other potential downside that people get confused about is the phytoestrogens that are in soy and this always leads to a bit of concern with women that are going through hormonal imbalances or women that are really looking to make sure that they don't get a hormone imbalance, but this is just largely theoretical.
Some people think that soy is bad for you because soybeans contain a high concentration of what's called isoflavones, which are compounds that have a similar structure to oxygen. They are considered phytoestrogens, or plant-derived oestrogen. Some people worry that because of this, eating soy will cause hormonal changes in the body.
Concerns about soy have largely been theoretical, though, like I just said. For example, people worry that if phytoestrogen can act like oestrogen, it might have feminising effects on men or disrupt fertility. Other concerns, like increased risk of breast cancer, thyroid problems and fertility, have been based on animal studies, but it's important to note that animals and humans metabolise isoflavones very differently.
In 2016, the European Food Safety Authority reviewed over 25 years of data in humans and concluded that soy is safe and sometimes beneficial. There is no evidence that soy is bad for you and there is emerging evidence that it may actually help or treat chronic conditions.
So, does soy affect your oestrogen level or fertility? Now, soy does contain isoflavones that look like oestrogen. They can interact with oestrogen receptors in your body however, this interaction tends to be very weak and it doesn't seem to have harmful effects.
Given the possibility of mimicking oestrogen, there have been worries that too much soy could lead to infertility. Studies have found that a high soy diet can prolong the menstrual cycle by 1 day, but it doesn't affect fertility in women and that's when we're looking at a high soy diet.
While some studies have also shown that high intake of soy was associated with lower sperm counts, the more recent meta-analysis that reviewed hundreds of available studies showed no association between soy intake and sperm counts or fertility problems.
To sum that up, there's been a couple of small studies that have potentially suggested that it could affect your hormones, but there's been hundreds of studies that have shown little or no association at all and it's nothing that anyone should worry about.
Please don't fear having tofu a few times a week, soy milk in your coffee sometimes, maybe if you do want to take a little bit of that science and see that it's affecting hormones slightly in some studies, then take it with a grain of salt and go - okay, I'm just not going to fill my entire day, every single day with soy.
It's nothing to worry about if you want to have tofu once a day, soy milk once a day or soy milk, tofu and edamame 3 or 4 times a week. From all of my research and all of the studies, 25 grams of soy protein a day is considered extremely safe and totally fine for you.
That would look like a big serve of tofu in my recipes. For instance - if you're having tofu for dinner in a stir fry, that would have about 20 grams of protein from tofu. So, 20 grams of soy protein. Then let's say you want to have some soy milk in your coffee, that might make it 25 grams a day.
So it's really nothing to worry about and I really want to say this because some people do get concerned about it, but I really want to stress that my 3 Week Body Reset and all the plans that I make in the Health With Bec Tribe have been done after researching things for so long and it is definitely a healthy and balanced way to eat and zooming into a food like tofu really shouldn't be happening. I really hope this is already starting to ease your concerns in that way.
What about soy with your thyroid? This is also something that people can be concerned about too, so I'm going to get into this one in a little bit more depth.
For years, it was thought that eating soy may interfere with thyroid function, possibly inducing hyperthyroidism, which is low thyroid function - it's something that I have myself. In the 1930s, soy was classified as a goitrogen, which is a category of food and supplements that may alter thyroid hormone production and cause the thyroid gland to enlarge.
In the years following, laboratory and animal studies found soy isoflavones affect thyroid hormones in the following ways - prevent the action of thyroid hormones, reduce the absorption of thyroid medications, stimulate thyroid growth leading to goiter or trigger autoimmune thyroid disease, however, human studies have not shown the same results.
In 2019, a meta-analysis of 18 clinical trials found soy had no effect on overall thyroid function. Soy supplementation was linked to a slight rise in thyroid stimulating hormone, but it does not appear to have any clinical significance. In addition, a 2022 review of 417 studies found soy isoflavones do not have a negative effect on thyroid function, thyroid hormone levels or reproductive hormones.In other words, soys reputation as an endocrine disruptor is not supported by the current research.
Too much soy, though, may be a problem. Like anything, too much of any food really isn't good for you, so excessive consumption of soy may alter the action of thyroid hormones, but the mechanism by which these changes occur is still not clear.
