letes have adequate blood zinc levels (Weight et
al.1988; Fogelholm & Lahtinen 1991; Fogelholm
et al. 1991, 1992a; Bazzarre et al. 1993; Lukaski
1997). However, many endurance athletes were
found to have relatively low resting blood
levels of zinc (Dressendorfer & Sockolov 1980;
Haralambie 1981; Dressendorfer et al. 1982;
Deusteret al. 1986; Couzy et al. 1990; Marrella et
al.1990; Singh et al. 1990), and Singh et al. (1989)
reported low blood zinc levels in a significant
number of Navy Seals.
Deusteret al. (1986) did not find a strong cor-
relation between dietary zinc intake and
serum zinc, although they did find a relationship
between zinc intake and red blood cell zinc.
Relying on plasma or serum zinc as a measure of
status will probably not show impaired zinc
status when indeed it may occur. In a study of
induced zinc deficiency, Prasad (1991) found that
5 mg zinc · day–1did not result in a decrease in
plasma zinc until 4–5 months. However, zinc
concentration in lymphocytes, granulocytes and
platelets decreased within 8–12 weeks and
may be a more sensitive indicator of mild zinc
deficiency.
Exercise can result in a loss of zinc in the sweat
as well as the urine (Anderson et al. 1984; Van Rij
et al. 1986; Anderson & Guttman 1988). Couzy et
al.(1990) found that serum zinc was significantly
decreased after 5 months of intensive training.
Because the lower zinc values could not be
explained by changes in dietary habits, plasma
protein concentration, hormonal changes, or
infection, they were considered to result from the
stress of exercise. However, Manore et al. (1993)
reported that after 6 weeks of an aerobic training
programme, there was a significant decrease in
plasma zinc but at 12 weeks the values were back
to baseline, suggesting only a transient change.
Also, subjects who were on a combination of
anaerobic and aerobic exercise programmes
did not show a change in plasma zinc.
Hübner-Woz ́niak et al. (1996) found that plasma
zinc increased after 10 weeks of weight training,
and Ohno et al. (1990) reported that 10 weeks of
training resulted in an increase in erythrocyte
levels of zinc, but no change in plasma zinc.
Fogelholm (1992) suggested that the increase
340 nutrition and exercise
in erythrocyte zinc may reflect a high concentra-
tion of zinc-dependent enzymes as a result of
training.
Examination of changes in blood levels of zinc
after an acute bout of exercise may prove helpful
in understanding the chronic effects of exercise.
However, the results of these studies are equi-
vocal (Dressendorfer et al. 1982; Anderson et al.
1984; Ohno et al. 1985; Marrella et al. 1993). High-
intensity exercise appears to produce an increase
in plasma zinc while endurance activity either
showed no change or a decrease (Bordin et al.
1993; Lukaski 1997). Increases may be due to a
redistribution of zinc. For example, zinc may be
released from erythrocytes in response to exer-
cise or may be released from muscle (Lukaski
1997). Aruoma et al. (1988) suggested that a
decrease in plasma zinc immediately after exer-
cise may reflect an acute phase response to exer-
cise stress. Postexercise changes in plasma zinc
levels were found to be sensitive to the zinc
status of the individual, and this may affect the
variability in response (Lukaski et al. 1984). The
changes that occur are temporary, returning to
baseline within a few hours to a day.
Dressendorfer et al. (1982) found that over a 20-
day road race, plasma zinc increased on the first
exercise day but thereafter returned to near base-
line values.
From the above studies it appears that an
acute bout of exercise induces an alteration in
zinc distribution in the blood. Because zinc is
an integral part of carbonic anhydrase in
erythrocytes, erythrocytes may serve as a readily
exchangeable store zinc (Ohno et al. 1995).
Further study of the process of redistribution of
zinc among body compartments is needed to
understand how exercise can exert an effect on
zinc status. When examining chronic changes in
zinc status due to training, the activity level of
the subjects must be carefully controlled prior to
taking samples because of the variable responses
to an acute exercise bout.Performance and supplementation
Few studies examined the relationship between
zinc status and performance or the effects of