findings is unclear. Because most of plasma
copper is bound to ceruloplasmin, an increase in
copper may be required for increased antioxi-
dant capacity in response to muscle damage
(Dressendorfer et al. 1982; Anderson & Guttman
1988; Aruoma et al.1988). Apparently, exercise
results in a redistribution of copper, but how this
occurs is not known, nor is how this might affect
adaptation to training.
Copper status and performance
Little data exist regarding the effects of copper
status and performance. Lukaski et al. (1996)
reported that nutritional status and dietary
intake of several micronutrients including
copper were useful predictors of 100-yard (91-m)
freestyle swimming performance in collegiate
male swimmers. However, no significant correla-
tion between V
.
o2max.and plasma copper levels in
trained athletes or untrained subjects was found
(Lukaskiet al. 1983). No studies have examined
the effect of copper supplementation on perfor-
mance. Although copper can be lost in sweat
(Gutteridgeet al. 1985), it is not likely that exer-
cise and training will lead to a deficiency.
Summary
Most athletes appear to have adequate copper
status. There is concern that some athletes,
especially females, are not ingesting sufficient
amounts of copper in their diet, but whether the
body adapts to slightly smaller dietary amounts
than the ESADDI needs to be determined.
Results from studies examining changes in blood
copper levels after acute and chronic exercise are
equivocal. After acute exercise, there appears to
be a transient redistribution of copper among
body compartments leading to copper changes
in the blood, but how this occurs is not known
and requires further study (Marrella et al. 1993).
Studies are needed to assess how copper status,
the type of exercise and training, and the dura-
tion and intensity of exercise affect acute and
chronic changes in blood copper levels. There is
no basis to recommend copper supplementation
for athletes, rather athletes should ingest foods
rich in copper. It should be noted that high
amounts of vitamin C and high levels of dietary
zinc can reduce the absorption of copper and
may lead to reduced copper status (Reeves 1997).
On the other hand, iron supplements do not
affect blood copper levels (Newhouse et al. 1993).Selenium
Selenium has received recent attention in the
media because of an interesting randomized con-
trolled trial where it was found that 200mg sele-
nium · day–1 for about 4 years resulted in a
significant reduction in total cancer mortality
and incidence of lung, colorectal and prostate
cancers (Clark et al. 1996). Before selenium sup-
plements are recommended, further studies
are needed to confirm these findings and evalu-
ate circumstances where selenium may have
adverse effects (Colditz 1996). The reason that
selenium may exert this positive effect on
cancer occurrence is likely due to its role as an
antioxidant.
Selenium functions as an antioxidant by
serving as a cofactor for the enzyme glutathione
peroxidase (Levander & Burk 1996). This
enzyme catalyses the reduction of organic perox-
ides, including the tissue damaging hydrogen
peroxide (H 2 O 2 ) (Hunt & Groff 1990). The reduc-
tion of peroxides renders them harmless.
Glutathione (GSH) reacts with H 2 O 2 , thereby
‘inactivating’ it to produce glutathione
disulphide (GSSG; the oxidized form of glu-
tathione). Also, glutathione reacts with organic
peroxides formed by an increase in the hydroxyl
radical.
Exercise increases oxygen consumption which
can lead to an increase in free radicals, such as
superoxide, by the incomplete reduction of
oxygen in the electron transport system. Super-
oxide is converted to hydrogen peroxide by the
enzyme superoxide dismutase (SOD) or can
form the hydroxy radical. Thus, the increased
hydroxy radicals and hydrogen peroxide levels
can be rendered harmless by glutathione peroxi-
dase and its essential cofactor selenium.