Soy foods can be an important source of protein and other nutrients for vegetarians and vegans. In addition, adding soy can be a way to break away from the routine of eating animal protein and add more plant-based protein for everyone else. But can soy foods be part of a low FODMAP diet? Let’s find out.
Soy and FODMAPs
Soybeans are indeed a source of FODMAPs – mostly galacto-oligosaccharides (GOS) and some fructans. Therefore, they are not included during the elimination phase. However, many of the products made from soybeans become low FODMAP because of what happens during their processing.
The FODMAP status of soy depends on… the processing
That’s because FODMAPs are soluble in water. If the final product retains the water, it is high in FODMAPs. But if the water is strained, the soy product becomes low in FODMAPs. For example, soy milk from whole soybeans is made by grinding the beans and water together. Therefore, it’s considered high in FODMAPs. The same is true for soy yogurt, as it is made from soy milk. Incidentally, there is a type of soy milk made from soy protein that is low in FODMAPs. It is popular in Australia but here in the US, it is not as easy to find. The only brand I came across is 8th Continent but all their varieties are high in sugar and one of them also contains inulin, a fructan.
On the other hand, any technique that involves soaking the soybeans in water and straining them will allow the FODMAPs to leach into the water and considerably lower the FODMAP content of that food. This is the case with firm tofu, but not with silken tofu. The water is not drained and the tofu retains all the FODMAPs.
Another food processing technique that lowers FODMAP content is fermentation. This explains why plain tempeh (made from fermenting soybeans) is low in FODMAPs. Some tempeh varieties also have grains like rice or millet but most are free of wheat/gluten (just avoid those with barley, a high-FODMAP grain). Watch out for added high-FODMAP ingredients like garlic, onions, or celery.
A second consideration when choosing soy products is that GOS and fructans are fibers, and foods that are lower in fiber are also lower in FODMAPs. Immature soybeans – edamame – are an example. They are low FODMAP in moderate amounts.
Soy food derivatives
Soy burgers or meat substitutes have not been tested but most are likely to be high in FODMAPs as they may contain the fibers from soybeans. Textured soy protein, the main ingredient in many soy-based meat substitutes is high in FODMAPs.
Soy protein powder may be low in FODMAPs depending on the processing. It is best to avoid it during the elimination phase as its FODMAP status is unknown.
Soy lecithin and soybean oil are not a source of FODMAPs and are ok. Soy sauce is also low in FODMAPs.
How to choose soy foods on a low FODMAP diet
In summary, use this guide to navigate the soy aisle, and don’t be afraid in experimenting with soy foods.
Low FODMAP soy foods
- Tofu (firm or extra firm)
- Plain Tempeh (no extra high FODMAP ingredients)
- Soybean oil
- Soy sauce
High FODMAP soy foods
- Soy milk (made from soybeans)
- Soy yogurt
- Silken tofu
- Soy burgers/meat substitutes
- Textured soy protein
- Soy protein powder
Check out the Monash University FODMAP App for appropriate serving sizes.
In summary, soy can certainly be part of a low FODMAP diet and foods like edamame, tofu, and tempeh can be an excellent source of protein and other important nutrients, as well as a way to vary your diet. If, after reintroducing GOS and fructans, you find you tolerate them, you can experiment with the high-FODMAP soy foods as well.