Lactase is an enzyme found within the human body that is utilized to break down milk sugars or disaccharide lactose. Without this enzyme functioning the human body can not break down and properly utilize milk sugars. Lactase is part of the beta galactosidase family of enzymes that are hydrolases by nature.
Biologically human beings produce lactase beginning in their infancy in order to facilitate the ingestion of a mother's milk. Normally the production of lactase would cease after infancy however in the modern era of agriculture milk in many forms is readily available and actively promoted for consumption. This has changed the duration of lactase production in the body to many years past its intended biological cycle in infancy.
The benefits of lactase production by the human body are many. Milk and the sugars they posses are a source of dense nutrition for people of all ages. The ability to digest and utilize this milk nutrition is of great importance as without it milk food sources will actually cause adverse effects to the digestive system of the human body.
Lactase, like many other enzymes, serves as a catalyst within living organisms to facilitate the break down of complex sugars that our bodies can not use such as disaccharides into simple sugars that our bodies can use such as galactose (milk sugar) and glucose (sweet sugar). This lactase reaction occurs within the small intestine along its tissue walls.
The condition of lactose intolerance literally means milk sugar intolerance. This is a condition where a human does not continue to create lactase after infancy and as such can not break down complex milk sugars. The effect of milk sugar introduced into digestive tract of someone with lactose intolerance is that of severe digestive discomfort including symptoms of bloating, stomach pain, and diarrhea. Oddly, the condition of lactose intolerance is not really one of biological disorder as evolutionarily speaking we are only meant to digest milk fats as infants.
For those suffering from lactose intolerance there have been vast research and development in lactose replacement. Currently, lactose supplements may be taken by a person suffering from the condition of lactose intolerance before a meal which contains milk sugars such as ice cream, cheese, or baked goods. These pills introduce lactase into the body from outside sources and begin digesting milk fats before they reach the small intestine and cause discomfort.