From Helen Fullerton
Ammanford, Carmarthen
Niels Skakkebaek’s hypothesis that rising levels of oestrogen-like compounds
in our environment suppress sperm counts should not be expected to account for
all the observations (This Week, 11 May, p 10). If Skakkebaek is right that
sperm counts are going down, selenium deficiency could be another important
factor, and may help account for the geographical distribution and time
variability. It’s well known that selenium deficiency impairs spermatogenesis
and reduces sperm viability.
Selenium soil levels are low in Britain and much of northern Europe.
Consequently, the levels in our bread, milk and meat are inadequate. Our
selenium intake fell from 60 micrograms per day in the late 1970s to 36
micrograms a day in one study in 1994, reflecting a switch in our source of
flour from Canadian selenium-rich wheat to low-selenium homegrown or European
wheat.
Finnish soils are notoriously low in available selenium and the Finns’
mid-1970s intake was 25 micrograms of selenium a day. This was dramatically
changed in 1984 by the Finnish government’s decision that every bag of
fertiliser should supply a certain level of selenium per hectare.
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The levels in cereals, meat and dairy products soared, and human intake rose
to 90 micrograms a day, conferring protection against heart disease. It can be
deduced that adequate dietary selenium may account for the high sperm count
recorded for Finnish men.
Variations in sperm count between states in the US may well reflect the
source of flour and other foods, and also losses in processing. The overall high
sperm count in the years 1976 to 1977 should be examined to see whether they
reflect a continent-wide drought: drought would oxidise selenite to the more
available selenate and increase selenium uptake by the crops.
These considerations should in no way detract from Skakkebaek’s hypothesis.
Selenium deficiency may be a major, minor or contributory cause, depending on
the circumstances.
