Overview
People with lactose intolerance cannot digest lactose, a sugar found in milk and dairy products. Individuals with lactose intolerance typically suffer from stomach bloating, nausea, stomach pain, and diarrhea after consuming milk or dairy products. Although this condition is harmless, its symptoms can cause much discomfort to people with lactose intolerance.
Digestion of lactose in the digestive system
When we eat food, enzymes found within our digestive system break the nutrients from the food down into smaller molecules that can be absorbed. These smaller molecules will pass through the intestinal wall and subsequently go into the bloodstream. The small intestine, an organ that connects the stomach and large intestine, is the organ where most of the nutrients, including the breakdown products of lactose, are absorbed.
In people with lactose intolerance, the lactose molecules will pass through the small intestine undigested and then enter the large intestine. The presence of lactose in the large intestine will lead to the release of more fluid in this organ in order to facilitate the passing of lactose. This will result in diarrhea for the affected individuals. Bacteria present in the large intestine can metabolize lactose molecules, producing gas. Gas production is another symptom of lactose intolerance.
In humans, lactose is digested by the enzyme lactase. This enzyme is produced by cells that line the walls of the small intestine. Most individuals produce lactase as infants, and this assists with the breakdown of lactose present in breast milk. In most cases, the cells of the small intestine make less of this enzyme as people grow older. If the level of lactase is too low in an individual, most of the lactose consumed will not be digested, resulting in lactose intolerance.
Causes of lactose intolerance
As mentioned in the previous paragraph, lactose intolerance is caused by low levels of lactase in the small intestine of the affected people. There are four types of lactose intolerance:
Primary lactose intolerance. This is the most common type of lactose intolerance. Persons who develop this type of lactose intolerance initially produce enough lactase as babies. When they reach adulthood, the production of lactase drops considerably, making it hard to digest lactose.
Secondary lactose intolerance. This type of lactose intolerance arises when lactase production is reduced in the small intestine following surgery, injury, or a disease. Treating the disease might restore the levels of lactase, leading to an improvement in symptoms.
Congenital lactase intolerance. Individuals who are born with this rare form of lactose intolerance cannot make lactase in their small intestines. This deficiency is due to genetics. These individuals have inherited two copies of the variants of the lactase gene, one from each parent. The variant or mutant form of the lactase gene is defective, resulting in the inability to produce lactase.
Developmental lactose intolerance. Babies who are prematurely born may suffer from this type of lactose intolerance. Their small intestines are not fully developed and the levels of lactase made are insufficient.
Symptoms of lactose intolerance
Those suffering from lactose intolerance show symptoms from thirty minutes to two hours after eating food or having drinks containing lactose. Common symptoms include:
· Abdominal pain and cramps
· Nausea
· Diarrhea
· Stomach bloating
· Gas
Adapted from Cleveland Clinic (my.clevelandclinic.org)
Diagnosis
In the clinic, healthcare professionals can carry out a number of diagnostic tests to confirm if an individual has lactose intolerance. These tests are described below.
Hydrogen breath test. In this test, an individual tested will be asked to drink a liquid containing lactose. The amount of hydrogen and methane gases in the person’s breath will be measured at regular intervals. High levels of these gases will indicate that the person is lactose intolerant. When a person is lactose intolerant, lactose present in food or drink will enter the large intestine of the digestive system. Here, the bacteria in this organ will ferment the lactose and produce hydrogen and methane gases, which can be detected in the breath of the affected person.
Blood sugar test. This test determines if one’s digestive system absorbs lactose. The individual subjected to this test fasts for eight hours prior to testing. The individual then consumes a drink containing lactose. Blood samples will be taken from the individual and tested for the levels of glucose. If lactase is present in the small intestine, lactose will be broken down into sugars such as glucose, which will be absorbed by the small intestine and enter the bloodstream. Thus, this will lead to a rise in the levels of glucose in the blood. If the blood sugar levels do not increase, the individual tested will be considered lactose intolerant.
Stool acidity test. This test is applied to infants and small children. A child is fed food or drink containing lactose. A stool sample is obtained from the child and examined for lactic acid, glucose, and other byproducts. The presence of these analytes suggests that the individual tested is lactose intolerant.
Management
Currently, there are no treatments that can induce the production of lactase in the small intestines of people affected by lactose intolerance. However, the unpleasant symptoms experienced can be avoided with careful management of one’s diet.
Typically, an individual with lactose intolerance will avoid food or drinks containing lactose such as milk and dairy products. However, there are several ways that a person with lactose intolerance can still consume dairy products and minimize the symptoms associated with the condition. These alternative ways are as follows:
Lactose-free or lactose-reduced dairy products. People with lactose intolerance can eat or drink lactose-free dairy products.
Adding lactase supplements to milk and lactose-containing dairy products. Lactase supplements can be taken in the form of pills. These pills should be taken before a meal. Lactase supplements in the form of liquid can be added to lactose-containing drinks before these drinks are consumed.
Consuming small amounts of lactose-containing dairy products as part of regular meals. Mayo Clinic has suggested drinking lactose-containing dairy products such as milk during regular meals. The digestive process will be slowed down and the severity of the lactose intolerance symptoms will be reduced.
References
Assessed and Endorsed by the MedReport Medical Review Board