What is lactose intolerance?

Lactose intolerance is the inability to digest lactose, the sugar primarily found in milk and dairy products. It is caused by a shortage of lactase in the body, an enzyme produced by the small intestine that is needed to digest lactose. While lactose intolerance is not dangerous, its symptoms can be distressing.

Who is affected by lactose intolerance?

For most people, lactose intolerance develops over time as the body produces less lactase.

It is estimated that 36% of Americans and 68% of the world population have some degree of lactose intolerance. Lactose intolerance affects people from certain ethnic populations and races—such as Latin Americans, African-Americans, Native Americans, Asians, East Europeans and Middle Easterners—more than others.

How do I know if processed foods contain lactose?

When buying food, read the ingredients on food labels carefully. Ingredients derived from milk that contain lactose include:

  • Whey.
  • Cheese.
  • Milk by-products.
  • Dry milk solids.
  • Lactose.
  • Butter.
  • Curds.
  • Nonfat dry milk.
  • Dry milk powder.

Also avoid items that state "may contain milk" on the food label. Depending on the severity of your symptoms, you may need to avoid or limit foods containing these ingredients.

The following ingredients come from milk and do not contain lactose:

  • Casein
  • Lactalbumin
  • Lactate
  • Lactic acid

Lactose is also present in about 20% of prescription medications, such as birth control pills (oral contraceptives), and about six percent of over-the-counter medications, such as some tablets for stomach acid and gas. Viactiv® calcium chews contain lactose and should be avoided while following a lactose-free diet.

These medications usually affect only people with severe lactose intolerance. Ask your healthcare provider which medications contain lactose, and read the labels on over-the-counter medications to check their lactose content.

Foods that contain lactose in small quantities include:

  • Bread and baked goods.
  • Milk chocolate and some candies.
  • Salad dressings and sauces.
  • Breakfast cereals and cereal bars.
  • Instant potatoes, soups, rice and noodle mixes.
  • Lunch meats (other than kosher).
  • Cheese flavored crackers and other snacks.
  • Mixes for pancakes, biscuits, and cookies.
  • Margarine and butter.
  • Organ meats (such as liver).
  • Sugar beets, peas, lima beans.
  • Certain coffee creamers.

What causes lactose intolerance?

Lactose intolerance is caused by a shortage of lactase in the body, an enzyme produced by the small intestine that is needed to digest lactose. Certain digestive diseases (such as Crohn’s disease, ulcerative colitis, and celiac disease), stomach or intestinal infections, and injuries to the small intestine (such as surgery, trauma, chemotherapy, or radiation therapy) may reduce the amount of lactase available to process lactose properly. If the small intestine is injured, lactose intolerance may be temporary, with symptoms improving after the intestine has healed.

What are the symptoms of lactose intolerance?

Symptoms of lactose intolerance include nausea, cramps, gas, bloating, or diarrhea within 30 minutes to 2 hours after consuming milk or dairy products. Symptoms occur because there is not enough lactase being produced by the body to digest the lactose consumed. The severity of symptoms varies, depending on the amount of lactose an individual person can tolerate. Some people may be sensitive to extremely small amounts of lactose-containing foods while others can eat larger amounts before they notice symptoms.

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