While some of
us can drink glasses of
milk and
digest it well, others cannot digest even a single
glass? Scientifically, this is because the former have ability to digest
lactose found in milk while the latter are lactose
intolerant (LI). The undigested
lactose in them results in stomach-ache and diarrhea. People are lactose
intolerant because early in life they have shut off the gene that produces
enzyme called the
lactase, which breaks lactose into two simpler sugars,
glucose and galactose. Lactose intolerance is often genetic and might even
depend upon which region of the world one hails from. For instance, people from
North and Central Europe can digest milk well and are lactase
persistence (LP)
but those from Middle East and South
Africa face difficulty, they being LI. In India, a
study by Dr.R.K.Tandon and others
suggested that People from South India were intolerant while those from New Delhi were not. A
recent 2004 study conducted by Dr.S.V.Rane showed that almost half of India’s
population was Lactose intolerant.
What could be
he reason for such variance in spread of LI-LP when human beings across the
world have about 99.5% genes in common, is a subject that is holding the
attention of researchers. A tentative answer could perhaps emerge from our
genetic and cultural background. Some time back European geneticists claimed
that they have found noticeable difference between dairying communities and
non-pastoral groups with the dairying communities having, by and large, a high
LP prevalence than the others. There is another hypothesis called
cultural-historical model and geneticist Leena Peltonen of UCLA has discovered
a useful marker in the DNA chain close to where the lactase gene is located.
These studies are still continuing and till then we will not know for certain
why some digest milk easily while others can’t.
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