What does Dairy do ?

Lactose intolerance, also called lactase deficiency and hypolactasia, is the inability to digest lactose, a sugar found in milk and to a lesser extent milk-derived dairy products. It is not a disorder as such, but a genetically-determined characteristic.

Lactose intolerant individuals have insufficient levels of lactase, an enzyme that catalyzes hydrolysis of lactose into glucose and galactose, in their digestive system. In most cases this causes symptoms which may include abdominal bloating and cramps, flatulence, diarrhea, nausea, borborygmi (rumbling stomach), or vomiting after consuming significant amounts of lactose.

Some studies have produced evidence that milk consumption by lactose intolerant individuals may be a significant cause of inflammatory bowel disease.Most mammals normally cease to produce lactase, becoming lactose intolerant, after weaning, but some human populations have developed lactase persistence, in which lactase production continues into adulthood. It is estimated that 75% of adults worldwide show some decrease in lactase activity during adulthood.

The frequency of decreased lactase activity ranges from 5% in northern Europe through 71% for Sicily to more than 90% in some African and Asian countries. This distribution is now thought to have been caused by recent natural selection favoring lactase-persistent individuals in cultures in which dairy products are available as a food source. While it was first thought that this would mean that populations in Europe, India, and Africa had high frequencies of lactase persistence because of a particular mutation, it was later shown that lactase persistence is caused by several independently occurring mutations.


"Lactose intolerance" primarily refers to a syndrome having one or more symptoms upon the consumption of food substances containing lactose. Individuals may be lactose intolerant to varying degrees, depending on the severity of these symptoms. "Lactose malabsorption" refers to the physiological concomitant of lactase deficiency (i.e., the body does not have sufficient lactase capacity to digest the amount of lactose ingested). A medical condition with similar symptoms is fructose malabsorption. Lactase deficiency has a number of causes and is classified as one of three types:

Primary lactase deficiency is genetic, only affects adults and is caused by the absence of a lactase persistence allele. It is the most common cause of lactose intolerance as a majority of the world's population lacks these alleles.Secondary, acquired, or transient lactase deficiency is caused by an injury to the small intestine, usually during infancy, from acute gastroenteritis, diarrhea, chemotherapy, intestinal parasites or other environmental causes.

Congenital lactase deficiency is a very rare, autosomal recessive genetic disorder that prevents lactase expression from birth.It is particularly common in Finland. People with congenital lactase deficiency cannot digest lactose from birth, and therefore cannot digest breast milk.

Lactose intolerance is not an allergy because it is not an immune response, but rather a problem with digestion caused by lactase deficiency. Milk allergy is a separate condition, with distinct symptoms that occur when the presence of milk proteins trigger an immune reaction.

Dairy and IBS?

Another common suspect for IBS sufferers is dairy. Whilst initially dairy can be moderate on the stomach, the problems lie with the inability for many to break down the sugars in dairy, most commonly lactose.

We look at the actual reasons for dairy intolerance and the examine the options to deal with it.   The following comes from Wikipedia, which gives a great overview of the basic science behind dairy intolerance.

This particular piece deals with lactose in particular, however digetsive disorders may vary with other dairy produce.   However this piece looks at the most common digestive issue with dairy.


Lactose intolerance is a consequence of lactase deficiency, which may be genetic or environmentally induced. In either case, symptoms are caused by insufficient levels of the enzyme lactase in the lining of the duodenum. Lactose, a disaccharide molecule found in milk and dairy products, cannot be directly absorbed through the wall of the small intestine into the bloodstream so, in the absence of lactase, passes intact into the colon. Bacteria in the colon can metabolise lactose, and the resulting fermentation produces copious amounts of gas (a mixture of hydrogen, carbon dioxide and methane) that causes the various abdominal symptoms. The unabsorbed sugars and fermentation products also raise the osmotic pressure of the colon, causing an increased flow of water into the bowels (diarrhea).[19] Certain mutation in the LCT gene allow lactase continue to be expressed after stopping breast feeding. The LCT gene which encodes the lactase protein is located on the long arm (q) of chromosome 2 in region 21. The locus can be expressed as 2q21.


To assess lactose intolerance, intestinal function is challenged by ingesting more dairy products than can be readily digested. Clinical symptoms typically appear within 30 minutes, but may take up to two hours, depending on other foods and activities.[20] Substantial variability in response (symptoms of nausea, cramping, bloating, diarrhea, and flatulence) is to be expected, as the extent and severity of lactose intolerance varies among individuals.

Lactose intolerance is distinct from milk allergy, an abnormal immune response, (usually) to milk proteins. They may be distinguished in diagnosis by giving lactose-free milk, producing no symptoms in the case of lactose intolerance, but the same reaction as to normal milk in the presence of a milk allergy. An intermediate result might suggest that the person has both conditions. However, since lactose intolerance is common (some degree of it being found in most adults worldwide), it is not considered a disease and a medical diagnosis is not normally required. If positive confirmation is necessary, four tests are available.