Confused about soy products and the low FODMAP diet? You’re not the only one! Soy beans and soy products can contain high levels of oligosaccharides (mainly GOS but sometimes fructans). However, it’s a myth that you need to avoid all soy products while on the low FODMAP diet. Manufacturing processes can greatly reduce the FODMAP content of soy products, which is why some are low FODMAP and others are not!
Low FODMAP Soy Options
Soy Milk Made From Soy Protein
Soy milk made from soy bean protein is low FODMAP and it is a great option if you are looking to replace cow’s milk (1). However, be aware that whole soybean milk is high FODMAP, so you will need to check the ingredients list to see if the milk is made from just soy protein. According to Monash University soy milk made from soy protein is safe to have in 250ml (or 1 cup) serves FODMAP (1). Soy milk made from soy protein is much easier to find in New Zealand and Australia.
Regular tofu is made from curdling fresh soy milk and pressing the curds into block moulds (2). It is commonly known that soybeans are high FODMAP, so you might be wondering why regular tofu is low FODMAP. We know that FODMAPs, especially GOS and fructans, are water-soluble (3). During manufacturing regular tofu is pressed, which reduces the water content and drains out some of the GOS (galacto-oligosaccharides), making it low FODMAP (3). The firmer the tofu is, the less water content it has, and in theory the lower in FODMAPs it will be. Just remember to drain your regular tofu well. According to Monash University, a low FODMAP serve of tofu is 170g (1).
Please note that silken tofu is high FODMAP and you will need to avoid it during the low FODMAP phase of the diet.
Tempeh is made from cooked soy beans that have been slightly fermented (4). The fermentation of the soy beans reduces the FODMAP content down to levels within the low FODMAP threshold (5). Tempeh is firmer and more flavourful than tofu and it has a slightly nutty taste.
Soy sauce is made using fermented soybeans. It is possible that the fermentation process reduces the oligosaccharides in the soybeans, which is why the soy sauce is low FODMAP. Soy sauce is low FODMAP in 2 tablespoon serves (1).
Fresh Edamame (1 cup or 50g)
Edamame are young (immature) green soy beans that are eaten fresh, unlike the hard, dry mature soy beans which are used to make tofu and soy milk. The edamame beans (just the beans not the pods) are low FODMAP in serves of 1 cup (50g). If you are not sure how to use edamame beans then check out my Low FODMAP Asian Hot & Sour Soup, which was published by Monash University in 2016.
Soybean oil is highly processed and does not include any carbohydrate content. This means it is low FODMAP, along with all other oils.
Soy lecithin is made during the production of soybean oil. It consists of a mixture of fat and oil (not carbohydrates), which means it is considered low FODMAP, although it hasn’t officially been tested by Monash University. Also keep in mind that only small amounts of soy lecithin are used in processed products, which makes it unlikely that it will increase the overall FODMAP level within the products. You can find out more about soy lecithin here.
FODMAP Content Varies
Soy Protein Powder
Soy protein powder is made from defatted soybean flakes that are processed to remove some of the oligosaccharide content. According to Monash University, soy milk made from soy protein is low FODMAP (1). So it is possible that some soy protein powders might be low FODMAP, however, that will depend on how it has been processed. More testing is still needed to understand the FODMAP content in soy protein powders. In the meantime, if you do decide to use soy protein powder, choose soy protein isolate powder that contains low amounts of fibre or no fibre content (the oligosaccharides hide in the soybean fibre), then test your tolerance to a small serve.
The FODMAP content of soy yoghurt is likely to vary depending on the type of soy milk used. Ideally look for a soy yoghurt which is made from soy protein, otherwise you might want to test your tolerance levels to a small serve first.
High FODMAP Soy Products
Silken tofu is unpressed, which means, unlike regular tofu, the water and FODMAP content is not drained out of the tofu. According to Monash University silken tofu is high FODMAP for GOS (oligosaccharides) (1).
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Soy Milk made from Whole or Hulled Soy Beans
Soy milk made from whole or hulled soy beans have higher levels of FODMAPs compared to soy milk made from soy protein. These milks are generally considered high FODMAP, however, you can enjoy a small 60ml serve of soy milk made from hulled soya beans, or a 30ml serve of soy milk made from whole soya beans (1).
Boiled soy beans (these are mature soy beans) are high FODMAP for both GOS and fructans at small ¼ cup serves (1). This means it is advised that you avoid them during the low FODMAP phase.
Soy flour is popular in gluten free products. It has been tested by FODMAP Friendly and it is high FODMAP for fructans and GOS in 50g serves. This means you should avoid large serves during the low FODMAP phase of the low FODMAP diet. You might find you can tolerate 1 to 2 slices of gluten free bread that contains soy flour, providing it isn’t the predomination flour (eg listed in the first 3 ingredients), so it can be worth exploring your tolerance levels.
Just remember that the low FODMAP diet is not a soy free diet! You can enjoy a range of soy based products like soy protein milk, regular tofu, tempeh, soy sauce, miso, and edamame. Just remember to check the Monash Low FODMAP app and FODMAP Friendly App for serving size guidelines.