Lactose is a sugar found in the milk of humans and other mammals. The ability to digest milk occurs because lactase, an enzyme that’s produced in the small intestine, breaks down lactose into two simple sugars, which are then used by the body. When there is an insufficient amount of lactase, unabsorbed lactose moves to the colon where the bacteria cause it to ferment, leading to bloating and gastrointestinal discomfort.

Virtually all human infants depend on milk for survival and digest the nutrients in it, including lactose. But early in childhood, most people start producing less lactase and consequently cannot digest more than a small amount of milk. In these people, who are termed lactose intolerants or lactose maldigesters, drinking milk (especially drinking it in the absence of food) can produce uncomfortable symptoms—such as gas, stomach cramps, and diarrhea—within 30 minutes to two hours. (A few people, including infants, may be allergic to the protein in milk, but that’s not lactose intolerance.)

There are degrees of tolerance and intolerance for milk; in fact, not all lactose intolerants have to give up milk consumption. Although the ability (or loss of ability) to digest lactose is an inherited trait, drinking habits also depend on custom and preference.

Many Americans who believe they are lactose intolerant are mistaken: The prevalence of lactose intolerance is overestimated, according to a review in the Journal of the American Dietetic Association. But the extent of the problem varies widely among different racial and ethnic groups. Only 15 percent of white Americans are affected by some degree of lactose intolerance; the proportion of African-Americans affected is significantly higher at 60 to 80 percent. The problem occurs with varying severity in about 90 percent of Asian-Americans, 65 to 100 percent of Native Americans, and about 50 percent of Mexican-Americans. Up to 75 percent of adults worldwide may be affected.

Symptoms of Lactose Intolerance

  • Abdominal pain, cramps, and bloating within a few hours of consuming milk or milk products
  • Nausea
  • Excessive gas
  • Diarrhea
  • “Grumbling” abdomen and bowel

What Causes Lactose Intolerance?

While some infants are born with the ailment, lactose intolerance usually develops in childhood beginning at two to five years of age. The production of lactase then steadily decreases until adolescence and remains at low levels throughout life. The ailment can also develop later in life because of chronic digestive disorders such as irritable bowel syndrome, Crohn’s disease, or celiac disease. In both adults and children, a temporary form of lactose intolerance may occur owing to illness (such as gastroenteritis) or side effects of medication (such as antibiotics or NSAIDs like ibuprofen) that affect the intestinal lining and stop lactase production for a few weeks.

What If You Do Nothing?

Lactose intolerance is not a health risk. But if you are truly lactose intolerant, symptoms can occur whenever you consume milk and other dairy products high in lactose. (However, the amount that you consume makes a difference in how much discomfort you experience.)

Home Remedies for Lactose Intolerance

Lactose intolerance cannot be cured, but once lactase deficiency has been diagnosed, there are strategies you can use to avoid or control its symptoms. The most obvious step is to eliminate all dairy products from your diet. However, this is not only difficult for most people but also often unnecessary. Instead, first follow the measures below (including turning to nondairy sources of calcium in your diet if you do reduce your consumption of dairy products).

