Scientifically speaking, lactose is a sugar molecule called a disaccharide. This means it is composed of two sugar units; one each of galactose and glucose and linked together. Lactose makes up anywhere from two to eight percent of the solids in milk. Although glucose can be used directly by the body, galactose requires conversion to glucose by the liver.
For those so inclined, the empirical formula of lactose is C12H22O11 and its molecular weight is 342.3. Although it has the same empirical formula as sucrose (cane sugar) and maltose (malt sugar), it differs from both in structure.
Lactose is not found in plants, but is the sugar found in milk. When milk sours, lactose is converted by bacteria to lactic acid, making the product easier to digest. Lactose is formed in the mammary glands of all lactating animals. Produced commercially, lactose is a byproduct of milk processing where it is used to enhance flavor, help brown baked goods, and to firm pills when they are compressed.
The problem of lactose intolerance usually begins quite early in life and proceeds to worsen with age. Since the food of all young mammals is milk, they are naturally given an enzyme to help break down this milk sugar. The enzyme lactase is secreted in the intestine so that lactose can be broken down and transported across the cell membranes. When the young no longer need milk as their sole source of nourishment, the enzyme diminishes in its production.
This is where the problem develops. With the diminishing production of the necessary enzyme to break down the sugar molecule, unabsorbed lactose remains in the gut exposured to intestinal bacteria. This exposure causes fermentation which, in turn, produces the gas and pain. Therefore, it appears that milk is not meant for adults!
Lactose intolerance is seen across many ethnic backgrounds. Estimates range from 2% in Northern Europeans to nearly 100% in adult Asians and American Indians. Sixty to eighty percent of Blacks and Ashkenazi Jews and 50-80% percent of Latinos have an intolerance to dairy products.
Lactose intolerance can also be associated with intestinal disorders. Some include irritable bowel syndrome, Crohns disease, or other inflammatory bowel diseases, as well as abdominal injuries or surgeries. Some medications may also contribute to the problem. Whatever the reason, the result is very painful.
- American Family Physician article http://www.aafp.org/afp/20020501/1845.html
- A personal review of lactose intolerance from Eva’s Kitchen Confidence http://www.telusplanet.net/public/ekende/lactose.htm
This page was updated in December 2005.