Selenium references – a selection
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Immune system
The function of the immune system is closely related
to the interactions between free radicals and antioxidants.
A sufficiently high concentration of antioxidants
in the body seems important for fighting infections
[A-863, A-3695].
Deficiency of selenium is accompanied by a decrease
of the immune function [A-826], while supplementation
with selenium has marked immunostimulatory effects
[A-7350]. In an animal trial, supplementation with
selenium was able to restore age-related immune decline
[A-7351].
The result of a controlled study of selenium supplementation
to patients with severe inflammatory response syndrome
caused by infection was improved clinical outcome
and reduction of the incidence of acute renal failure
[A-5991]. In the most critically ill patients, there
was a significantly lower mortality in the group
supplemented with selenium. In a study of 725 institutionalised
elderly persons, supplementation with 100 ?g selenium
and 20 mg zinc improved immunity significantly compared
with placebo [A-5471].
Cancer
Epidemiological studies have shown a correlation
between high selenium status and lower risk of
certain forms of cancer, eg. bladder cancer [A-7259]
and prostate cancer [A-7167], and high dietary
selenium intake or high selenium status is associated
with lower cancer mortality in general [A-6218].
Biochemical studies [A-6753] and other studies
have demonstrated promising possibilities for the
use of selenium alone or in combination with other
antioxidants for the primary prevention ("chemoprevention")
of cancer [A-6238] or prevention of recurrence
after surgery [A-5176]. Certain selenoproteins
seem to play a protective role in development of
breast cancer, and possession
of a certain genotype that requires elevated levels
of selenium to retain the basal level of protection
is implicated in some cases [A-6947]. Five well controlled,
double-blind trials have confirmed a positive effect
of selenium supplementation (alone or used with other
substances) on cancer
forms.
In former skin cancer patients who received 200 ?g selenium daily for a period of 4.5 years, a significant reduction of total cancer mortality, of the incidence of lung cancer, prostate cancer, and colorectal cancer was seen [A-3676]. In a more recent report including results from two additional years, the reductions were maintained, however, only prostate cancer remained significantly reduced [A-6901, A-6885]. A slight increase in nonmelanoma skin cancer was found in men with a high baseline plasma level of selenium, although this result hovered at the margin of statistical significance and is inconsistent with findings from other experiments [A-6885]. In certain areas of China the prevalence of hepatic carcinoma (HC) is high due to a large hepatitis B infection rate. In a placebo controlled study of 226 hepatitis B antigen carriers supplemented daily with 200 ?g of selenium yeast or placebo no case of HC occured in the selenium group over 4 years, while seven individuals in the placebo group developed HC. Fortification of table salt with selenium among 130.000 chinese people at risk from five townships lowered the incidence of HC by 35% after six years [A-7140]. Similarly, in a controlled study in 18000 persons from a high-risk area for liver cancer, selenium supplementation was able to decrease the incidence of new liver cancers significantly [A-7292]. In a large placebo-controlled study involving 29584 persons, some supplemented with selenium, beta-carotene and vitamin E, a significant lowering of stomach cancer was found [A-1847]. One of the largest and most recent placebo-controlled studies among Europeans using a dose of antioxidants, including selenium and zinc, found a signicficant 31% reduction of cancer incidence in men, but not in women [A-7267].
Viral infections
Studies have shown that a deficiency of selenium
may aggravate the effects of viral infections,
like influenza [A-6446] and HIV [A-4500, A-4506],
and may even play a role in infections with hemorrhagic
fever viruses, like Ebola [A-7349].
If a normally harmless virus like the coxsackie virus
infects a selenium deficient host, it can mutate
into a virulent form, causing myocarditis [A-7184].
Similarly, Se-deficient mice infected with a mild
influenza virus developed much more severe and prolonged
lung inflammation than Se-adequate mice [A-6446].
HIV infected patients with a selenium deficiency
are also about 20 times more likely
to die from HIV-related causes than those with adequate
selenium levels [A-4500]. It has even been suggested
that ensuring an adequate intake of selenium may
reduce the likelihood of an exposed person being
infected by HIV [A-6431]. Selenium deficiency is
in this context defined as a plasma level below ?
85 ?g/l, a level not attained in many northern European
countries [A-6710].
Cardiovascular disease
It is documented that low selenium status is inversely
associated with platelet aggregation and increased
risk for cardiovascular disease in men with coronary
artery disease [A-4414]. In a cohort of 3387 middle-aged
Danish men, a selenium level below 79 ?g/l was
associated with a significantly increased risk
of ischaemic heart disease [A-1461]. Keshan disease
is a cardiomyopathy seen in persons infected with
coxsackie virus and with extremely low selenium
status [A-6200]. A low blood level of selenium
has also been associated with acute myocardial
infarction [A-328].
In a controlled trial, administration with selenium
and coenzyme Q10 to patients admitted with acute
myocardial infarction improved biochemical parameters,
the functioning of the heart, and seemed to affect
survival positively after one year [A-2398].
Fertility and pregnancy
Researchers have identified a selenoprotein that
helps to rid developing sperm cells of dangerous
radical molecules and also functions as a part
of the structural base of mature sperm [A-5710].
A trial conducted in Scotland in which 69 infertile
men received selenium supplements combined with
small amounts of vitamins did not shown any effect
on the number of sperm cells, but the men who received
the seleniumgroup in this trial were found to have
significantly higher sperm cell motility. In the
selenium group 11% acheived paternity compared
with none in the placebo group. [A-5630].
In another controlled trial supplementation with
selenium and vitamin E decreased semen oxidative
load and increased sperm cell motility [A-6853].
Low intake of selenium also seems to be associated
with a greater risk of preeclampsia [A-7025].
Mood
There are indications that selenium is important
to the function of the brain. In human studies,
low selenium was associated with depression, anxiety,
confusion and hostility [A-6710]. High selenium
diets or supplementation with selenium, on the
other hand, have been able to improve clearheaded-confused
scores and significantly decrease anxiety and tiredness
in younger persons [A-6710]. A controlled study
in elderly, healthy persons did not show this effect
[A-7509], but selenium supplementation improved
mood in a controlled trial with younger subjects
[A-3072].