How eating dirt may be good medicine
Geophagia, or the eating of dirt, is an ancient habit, dating back to 1800BC or further. According to an account in the 30 November issue of Nature, there are records of it from Sumeria, Egypt and China, but it has received little attention from the anthropology researchers.
At least two millennia ago, markets in Greece were selling terra sigillata,
which was clay moulded into coin shapes and claimed to possess medicinal
properties.
One school of thought maintains that clay provides essential minerals
to the diet. This belief has some basis, bearing in mind that natural
clays consist of silicon dioxide and aluminium oxide, together with calcium,
iron and zinc and trace elements.
Research in the University of Toronto in the 1990s examined clays that
people had eaten at the end of the century. They were consumed in China
during famines, in North Carolina for general health and in Zimbabwe
to control diarrhoea. The trace minerals derived from them offered a
good supplement to a poor diet. However, clay may not only provide trace
elements but may leach them from the digestive tract. Laboratory studies
have shown that in the milieu nutrients incubated with clays and simulated
gastric juices may bind firmly to the lattice of a clay, removing iron,
zinc and copper.
In Tanzania some women believed that eating dirt from their walls caused
anaemia, while others that it overcame it.
There have been indications that zinc deficiency may induce geophagia.
Lack of zinc leads to loss of taste and this makes dirt more acceptable.
In turn this reinforces geophagia, which releases more zinc and continues
the cycle. In reducing the possible intake of toxic substances in the
environment, geophagia may play an important role.
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Pharmaceutical Journal
Bats have long had a reputation for their marvellous sense of location. They have also been reputed for their blindness. Indeed, the 18th century
poet,
William Collins, was understating the case when he wrote, “Now air is
hush’d, save where the weak-ey’d bat with short shrill shriek flits
by on leathern wing”. And the proverbial expression “bats in the
belfry” suggests that these creatures may make limited excursions into
the wider world.