Lactose intolerance is the inability of the small bowel to absorb lactose (a form of sugar found in dairy products) due to a deficiency in the enzyme lactase. The unabsorbed lactose travels thought the small bowel and into the colon, where colonic bacteria digest the lactose and produce several malodorous gases. In addition to the gases produced by colonic bacteria, the osmotic load of the undigested lactose in the colon serves to draw water in from the body and this increased water content causes loose, diarrheal stools.
The most significant determinant of one's ability to process lactose is ethnicity. For example, the following are the rates of lactose intolerance in adults of several different ethnicities:
- Caucasian: 7-20% (those of northern European descent have the lowest rates)
- Asian: over 90% of people from east Asia
- Native American: 95%
- African American / Hispanic: 65-75%
As you can see, it is reasonable to determine the likelihood of having true lactose intolerance based on one's ethnicity. Additionally, lactose intolerance can develop following a gastrointestinal infection and is often seen in inflammatory bowel diseases.
Symptoms of lactose intolerance are due to the malabsorption of lactose as described above and include: bloating, crampy abdominal pain
, flatulence, and diarrhea
all in relation to the ingestion of a lactose load.
Lactose intolerance can be diagnosed clinically by a lactose tolerance test in which a patient ingests 50g of lactose and then has successive blood draws to monitor for an increase in blood sugar in relation to the lactose load (little to no increase indicates lactose intolerance). another test is the hydrogen breath test.
Treatment essentially entails avoiding lactose containing products (mild, ice-cream, yogurts, cheeses, etc) or supplementing with lactase preparations that can be taken orally with food (eg Lactaid).
Hope this helps!