Lactose is the main sugar in milk. Normally when lactose reaches the small intestine, it is broken down into simpler sugars by the enzyme lactase. These simpler sugars are absorbed into the bloodstream and eventually are used as fuel for he body.
Lactase is made in the cells that line the small intestine. In some people, these cells do not make enough lactase. In a few people, they do not make any at all. When people do not make enough lactase, they cannot digest some portion of the lactose they have eaten.
Lactose that is not broken down cannot be absorbed into the blood. Instead, it remains in the large intestine (colon) where bacteria convert it into lactic acid. Lactic acid is a laxative and an irritant to the colon.
Lactose intolerance is an extremely common condition. It rarely develops before age six, and is due to a genetically programmed decline in lactase. This decline begins around age two, the age when most infants have finished the transition from breast milk to solid food.
In some people this decline continues to the point where in late childhood or early adulthood they develop lactose intolerance symptoms.
Although the greatest quantities of lactose are found in milk and dairy products, milk is used in the preparation of many processed foods such as chocolate bars, puddings, and soups.
Food labels must list all the ingredients in processed foods. Lactose intolerant individuals should look for these words on the label that indicate the presence of lactose: milk, condensed milk, whey, curds, milk-by-products, dry milk solids.
Lactose is found in other unlikely places such as:
-bread and baked goods and biscuit, pancake, and cookie mixes
-processed breakfast cereals and breakfast drinks
-instant mashed potatoes
-lunch meats (except kosher meats which are lactose- free)
-salad dressings
-all chocolate candies, caramels, butterscotch, and many others
-as filler in medications. As many as 6% of prescription and over-the-counter drugs contain lactose.
The amount of lactose found in these hidden sources is not enough to affect most people, but for the severely lactose intolerant, it can be enough to cause symptoms and make meal planning a necessity and eating out difficult.
Many individuals diagnose themselves as lactose intolerant using an elimination diet. However people who think they may be lactose intolerant should see their physician because the symptoms of lactose intolerance can be quite similar to those of more serious and sometimes progressive diseases such as celiac disease (a gluten intolerance), Crohn’s disease, giardia (a parasitic infection of the bowel), and inflammatory bowel disease.
Lactose intolerance can be diagnosed by giving the individual lactose and then measuring changes in the sugar (glucose) level in their blood. In lactose intolerant individuals lactose is not broken down into sugars that can be absorbed from the intestine. Therefore, the level of glucose in the blood will be lower than expected. Lactose can also be diagnosed by a hydrogen breath test.
