People with lactose intolerance aren't able to digest milk and other dairy products because their small intestines don't make enough of an enzyme called lactase. Normally, lactase breaks down lactose, or milk sugar, into two single sugars called glucose and galactose, which are absorbed into the bloodstream. Lactose intolerance differs from milk allergy, which is an immune response to the proteins in milk and results in allergic symptoms.
Primary Lactose Intolerance
Lactase production is greatest during early childhood but normally declines after age two. Primary lactose intolerance occurs when lactase production declines to the point where a person can no longer digest milk sugar, usually sometime during adulthood. Less common forms of lactose intolerance include secondary lactose intolerance that occurs as the result of gastrointestinal disease, and congenital lactose intolerance, which is something a baby has at birth.
Symptoms and Diagnosis
The symptoms of primary lactose intolerance include diarrhea, nausea, abdominal cramps, bloating and gas. They usually start 30 minutes to 2 hours after ingesting milk or other dairy products and range from mild to severe, depending upon how much lactose is consumed. Your doctor may diagnose lactose intolerance by having you drink a liquid that contains lactose, then assess your ability to break down the lactose with either a blood test or a hydrogen breath test.
Management
You can't force your body to make more lactase, so you have to make changes in your diet. You may still be able to tolerate small amounts of milk or other dairy products, depending on your tolerance. Lactose-free milk that has lactase added as an ingredient is available in most grocery stores. Over-the-counter lactase products may help you tolerate dairy products if you take them at the same time you consume the dairy products. Your doctor should help you with methods to manage your symptoms and teach you how to identify processed foods that may contain lactose.
Calcium
Milk and dairy products are a major source of calcium, a mineral that your body needs for strong bones and teeth, nerve and muscle function and proper blood clotting. If you avoid dairy products you must find other sources of calcium, such as rhubarb, spinach, soy milk, broccoli, legumes, dark green leafy vegetables and bony fish, or take calcium supplements.
