In fact, they are even beneficial to digestion. However, bacteria rely on carbohydrates and sugars for their nutrition. In the process of breaking down these nutrients, bacteria generate gases such as hydrogen, carbon dioxide, and methane. Under normal conditions, many of these gases are reabsorbed and do not cause excessive flatus. Carbohydrates and sugars are normally digested and absorbed in the stomach and small intestine.
Some people have disorders that interfere with the normal digestive process.
For example, lactose is a sugar found in milk. It requires the enzyme lactase for digestion. A person with lactase deficiency may not be able to digest lactose properly. These abnormalities in digestion allow carbohydrates and sugars to pass undigested into the colon, where gas forming bacteria thrive on them. Some foods, such as legumes, cabbage, or certain types of bran contain carbohydrates that the body cannot digest.