Lactose Intolerance

Lactose intolerance is a difficulty properly digesting lactose (milk sugar) and the various dairy products that contain lactose. It is very common with an estimated 30-50 million Americans affected, especially African Americans, Native Americans, and Mexican Americans. Lactose intolerance causes various digestive symptoms, usually after meals, including cramps, bloating, gas, and diarrhea.
The condition resulting from the absence or deficiency of LACTASE in the MUCOSA cells of the GASTROINTESTINAL TRACT, and the inability to break down LACTOSE in milk for ABSORPTION. Bacterial fermentation of the unabsorbed lactose leads to symptoms that range from a mild indigestion (DYSPEPSIA) to severe DIARRHEA. Lactose intolerance may be an inborn error or acquired
Congenital disorder consisting of an inability to digest milk and milk products; absence or deficiency of lactase results in an inability to hydrolyze lactose

Causes and symptoms

Causes: Lactose Intolerance: cannot digest lactose because you do not have enough lactase enzyme. The small intestine needs lactase enzyme to break down lactose. If lactose is not digested, it can cause gas and stomach cramps.
Even though lactose intolerance is not a dangerous health condition, the symptoms can be very uncomfortable. Gas, bloating, stomach cramps, diarrhea, and nausea are the most common symptoms. These symptoms may begin within as little as 30 minutes or up to two hours after eating or drinking foods that contain lactose. The severity of symptoms is different for each person, and depends on how much lactose a person can tolerate. Recent studies have found that many people who have lactose intolerance can have one serving of milk with a meal or two servings of milk per day, at separate times, without experiencing symptoms. People also may be able to tolerate food like aged cheese, which has less lactose, or yogurt, which has bacteria that digests lactose. Some experts believe that people who are sensitive to milk products, but can digest them in small quantities without experiencing severe gastrointestinal symptoms, are not lactose intolerant, but have lactose maldigestion. These people may produce lactase in very small amounts, but enough to allow them to digest very small amounts of dairy products.

How is lactose intolerance diagnosed?

Lactose intolerance can be hard to diagnose based on symptoms alone. People sometimes think they suffer from lactose intolerance because they have the symptoms associated with the disorder, not knowing other conditions such as irritable bowel syndrome can cause similar symptoms. A doctor can use tests to diagnose lactose intolerance but may first recommend eliminating cow’s milk from the diet to see if the symptoms go away.
The most common tests used to measure the absorption of lactose in the digestive system are the lactose tolerance, hydrogen breath, and stool acidity tests.

  • The Lactose Tolerance Test. This test requires fasting (not eating) before the test and then drinking a liquid that contains lactose. Several blood samples are then taken over a 2-hour period to measure the person’s blood glucose (blood sugar) level. These measures indicate how well the body is able to digest lactose. Normally, when lactose reaches the digestive system, the lactase enzyme breaks it down into glucose and galactose. The liver then changes the galactose into glucose, which enters the bloodstream and raises the person’s blood glucose level. If, however, lactose is incompletely broken down, the blood glucose level does not rise and a diagnosis of lactose intolerance is confirmed.
  • The Hydrogen Breath Test. This test measures the amount of hydrogen in a person’s breath. Very little hydrogen is normally detectable. However, undigested lactose in the colon is fermented by bacteria and produces various gases, including hydrogen. The hydrogen is absorbed from the intestines, carried through the bloodstream to the lungs, and exhaled. In this test, the person drinks a lactose-loaded beverage and the breath is analyzed at regular intervals. Raised levels of hydrogen in the breath indicate improper digestion of lactose. Certain foods, medications, and cigarettes can affect the accuracy of the test and should be avoided before taking the test. People should check with their doctor to make sure they are not taking medications that may interfere with test results.
  • The lactose tolerance and hydrogen breath tests are not given to infants younger than 6 months of age. A large lactose load can be dangerous prior to this age, as infants are more likely to become dehydrated from diarrhea that can be caused by lactose intolerance.
  • Stool Acidity Test. This test may be used for infants and young children to measure the amount of acid in their stool. Undigested lactose fermented by bacteria in the colon creates lactic acid and other fatty acids that can be detected in a stool sample. Glucose may also be present in the sample as a result of unabsorbed lactose in the colon.

