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Ancient mutation controls lactose intolerance

Researchers in Finland and the US believe they have located the genetic
basis for lactose intolerance.
Up to 50 million Americans, including 75 per cent of African Americans and
90 per cent of Asian Americans suffer from lactose intolerance. This is a
painful digestive condition marked by nausea, cramping, bloating and
diarrhoea when the affected person is exposed the lactose, the natural sugar
in dairy products.

No mutation has ever been found in the gene responsible for lactose
breakdown to account for this condition. But when researchers in Los Angeles
and Finland looked at a region close to, but outside , the gene they found a
mutation in a group of 196 lactose intolerant people living in Finland. They
found it in people of African, Asian and European descent. The fact it's so
widespread across ethnic groups suggests this is an ancient mutation, with
its roots far back in human history. The researchers wonder whether we were
all lactose intolerant at one time, but the emergence of agriculture
favoured the emergence of tolerance.

The study opens up the way to more accurate diagnosis of lactose
intolerance, based upon DNA analysis. Current diagnostic methods are
uncertain and hard to carry out, so a new approach would certainly benefit
those who need to know what is causing their symptoms.


Source
Nature Genetics January 14 2002