Frequency of Lactose Intolerance within Population Groups
Table 1.1 Frequency of Adult Lactose Intolerance within Population Groups [7]
Global distribution of lactose intolerance.
Population Group Percent
United States Whites 2-19
Finnish 18
Swiss 12
Swedish 4
United States Blacks 70-77
Ibos 99
Bantu 90
Fulani 22
Tutsi 7
Thais 99
Asian Americans 95-100
United States Jews 69
Native Australians 85
Native Americans 99Genetic Factors
Lactose intolerance is an autosomal recessive trait. The allele variations differ in the temporal aspect of their expression. The dominant allele is expressed later and, therefore, the phenotype for the dominant allele is the persistence of production of the lactase enzyme. The recessive allele is expressed only early in life and results in lactose intolerance. The gene that codes for the lactase enzyme is located on chromosome 2. This is the case in all populations, but the reguation of the gene varies. The lactase gene has four common haplotypes- A, B, C, and U. The A haplotype is usually found in populations that exhibit lactase persistence. Increased haplotype diversity occurs in populations that exhibit lactose intolerance. The expression of the lactase persistence phenotype gives genetic advantage to members of populations that consume milk. This is why most express the dominant allele in milk consuming populations. While it is still unclear, it is likely that lactase regulation occurs during DNA transcription because there is variation in mRNA levels between lactase persistent and impersistent individuals. [2] Genetic drift probably also played a role in latase gene diversity. The more homogeneous populations are probably as such because of genetic drift, this is why African cultures have more diversity in the haplotypes. Gene flow, mainly due to colonization, is probably the cause of continued frequencies of lactose intolerance and tolerance within populations. Lactose tolerance is rare in a worldwide sense, but it exists in scattered populations that have no contact. As shown by the low levels of lactose intolerance in United States Whites and the Fulani and Tutsi tribes, the genes evolved independently in different populations around the world.
http://en.citizendium.org/wiki/Lactose_intolerance
DragonRouge (2010-02-09), Grasshoppa (2010-02-09)
Thanks for posting this,I just knew I'm lactose intolerant,what a shame!
smartguy (2010-04-04)
The Tutsi herd cattle, don't they? So lactase persistence would be an advantage and the genes could osmose into neighbours. I'm surprised that the Masai haven't put Kenya in the green. I'd have expected more lactase persistence in India as well, but if milk is fermented as in lassi, yoghurt, cheese etc. the lactose (12 carbon sugar) is split into two 6 carbon sugars - glucose & galactose which are then digestible. It's the beta bond (cellulose type) between these that is the problem. Sucrose (glucose & fructose) and maltose (two glucose) have alpha bonds (starch type) which are more easily hydrolysed. As an example cook two bowls of oatmeal - 1 with a pinch of salt and 1 without - the salted one will taste sweeter as the salt hydrolyses the starch into shorter and sweeter polysaccharides
A Korean colleague was lactase persistent, just as well as her parents emigrated to New Zealand, but that might be because Nord-Sinids are close to Mongols who have always herded cattle. They ferment some of the milk into alcoholic kumiss which would also avoid the problem and is more fun than cheese.
Lactose tolerant, which is good since milk is one of the best nutritions out there. I thank my ancestors every day for starting to digest milk.
Milk is one of the best nutritions, especially milk protein (such as whey).
It is true that milk for example can give you stronger acne prevelance, but acne is easy to get rid of (roaccutane) and it is totally worth it seeing the nutritional benefits of milk consumptions, especially if you are active athlete or similar.
True, milk is fantastic and beneficial, you can even look at the physical shape of societies and cultures that encouraged milk and dairy against those who didn't.
Jealousy? Speaking from the perspective of a lactose intolerant (like myself-which I think sucks).