Andreas Moritz
Dear Danielle,
Due to the large amount of enzyme inhibitors and anti-nutritient compounds - antigrowth factors - there is a limit as to how many legumes humans and animals can eat without suffering digestive problems. The normal cooking process of up to several hours for most beans does not entirely destroy them. Also, there are a variety of other compounds in beans that cause gas. Mainly, these are the non-digested carbohydrates raffinose, stachyose, and sometimes verbascose, which provide substrate for intestinal microflora to produce flatus.
Most the legumes' enzyme-inhibitors, which protect the plants against insect attacks or fungal infestation, are not fully denatured by normal cooking processes. For example, the protein alpha-amylase inhibitors may represent as much as 1% of wheat flour and, because of their heat resistance, they persist through bread-baking, being found in large amounts in the center of loaves. For that reason, when people eat a lot of the inner parts of bread, instead of the crusty parts, they tend to develop flatulence.
The problem with the legume soybean is even more pronounced than found with other legumes or grains. In soy products, because of the necessity of achieving a balance between the amount of heat necessary to destroy the enzyme inhibitors and that which may result in damage to the nutritional properties of soy, most commercially available edible-grade soybean products retain 5 to 20% of the enzyme inhibitor activity (for trypsin) originally present in the raw soybeans from which they were prepared. This means that soy products have a toxic effect onn the body, and should not be consumed on a regular. Likewise, eating other legumes more often than 1-2 times per week can impair immune functions and cause GI-tract disturbances.
Yellow mung beans (dahl), if soaked for 30-60 minutes prior to cooking (30-40 minutes cooking time) contain the least amount of these compounds and are the easiest to digest. But, once again, the rule of thumb is to not eat them more often than 1-2 times per week.
Andreas