Lactose intolerance overview: Difference between revisions
No edit summary |
|||
| Line 10: | Line 10: | ||
==Classification== | ==Classification== | ||
There are three major types of lactose intolerance<ref name="Melvin"> [http://aappolicy.aappublications.org/cgi/content/full/pediatrics;118/3/1279|Melvin B. Heyman. ''Lactose Intolerance in Infants, Children, and Adolescents''. PEDIATRICS Vol. 118 No. 3 September 2006, pp. 1279-1286 (doi:10.1542/peds.2006-1721)]</ref> | There are three major types of lactose intolerance:<ref name="Melvin"> [http://aappolicy.aappublications.org/cgi/content/full/pediatrics;118/3/1279|Melvin B. Heyman. ''Lactose Intolerance in Infants, Children, and Adolescents''. PEDIATRICS Vol. 118 No. 3 September 2006, pp. 1279-1286 (doi:10.1542/peds.2006-1721)]</ref> | ||
#Primary lactose intolerance. Environmentally induced by weaning in non dairy consuming societies | #Primary lactose intolerance. Environmentally induced by weaning in non dairy consuming societies. In most Asian and African cultures, mother's milk is the only commonly available milk and so milk consumption beyond infancy is not commonplace, therefore children become weaned, which is the same weaning process for all mammals (domesticated and wild). However societies such as the japanese where milk consumption has been on the increase, demonstrate that notwithstanding the genetic predisposition to lactose intolerance, they now present lower prevalence of lactose intolerance.<ref name="Yoshida">[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1234085&dopt=Abstract ''Studies on the etiology of milk intolerance in Japanese adults'', Yoshida Y, Sasaki G, Goto S, Yanagiya S, Takashina K, Gastroenterol Jpn.;10(1):29–34, 1975]</ref> For any given individual the degree of weaning is probably genetically influenced. | ||
#Secondary lactose intolerance. Environmentally induced, resulting from certain [[gastrointestinal diseases]], including exposure to [[intestinal parasites]] such as [[giardia]]<ref> [http://www.tulane.edu/~wiser/protozoology/notes/intes.html "Intestinal Protozoa" Mark Wiser 2000] </ref><ref>[http://www.emedicine.com/emerg/topic215.htm "Giardiasis" Andre Pennardt February 22, 2006] </ref> | #Secondary lactose intolerance. Environmentally induced, resulting from certain [[gastrointestinal diseases]], including exposure to [[intestinal parasites]] such as [[giardia]].<ref> [http://www.tulane.edu/~wiser/protozoology/notes/intes.html "Intestinal Protozoa" Mark Wiser 2000] </ref><ref>[http://www.emedicine.com/emerg/topic215.htm "Giardiasis" Andre Pennardt February 22, 2006] </ref> In such cases the production of lactase may be permanently disrupted.[http://www.aafp.org/afp/20020501/1845.html] + (Wiser 2000, Pennardt 2006). | ||
#Congenital lactase deficiency present at birth and diagnosed in early infancy. | #Congenital lactase deficiency present at birth and diagnosed in early infancy. | ||
Revision as of 19:39, 25 March 2013
|
Lactose Intolerance Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Lactose intolerance overview On the Web |
|
American Roentgen Ray Society Images of Lactose intolerance overview |
|
Risk calculators and risk factors for Lactose intolerance overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Lactose intolerance is the term used to describe a decline in the level of lactase, an enzyme needed for proper metabolization of lactose (a sugar that is a constituent of milk and other dairy products), in human beings.
Epidemiology and Demographics
An estimated 70%[1] of adult humans are considered lactose intolerant, it is uncommon in healthy northern westerners and a few others groups.
Classification
There are three major types of lactose intolerance:[2]
- Primary lactose intolerance. Environmentally induced by weaning in non dairy consuming societies. In most Asian and African cultures, mother's milk is the only commonly available milk and so milk consumption beyond infancy is not commonplace, therefore children become weaned, which is the same weaning process for all mammals (domesticated and wild). However societies such as the japanese where milk consumption has been on the increase, demonstrate that notwithstanding the genetic predisposition to lactose intolerance, they now present lower prevalence of lactose intolerance.[3] For any given individual the degree of weaning is probably genetically influenced.
- Secondary lactose intolerance. Environmentally induced, resulting from certain gastrointestinal diseases, including exposure to intestinal parasites such as giardia.[4][5] In such cases the production of lactase may be permanently disrupted.[2] + (Wiser 2000, Pennardt 2006).
- Congenital lactase deficiency present at birth and diagnosed in early infancy.
Without lactase, the lactose disaccharide in many dairy products remains uncleaved and can not be absorbed through the intestinal wall into the bloodstream, so remains in the intestines. Enteral bacteria adapt to the relative abundance of this undigested sugar and their operons quickly switch over to lactose metabolism, which produces copious amounts of gas by fermentation.
This also causes a range of unpleasant abdominal symptoms, including stomach cramps, bloating, flatulence and diarrhea. As with other unabsorbed sugars (mannitol), the lactose raises the osmotic pressure of the colon contents, preventing the colon from reabsorbing water and hence causing a laxative effect to add to the excessive gas production.
References
- ↑ Kretchmer N. Lactose and lactase: a historical perspective. Gastroenterology, 1971;61, 805–813
- ↑ B. Heyman. Lactose Intolerance in Infants, Children, and Adolescents. PEDIATRICS Vol. 118 No. 3 September 2006, pp. 1279-1286 (doi:10.1542/peds.2006-1721)
- ↑ Studies on the etiology of milk intolerance in Japanese adults, Yoshida Y, Sasaki G, Goto S, Yanagiya S, Takashina K, Gastroenterol Jpn.;10(1):29–34, 1975
- ↑ "Intestinal Protozoa" Mark Wiser 2000
- ↑ "Giardiasis" Andre Pennardt February 22, 2006