When the undigested bits of food reach the colon, they are fermented by the bacteria that live in the colon, causing gas. Today, many people are trying to improve their nutrition and health by eating more fiber. However, some people discover that adding large amounts of fiber to their diets causes gassiness. They get a feeling of being bloated when they first begin the high-fiber diet, but within three weeks or so, they may adapt to it. Some people, however, don't adapt, and the bloating from eating a lot of fiber can be a permanent problem.
Lactase is needed to digest lactose, the sugar found in milk and other dairy products.
When this sugar passes undigested into the colon, it is fermented by bacteria, and gas forms. This can be a cause of excessive flatulence. If lactase deficiency is suspected of causing your gas, your doctor may tell you to stop eating dairy products for a while to see if you will have less gas. The doctor also may give you a blood test or a breath test to find out if you are lactose intolerant. The breath test detects hydrogen that is released by the bacteria as the undigested lactose ferments in the colon.