Lactose Intolerance

Lactose intolerance is the condition in which lactase; an enzyme needed for proper metabolization of lactose is not produced in adulthood.

Lactose is a constituent of milk and other dairy products.

The result of consuming lactose or a lactose-containing food for individuals with lactose intolerance is excess gas production and often diarrhoea.

Milk products are nearly ever-present in western diets.

They are contained in a small amount in almost all recipes, restaurant dishes, and processed food.

People with lactose intolerance need to be careful reading food ingredient labels if they wish to avoid consuming lactose.

Lactose intolerance is not all or nothing condition. The amount of lactose that can be tolerated varies from person to person, and decreases with age. Dietary control of lactose intolerance depends on people learning through trial and error how much lactose they can handle.

People with irritable bowel syndrome or Crohn's disease have a reduced level of the lactase enzyme.

About 90 percent of Asians are lactose intolerant; the number reduces to about 70 percent of African-Americans and Native Americans. The majority of Europeans have the mutation rendering them lactose-tolerant with only up to 20 percent exhibiting symptoms. Lactose intolerance is therefore widely regarded as a medical condition in Europe and North America.

Certain antibiotics can cause temporary lactose intolerance by interfering with the intestine's ability to produce the lactase enzyme.

Analysis of Lactose Intolerance and Symptoms

People with this condition experience symptoms as early as 30 minutes or up to several hours after consuming foods or drinks containing lactose.

Without lactase, the lactose in milk remains uncleaved and unabsorbed. Lactose cannot pass easily through the intestinal wall into the bloodstream. It therefore remains in the intestines.

Thereafter, gut bacteria adapt to the abundance of lactose (relative to other sugars like glucose) and switch over to metabolising lactose. This leads to production of copious amounts of gas by fermentation.

The gas causes unpleasant abdominal symptoms such as:

  • Stomach cramps
  • Bloating
  • Flatulence
  • Diarrhoea
  • Nausea

    Like other unabsorbed sugars, e.g. mannitol, the lactose raises the osmotic pressure of the colon contents, preventing the colon from reabsorbing water and hence causing a laxative effect to add to the excessive gas production.

    Severity varies, depending on how intolerant a person is. You may react to just a few sips of milk. Others may be able to handle several servings. The condition is not considered serious, but it can be distressing.

    In rare cases, children are born without the ability to produce lactase. For most people, however, lactase deficiency is a condition that develops naturally over time.

    After about the age of 2 years, the body begins to produce less lactase. Nevertheless, many people may not experience symptoms until they are much older.

    Diagnosis of Lactose Intolerance

    Some patients with symptoms of irritable bowel syndrome in fact have lactose intolerance without knowing it.

    A simple diagnosis can clarify the issue. After an overnight fast, 50 grams of lactose in a solution with water is swallowed. If the lactose cannot be digested, enteric bacteria will metabolise it and produce hydrogen.

    This can be detected in the air the patient exhales. The test takes about 2 to 3 hours.

    A medical condition with similar symptoms is fructose malabsorption. Although not as precise a test, an estimate of lactose intolerance can be made.

    Drink two cups of milk on an empty stomach and watch for signs of intestinal discomfort over the next several hours.

    The following day, eat two ounces of hard cheese or drink two cups of lactose-free milk. If symptoms are experienced only on the first day, the individual may be lactose intolerant.

    If symptoms are experienced on both days, the individual may have an allergy to dairy products, which is unrelated to lactose intolerance.

    Some individuals are able to self-diagnose without intentionally testing themselves, simply by realizing that their symptoms always correspond to prior lactose consumption.

    Treatment of Lactose Intolerance

    There is no treatment that can improve the body's ability to produce lactase. However, symptoms can be controlled through diet.

    One solution is avoiding milk. Another solution is using lactose-free milk. This is produced by passing milk over lactase enzyme bound to an inert carrier. Once the molecule is cleaved, there are no lactose ill effects, whatever the milk drinker's ancestry.

    Alternatively, a harmless bacterium such as L. acidophilus may be added. This affects the lactose in milk the same way it affects the lactose in yoghurt.

    Another recent solution has been lactase pills that provide the missing enzyme, allowing a person to tolerate milk products for about 30-45 minutes after taking a pill.

    Lactase enzyme is also available as a liquid. Adding a few drops of the enzyme will convert the lactose in milk or cream, making it more digestible for people with lactose intolerance.

    Lactose-reduced milk and other products are available at most supermarkets. The milk contains all of the nutrients found in regular milk and remains fresh for about the same length of time, or longer if it is super-pasteurised.


    Many people are more tolerant of yoghurt than milk because it contains lactase produced by the bacterial cultures used to make the yoghurt. In addition, hard cheeses such as Swiss cheese produce far less reaction than the equivalent amount of milk because the cheese making and aging processes greatly reduce the amount of lactose.

    A typical Swiss or Cheddar might contain 5% of the lactose found in whole milk. Long-aged cheeses contain almost no lactose at all.

    There has been an increase in the number of lactose-reduced and lactose-free dairy products. These products include cottage cheese, American cheese and ice cream.

    Such products are made using milk substitutes such as soymilk, almond milk, or rice milk.

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