A 2016 study published in the Public Health Nutrition, for example, concluded that the chances of having high TSH were quadrupled in people who ate 2 daily servings of soy food versus those who didn't eat any at all, but this effect is likely due to the isoflavones and not the soy itself (a 2018 clinical trial found).
In this study, participants were given either soy protein plus isoflavones or soy protein alone. After 3 months of daily supplementation, only the isoflavone group had elevated levels of thyroid hormones, T3 and TSH. The current research also found women are more susceptible to thyroid problems associated with soy products than men.
For this reason, the different response between men and women, however, is unclear. So from that, there is some evidence to potentially show that excessive soy may slightly interfere with your thyroid function but remember that's excessive.
Let's talk about soy and thyroid medication - if you are on thyroid medication, (it's just something to be conscious of), soy may prevent optimal absorption of thyroid replacement medication. This can cause your medication to provide inconsistent results. So if you take tablets (or however you're taking it), you may not absorb enough of your medication if you're always consuming it with a dairy product.
In general, thyroid medication should be taken on an empty stomach to avoid irregular absorption. Soy containing foods and beverages should also be avoided for around 4 hours before and after taking your dose.
For instance, I always take mine first thing in the morning and the soy products that I personally have would be tofu a couple of times a week and that's not often a breakfast meal for me. If I do occasionally have tofu for breakfast, sometimes I'll still take my medication or sometimes I'll be savvy and wait until lunch time, but regardless, if your medication doesn't get absorbed 100% and it's just once a week or occasionally, it's really not going to throw yourself out of whack too much, so don't overthink it too much.
If you are someone that is drinking soy milk in your coffee in the morning and you're taking your thyroid medication, it might be something to think about, absolutely! You'd want to switch your soy milk to something else and just be conscious to try not to eat soy-based products for 4 hours before and after taking your medication. If it's in the morning, you should be fine, unless you're having it in your coffee or you're eating tofu regularly for breakfast.
Now, because I've gone into excessive soy being potentially harmful for your thyroid, how much soy has been found to be healthy and safe so that it doesn't disrupt your thyroid? This is about 25 grams of soy protein a day. Just a reminder, that's found in tofu, tempeh, miso, edamame beans, soy milk, soy cheese, soy yogurt and soy nuts. The point being, (especially if you're on my meal plans for instance), you are eating that maybe a couple of times a week, some days you don't have any soy at all.
The amount of soy that is in my programs really doesn't need to be of concern. If you have a thyroid condition, it's an absolutely safe amount. In summary, eating soy in moderation does not impact thyroid health, according to the current and latest research.
Excessive soy consumption, however, might alter thyroid hormone levels and interfere with the production of thyroid hormones. I hope that you are not concerned about eating foods like edamame and tofu.
The last thing I want to touch on is the GMO factor, so even though we need far more long-term studies to analyse the effect of GMO foods on your long-term health. It’s very easy to buy tofu that is non-GMO.
Of course, if a food is genetically modified, there can be things like pesticides and glycopyrrolate sprayed which aren't good for you and they have been found to potentially be a carcinogen, but don't let that scare you because you can always just buy non-GMO soy based products.
Soy protein has actually been found to have many benefits and it's far better to focus on those benefits and eating it in moderate amounts, than it is to focus on the small amount of studies that test people that either eating excessive amounts or they're just very outdated science that are tested on rats, so that you can stay on the right track with your health.
It's been found once again to lower cholesterol levels, which reduces your risk for heart disease. Soy has also been found to ease menopausal hot flashes and night sweats. It's been found to lower blood pressure in people with hypertension, it can help with your weight loss, it can help to balance your blood sugars, which in turn will prevent your risk for diabetes and it's overall a fine food to eat. Like anything in excessive amounts it’s probably not going to be great for you.
I really hope you enjoyed it. Please send this to a friend that is concerned about tofu or soy or hormone imbalances or thyroid conditions and if you enjoyed the podcast, please leave me a rating and review. It would mean the world and catch me over on Instagram, which is @health_with_bec for far more health tips and inspiration to help you on your journey to weight loss and weight maintenance and quit the yo-yo dieting.