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The Times, London,
Sept. 10, 2003
Far
from being normal, the amounts of oestrogen found in women
in Britain and other developed countries are, in historical
terms, highly abnormal. Dr Tessa Pollard, of the University
of Durham, told the British Association for the Advancement
of Science conference in Manchester, north west England, that
it was probably only in the past 50 years that the levels had
increased so much.
Studies in Mali and the Congo had shown that African women
in subsistence economies are exposed to much less oestrogen
during their lifetime than are Western women. Among the Dogon
people of Mali, women typically experience about 110 menstrual
cycles in a lifetime. British women have about 400.
The difference is that Dogon women typically have eight or
nine children and breastfeed them all. Breastfeeding halts
the menstrual cycle and reduces production of oestrogen, so
there are long spells when Dogon women are not exposed to it.
British women have one or two children on average and breastfeed
for shorter periods. In addition, women in rich countries start
their periods sooner and end them later. A good diet and leisure
also increase oestrogen. One in nine women in Britain can expect
to suffer breast cancer.
A study of oestrogen levels in Lese women in the Congo by Gillian
Bentley, of University College London, found that they were
much lower than in women in Boston.
The conclusion is not that the African women are abnormal — they
probably represent the evolutionary norm. High levels of oestrogen
are linked to increased risks of breast cancer, but protect
against heart disease. On the assumption that oestrogen levels
are set by nutritional status in the womb or in infancy, Dr
Pollard says that one would expect Asian women who migrate
to Britain to have lower levels of oestrogen and a lower breast
cancer risk. Statistics show that they do indeed suffer less
breast cancer.
The Statesman
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