FW: Gene Variation Found for Lactose Intolerance

[Guest guest]

[Factual article relevant to previous difference of opinon on this list.]

 

" The researchers speculate that, initially, human adults were unable to

digest lactose. A gene variation allowed some people to consume milk

products in adulthood, but those who are lactose intolerant carry the

original variant. "

 

http://dailynews./h/nm/20020114/hl/lactose_1.html

 

 

Gene Variation Found for Lactose Intolerance

 

By Keith Mulvihill

 

NEW YORK (Reuters Health) - Scientists have identified a genetic variation

that explains why some people are unable to digest milk products, a

condition known as lactose intolerance.

 

While less common in those of European descent, lactose intolerance affects

30 to 50 million North Americans, including 75% of African Americans and

90% of Asian Americans.

 

The new findings will hopefully pave the way towards a simpler diagnostic

DNA test that can be performed from blood samples to identify those who are

lactose intolerant, explained lead investigator Dr. Leena Peltonen of the

University of California, Los Angeles.

 

``The tests currently available are either unreliable or very

complicated,'' she told Reuters Health. Symptoms of the problem, which can

occur within 30 minutes and 2 hours of ingesting lactose--the sugar found

in milk--are usually mild, and include cramps, bloating and diarrhea.

 

The team of researchers evaluated the DNA of 196 lactose-intolerant Finnish

men and women, 9 Italians, 9 Germans and 22 South Koreans. They also tested

blood more than 900 anonymous donors from Finland and from 109 people from

the United States and France. The findings appear in the advance online

publication of the February issue of the journal Nature Genetics.

 

The investigators looked at the gene for lactase-phlorizin hydrolase, an

enzyme produced by cells in the intestine to break down lactose. The enzyme

is active in infants but declines after weaning in many people.

 

According to the analysis, there were no variations in the gene for

lactase-phlorizin associated with lactose intolerance. However, the

researchers did find a region outside the gene that was associated with the

disorder. What's more, the gene variant was associated with lactose

intolerance, regardless of the individual's ethnic background.

 

``The same mutation is found in many different populations and thus is must

be very old,'' Peltonen told Reuters Health.

 

The mutation that allowed individuals to consume milk into adulthood may

have conferred a survival advantage and thus became more common in

populations that had domesticated cows and goats.

 

``Actually this mutant form of the gene is the ancient, original form of

the gene which became mutated thousands of years ago when humans started

the dairy culture and the lactose tolerance gene got spread among the human

population,'' she said.

 

The researchers speculate that, initially, human adults were unable to

digest lactose. A gene variation allowed some people to consume milk

products in adulthood, but those who are lactose intolerant carry the

original variant.