Soy foods are a good source of protein for those on a vegetarian diet, but some people claim it causes bloating and gas. Is soy hard to digest?
One of the problems frequently encountered with eating a vegetarian diet is the problem of getting adequate protein. To meet the body’s protein requirements, many vegetarians turn to soy based foods such as tofu, soy milk, and fermented soy products such as miso and tempeh. One concern about eating soy based products is their effect on digestion. People who eat large quantities of soybean based foods complain of bloating, flatulence, and indigestion in greater numbers than people who eat meat based protein. Is soy hard to digest?
There are actually two factors that play into soy’s digestibility. Soy, like most legumes, contains compounds known as trypsin inhibitors. Trypsin is an enzyme produced by the pancreas that’s important for protein digestion. Without the action of trypsin, protein doesn’t get completely broken down or digested. This can lead to symptoms of gas, bloating, and generalized indigestion.
Another reason soy is hard to digest is that it contains the oligosaccharides raffinose and stachyose. These are the same indigestible carbohydrates found in beans, another big gas promoter. In some soy based foods, the oligosaccharides have been removed, but in many soy products, such as soy flour, significant quantities remain. Unfortunately, cooking soy foods doesn’t make them any more digestible since the oligosaccharides aren’t broken down by heat. People vary in their degree of tolerance to soy foods. Some people have no problems eating them, particularly in smaller amounts, but when larger quantities are eaten especially in conjunction with an overall high fiber diet, indigestion and gas may result.
There is one potential solution to the poor digestibility of soy. Fermented soy foods such as miso and tempeh usually have lower levels of trypsin inhibitors and indigestible oligosaccharides and may give fewer symptoms. Tempeh is also higher in protein and fiber than tofu and has a firmer texture which makes a good meat substitute. Even people who experience gas and bloating after eating other legumes can often eat fermented soy products such as tempeh and miso without a problem. Fermented soy products also lack the phytates that can inhibit the absorption of minerals such as calcium and iron
The bottom line? If you’re looking for a vegetarian source of protein and find unfermented soy hard to digest, try tempeh and miso. They’re a good source of protein and may cause less intestinal discomfort.