Lactose Intolerance

Medically Reviewed By William C. Lloyd III, MD, FACS

What is lactose intolerance?

Lactose intolerance, or “lactase deficiency,” is a condition that causes discomfort in the upper abdomen, resulting in bloating, gas and diarrhea. Lactose intolerance is the result of a deficiency in an enzyme (lactase) that breaks down the sugar known as lactose that is found in milk. Although low lactase levels are fairly common, not everyone with low amounts of the enzyme is lactose intolerant. Lactose intolerance most often occurs during or right after eating dairy products.

Intolerance to lactose is a common digestive problem in the United States. Varying degrees of lactose intolerance are common among adults. The disorder is more common in individuals of Asian, African, Native American, or Mediterranean ethnicity compared to those of Northern and Western European descent (Source: NDDIC).

Lactose intolerance typically develops in people over a period of time. Most commonly, people begin to experience symptoms of lactose intolerance later in childhood and onward, when the body begins to produce lower levels of lactase. For this reason, children younger than 6 years do not commonly show signs of lactose intolerance. Adolescents and adults are more likely to show signs of the disease.

If you are suffering from lactose intolerance, you will see signs and symptoms after consuming foods that contain dairy products. The manifestations of lactose intolerance vary among individuals. Some people with lactose intolerance have no symptoms at all, while others may have severe abdominal bloating, pain and diarrhea. Fortunately, lactose intolerance can be treated successfully with over the counter medications containing enzymes to break down lactose. Even better, you can reduce your symptoms of lactose intolerance by slowly adding dairy products into your diet to give your body time to build up its own lactase. Further, because dairy products contain important dietary elements, such as calcium, supplementation of calcium ensures that adequate levels are consumed.

Seek prompt medical care if you are being treated for lactose intolerance but mild symptoms recur or are persistent. In some cases, lactose intolerance can lead to low calcium intake, which can be a serious condition that should be evaluated immediately. Seek prompt medical care if you, or someone you are with, have easily fractured bones, muscle cramps, tooth decay, or unintentional weight loss.

What are the symptoms of lactose intolerance?

Lactose intolerance is caused by the inability to digest the sugar called lactose. This may result in a number of symptoms. The symptoms can vary in intensity among individuals.

Common symptoms of lactose intolerance

You may experience lactose intolerance symptoms following consumption of dairy products. At times any of these digestive symptoms can be severe:

Symptoms that might indicate a serious condition

In some cases, lactose intolerance can lead to low calcium intake, which can be a serious condition that should be evaluated immediately. Seek prompt medical care if you, or someone you are with, have any of these serious symptoms including:

  • Abdominal swelling, distension or bloating
  • High fever (higher than 101 degrees Fahrenheit)
  • Severe abdominal pain
  • Unintentional weight loss

What causes lactose intolerance?

Lactose intolerance is caused by inadequate levels of an enzyme (lactase) present in the small intestine that breaks down the sugar known as lactose that is found in milk. There is some evidence that lactose intolerance may run in families.

Several factors are associated with developing secondary lactose intolerance, including small intestine injury or disease, such as bowel surgery or Crohn’s disease. Infection of the small intestine may cause damage to the lining of the intestinal wall and is a potential cause of lactose intolerance, particularly in children.

What are the risk factors for lactose intolerance?

A number of factors increase the risk of developing lactose intolerance. Not all people with risk factors will get lactose intolerance. Risk factors for lactose intolerance include:

  • Age (risk increases with age)
  • Diseases of the small intestine
  • Ethnicity (higher risk in Africans, Asians, Hispanics, and American Indians)
  • Injury to small intestine (radiation to the abdomen)
  • Premature birth (lactase develops late in third trimester)

You may be able to lower your risk of lactose intolerance by identifying and avoiding the following ingredients in foods that contain lactose:

  • Curds
  • Dry milk solids
  • Milk
  • Milk byproducts
  • Nonfat dry milk powder
  • Whey

How is lactose intolerance treated?

Treatment for lactose intolerance begins with seeking medical care from your health care provider. To determine whether you have lactose intolerance your health care provider will ask you questions and possibly ask you to undergo diagnostic testing.

While the amount of lactase that the body produces is not modifiable, dietary changes can alter the amount of lactose consumed and how the body reacts to lactose when it is consumed. Gradual introduction of foods that contain lactose can give the body the opportunity to adapt to lactose with fewer symptoms.

For people that cannot tolerate lactose, there are many lactose-free and lactose-reduced products on the market. Yogurts and hard cheeses are milk products that possess lower levels of lactose and may be tolerated in some people with lactose intolerance. Affected individuals need to identify dietary substitutions of alternate nutrient sources to maintain energy and protein intake. In addition, enzymes can be given (in the form of pills or liquid) prior to eating milk or milk products to help in the breakdown of lactose and reduce symptoms. Calcium supplementation may be needed to replace dietary calcium and prevent calcium deficiency from a diet that is reduced in milk and milk products.

What are the potential complications of lactose intolerance?

Most often lactose intolerance does not lead to complications. However, it can affect quality of life by limiting the foods you can eat. This may result in unintentional calcium and vitamin D deficiencies or weight loss due to limited food group choices. You can help minimize your risk of serious complications by following the treatment plan your health care professional specifically designs for you. Complications of lactose intolerance include:

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  1. Lactose intolerance. National Digestive Diseases Information Clearinghouse (NDDIC).
  2. Lactose intolerance. PubMed Health, a service of the NLM from the NIH.
  3. Shaukat A, Levitt MD, Taylor BC, et al. Systematic review: Effective management strategies for lactose intolerance. Ann Intern Med 2010. 152: 797-803.
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 13
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