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Klinisk Biokemi i Norden · 3 2019
relationship was observed between selenium intake
and overall cancer risk after adjusting for age, body
mass index, and smoking.
Thus, selenium appears
to protect against certain cancers at levels somewhat
higher than the average intakes in several European
countries. The protective effect observed in another
meta-analysis appears to be restricted to certain
cancers, i.e. lung, oesophagus, stomach and prostate
cancer, as observed in another meta-analysis (24). In
the NPC trial, conducted in the Eastern area of the
US with lower baseline intake than the states in the
Western US, it was found that supplemental selenium
(200 μg per day as Se-enriched yeast) was associated
with a significantly reduced prostate cancer risk
strykes. The protective effect was mainly confined to
participants with PSA ≤ 4 ng/L and observed particu-
larly in subjects with baseline plasma selenium below
1.34 μmol/L (106 μg/L) that made up the lower tertile
of the cohort (25). In contrast, subjects entering with
plasma levels above about 1.5 μmol/L had no cancer-
protective benefits of supplementation. This finding
accords with no selenium related preventive effect on
prostate cancer in the later SELECT trial (Selenium
and Vitamin E Cancer Prevention Trial) (26). In this
trial supplementation (L-selenomethionine, 200 μg
per day) was given to a population from selenium-
adequate regions of USA, Canada and Puerto Rico
with baseline selenium plasma levels above about
1.4 μmol/L. In this case, it is likely that supplemen-
ted selenomethionine did not further increase the
levels of specific selenoproteins, e.g. selenoprotein P,
that are already optimized at levels above about 1.3
μmol/L. Of further interest are two studies, one from
the US in blacks (27) and one from Sweden (28), both
showing increased lung cancer risk in those with a
premorbide low plasma concentration of selenopro-
tein P in comparison with those with an optimized
level. We may envisage two main categories of pro-