Where is lactose hidden?

Although milk and foods made from milk are the only natural sources of lactose, it is often added to prepared foods. People with very low tolerance for lactose should know about the many food products that may contain even small amounts of lactose, such as:

  • bread and other baked goods.
  • processed breakfast cereals.
  • instant potatoes, soups, and breakfast drinks.
  • margarine.
  • lunch meats (other than kosher).
  • salad dressings.
  • candies and other snacks.
  • mixes for pancakes, biscuits, and cookies.
  • powdered meal-replacement supplements.

Some products labeled non-dairy, such as powdered coffee creamer and whipped toppings, may actually include ingredients that are derived from milk and therefore contain lactose.
Learn to read food labels with care, looking not only for milk and lactose, but also for words such as whey, curds, milk by-products, dry milk solids, and non-fat dry milk powder. If any of these words are listed on a label, the product contains lactose.
Lactose is also used in more than 20 percent of prescription drugs and about 6 percent of over-the-counter medicines. Many types of birth control pills contain lactose, as do some tablets for stomach acid and gas. However, these products typically affect only people with severe lactose intolerance.

Tips

  • Choose lactose-reduced or lactose-free milk.
  • Take a lactase enzyme supplement (such as Lactaid) just before you eat dairy products. These can be taken in drops or tablets and even added directly to milk (they tend to make milk taste a bit sweeter if left for a long time).
  • When you do drink milk or eat lactose-containing foods, eat other non-lactose foods at the same meal to slow digestion and avoid problems. (For example, if you are going to have a milkshake, don’t drink it by itself. Have something else with it — like a healthy sandwich.)
  • Drink juices that are fortified with calcium.
  • Eat a variety of dairy-free foods that are rich in calcium, such as broccoli, beans, tofu, or soy milk. Consider hard cheeses such as cheddar, which are lower in lactose.
  • Yogurts that contain active cultures are easier to digest and much less likely to cause lactose problems.
  • Learn to read food labels. Lactose is added to some boxed, canned, frozen, and prepared foods like bread, cereal, lunchmeats, salad dressings, mixes for cakes and cookies, and coffee creamers. Be aware of certain words that may mean the food has lactose in it: butter, cheese, cream, dried milk, milk solids, powdered milk, and whey, for example.

What about yogurt?

Yogurt may be safe. Some studies have shown that the active live bacterial cultures (also known as probiotics) found in yogurt help lactose digestion. However, frozen yogurt does not seem to have the same effect for many people, and may still cause stomach upset.
Buttermilk and acidophilus milk, although fermented, still cause as much distress in most people as plain milk. As everyone’s level of lactase deficiency is different, sometimes you really do not know whether you can tolerate a specific product until you try drinking it.

Congenital causes

Lactase deficiency may occur because of a congenital absence (absence from birth) of lactase due to a mutation in the gene that is responsible for producing lactase. This is a very rare cause of lactase deficiency, and the symptoms of this type of lactase deficiency begin shortly after birth.

What is new in lactose intolerance?

It is now possible to test the DNA of individuals to make a diagnosis of lactose intolerance. This is likely to be an important research tool for studying lactase deficiency and lactose intolerance. It is still too early to know how helpful this sophisticated testing will be in the clinical evaluation and treatment of patients. It is an expensive test.
In 1998, scientists were able to make lactose intolerant rats tolerant of lactose by transferring the gene for lactase to their intestinal lining cells. It is unlikely that this type of gene therapy will find much of an application in people. Nevertheless, it is a fascinating example of what science can accomplish.

Sources: Wrong Diagnosis, Kids health

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