We’ve all heard the myths around soy - that it’s bad for you in general, causes cancer, infertility and “man boobs” and that you should avoid it at all costs. Luckily, this is all untrue and what is valid (i.e. backed by scientific research) is actually the opposite. Soy is fantastic, particularly for plant-based eaters,  because it’s an amazing source of plant-based protein, full of important nutrients like iron, zinc and calcium, and can possibly help decrease the risk of chronic diseases like heart disease and cancer. Check out my two previous posts about soy: The Truth about Soy, which goes much further into myth busting and general recommendations, as well as 10 Reasons Why You Should Eat Soy with more information about this wonderful legume as well as the best sources of it. 

Hopefully I’ve convinced you that soy should be a staple in your diet for many reasons. To expand even further on the benefits of soy foods, this post dives into whether it’s helpful or harmful for overall gut health. If you’ve ever wondered if your tofu, tempeh or edamame might be hurting your stomach and/or causing bloating, gas and BM issues, read on! 

General Gut Health

Not only is soy beneficial for so many reasons listed above, it’s ALSO great for overall gut health too. Soy has actually been found to increase the good bacteria in the gut, leading to overall better gut health when consumed. This might help explain why soy foods have been associated with healthier outcomes as we are learning more and more about how connected a healthy gut is to an overall healthy body.  One study found that consuming soy products led to an increase in the healthy bacterias bifidobacteria and lactobacilli in the gut. Both of these bacteria have been found to help decrease risk of chronic diseases. Additionally, soy has been found to reduce inflammation as well as improve the cell lining of the gut, both of which lead to a healthier gut and body! 

Another pro for soy is that it is considered to be a prebiotic. Prebiotics are essentially a group of foods that feed the good bacteria in your gut and give them fuel which allows them to thrive. More on this process as well as the difference between prebiotics and probiotics here. 

Speaking of probiotics, one way to get these through foods is to opt for fermented options. Two amazing fermented soy products, miso and tempeh, fall into this category so they’re providing you with the amazing powers of soy PLUS the added benefit of fermentation and good gut bacteria! 

As you can see, soy is generally very beneficial for overall gut health. However, it might cause some digestions for certain people. More on that below. 

Soy & The Low FODMAP Diet

If you suffer from IBS or have had a history of SIBO or other digestive issues, you may be familiar with the low FODMAP diet. If not, check out my series on this topic that delves into it in general as well as how to do it while following a vegan diet (part 1, 2, and 3). Essentially, the low FODMAP diet is an elimination diet that restricts certain carbohydrate-containing foods for a short period of time and then slowly reintroduces them to see if they cause digestive issues. It has been proven to be very effective among individuals with IBS, about 50-70% of those who try it have seen good results.

So this brings us back to soy. What’s interesting…and confusing…about the low FODMAP diet is that some soy products are allowed in the elimination phase while others are not. For instance, extra firm and firm tofu are ok, about a cup of edamame per meal is fine, and tempeh is also acceptable in this phase. This is great news for plant-based eaters going through the low FODMAP diet because a lot of other proteins are restricted like beans and lentils. Also of note is that non-protein soy-based sources like soy sauce, soybean oil, and soy lecithin are also ok to have on the low FODMAP diet.

Conversely, silken tofu, soy milk made from soybeans (which is generally all soy milk sold in the USA), soy flour, soy yogurt, and soy protein powder are all restricted during the low FODMAP diet. This is because the FODMAP content in these particular soy-containing foods is higher than those that are allowed on the diet. This has to do with the manufacturing process and/or water content in these products. Basically, high FODMAPs can irritate individuals with IBS, which can cause the uncomfortable side effects they experience such as bloating, gas, constipation and/or diarrhea. 

To tie this all together, if you have IBS or suspect that you do, you may want to look at which types of soy you’re consuming. For instance, if you mainly drink soy milk, but notice that your stomach is upset on the days that you do, try cutting it out for a week or two and see if this helps. You can then reintroduce it and see if your symptoms come back. 

Soy Allergy

Soybeans are one of the top 8 food allergens which means it's considered one of the most common food allergies. However, data suggests that most people born with a soy allergy will outgrow it by the time they’re 3 years old and that there is a very small percentage of adults with a soy allergy There are many ways a soy allergy can present itself, the most serious being anaphylaxis. Less serious signs include hives, tingling of the mouth, swelling of the lips, and digestive issues like stomach pain, diarrhea, nausea and vomiting. If you believe soy causes digestive issues for you, there is a possibility, though small, that you have a true allergy to soy. If you do suspect this, get tested from an allergist that is a licensed medical doctor. I do not suggest doing a food sensitivities test as there is very limited scientific evidence behind them and they can often give false positive results. 

Ways to Increase the Benefits of Soy

Bearing no issues with FODMAPS or allergies, soy is something that should be celebrated and eaten often (in fact I recommend multiple servings daily) particularly if you are plant-based, vegetarian or vegan. To reap all the benefits of soy products, particularly from a gut health and nutrient perspective, there are ways to boost the powers of it. As mentioned, choose a fermented version, like tempeh or miso, often for the natural probiotics they provide. Second, for added gut healthy benefits, pair your soy products with fiber-rich foods like beans, lentils, avocado, quinoa, brussel sprouts, and broccoli. Third, pair your soy products with a source of vitamin C as this will help you absorb both the iron and zinc found in some foods like tofu and tempeh. Foods that pair well that fall into this category are bell peppers, lemon juice, tomatoes, potatoes and broccoli. 

Bottom Line

We’ve previously established that soy foods can be so positive for overall health and are great for plant-based eaters because of their wonderful source of protein, vitamins and minerals, and help with decreasing the risk of chronic diseases. Now we can add the gut health boosting powers of soy to this list too. If you feel that soy is a potential trigger for GI issues, I highly encourage you to make an appointment with a gastroenterologist, a registered dietitian, and possibly an allergist to help figure out what’s going on. There might be a chance you have IBS, a true soy allergy, or something else going on. If you tolerate soy just fine, I hope you’re able to fully enjoy a daily dose of it through soy milk, tempeh, tofu, edamame, soy curls, and miso covered dishes.