  • Be sure you are truly lactose-intolerant. Bloating, flatulence, and stomach cramps aren’t always caused by lactose intolerance; it’s not a condition that develops suddenly. You can do a simple test for lactose intolerance at home. Drink two glasses of skim milk on an empty stomach and see if symptoms such as bloating, gas, and diarrhea occur during the next three to four hours; this suggests lactase deficiency is probably the cause. If so, repeat the test using lactase-treated milk. If you then experience no symptoms, you probably have lactose intolerance. But if you have chronic gastrointestinal discomfort, see a doctor for further testing.
  • Consume small portions of milk and milk products. You can eliminate dairy products from your diet, but not only is that difficult, it often isn’t necessary. While many people can’t tolerate large portions of dairy products, they have no problems with smaller servings. In fact, studies have shown that many true lactose maldigesters (classified as such by laboratory tests) can consume moderate amounts of milk and dairy products without symptoms, particularly if the milk is part of a meal. Whole milk causes fewer problems than skim, because its fat slows the rate of stomach emptying.
  • Eat dairy products along with food. This will slow the emptying of the food from the stomach into the intestine, where lactose is digested, and decrease or eliminate symptoms. This strategy allows more time for the available lactase to act upon the lactose-containing food.
  • Try active-culture yogurts. Fermented milk products such as yogurt with active cultures are usually easier to digest than milk. Most yogurt is low in lactose anyway, and the bacteria in it help break down what milk sugar there is. But as much as 30 to 70 percent of the lactose originally in the milk may remain in the yogurt. For lower lactose, look for yogurt that states “Live and Active Cultures” on the label—or just experiment until you find a brand that agrees with you.
  • Cheese is all right. There should be no problems with cheese, especially hard, aged cheeses like Swiss, Parmesan, and Cheddar, since most lactose is removed along with the whey when the cheese is made.
  • Give soy milk a try. This product made from soybeans may be poured on cereal, used for cooking, and consumed as a beverage by infants and adults. Acidophilus milk or buttermilk may not be any better for people sensitive to lactose; the degree of fermentation is variable, and so lactose content also varies.
  • Consider using lactose-reduced and lactase products. If the other strategies don’t work for you, try lactose-reduced milk, which is available in most markets. This type of milk contains about 70 percent less lactose and tastes sweeter than regular milk. You can also buy lactase tablets or liquid in drugstores or grocery stores and add them to the milk yourself; five drops per quart can break down over 70 percent of the milk sugar in about 24 hours (for greater reduction, let the treated milk stand for 48 to 72 hours). If you add drops to commercially treated milk, you can eliminate nearly all the lactose. You can also swallow lactase tablets or capsules just before you consume a milk product, but that’s usually much less effective than adding drops to the milk itself.
  • Read labels carefully. The Food and Drug Administration (FDA) doesn’t require food companies to label their products “lactose free.” Limit or avoid foods containing milk (nonfat milk as well), lactose, whey, dry milk solids, and milk curds. Lactose may be added to prepared and processed foods, including baked goods, breakfast foods, luncheon meats, salad dressings, and soups. Some artificial sweeteners may also contain lactose.
  • Increase the calcium in your diet. If you eliminate or drastically cut back on dairy foods, you must compensate for the lack of calcium and other essential nutrients.

Lactose-Intolerant Children

Lactose intolerance, an inability to break down and absorb sugars found in milk and milk products, is common in infants. A few are born lactase-deficient, but at ages three to five, the incidence increases and about 75 percent of all children worldwide have decreased levels of lactase; an estimated 15 percent of all American school children are thought to be lactose-intolerant. When milk or milk products are ingested by lactose-intolerant children, symptoms develop within eight hours and include explosive watery diarrhea, abdominal distention, and flatulence.

To find out if your child is lactose-intolerant, a physician will first perform a physical examination. The child may then be asked to consume specific foods and the subsequent stool will be analyzed for unabsorbed substances.

Once lactose intolerance has been confirmed, the physician will recommend a reduction of milk and milk products in the child’s diet, along with some of the measures described on these pages—including giving the child soy protein formula, milk products with added lactase, or special lactase supplements that you add to the milk products to aid in digestion.

You can also try adding yogurt and cheese to the child’s diet. These fermented foods are lactose-reduced and consequently may have no negative effects, while offering an excellent source of calcium, vitamin B2 vitamin D, and protein.


There is no way known to prevent the condition of lactose intolerance, but the self-care approaches discussed above can prevent symptoms.

Beyond Home Remedies: When To Call Your Doctor

Contact your physician if self-treatment measures don’t provide relief for you (or for your child) and you continue to experience gastrointestinal discomfort. For infants, call your doctor if your baby fails to gain weight or refuses food or formula. If the infant is on a doctor-recommended milk-free diet, be sure to contact the doctor if the diet does not relieve symptoms.

What Your Doctor Will Do

After taking a history, your physician may order a breath hydrogen test to confirm lactose intolerance. Based on the findings, your physician will make recommendations to reduce or eliminate certain foods.


The Complete Home Wellness Handbook

John Edward Swartzberg, M.D., F.A.C.P., Sheldon Margen, M.D., and the editors of the UC Berkeley Wellness Letter

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 11 Aug 2010

Last Modified: 23 Dec 2014