in numbers of neutrophils, was sustained in the
sample taken at 1 h postexercise. A substantial
decrease, to below baseline, was observed in
numbers of circulating T-cells 1 h after exhaus-
tive exercise. However, there was a 30% decrease
in total lymphocytes at the same time point.
There was no significant difference in leucocyte
or lymphocyte numbers between the glutamine
and the placebo group. The provision of glu-
tamine appeared to have a beneficial effect
upon the ratio of CD4 to CD8 T-cells (Castell &
Newsholme 1997). A decrease in this ratio has
been suggested as being a possible cause and
indicator of immunosuppression in athletes
(Nash 1986; Keast et al.1988; Shepherd et al.
1991).
Questionnaires were given during the studies
to establish the incidence of infection for 7 days
after exercise (for details, see Castell et al.1996).
Completed questionnaires on the incidence of
infection were received from more than 200
individuals in 14 studies, who participated in
rowing, or endurance or middle-distance
running. The levels of infection were lowest in
middle-distance runners, and were highest in
runners after a full or ultramarathon and in elite
rowers after a period of intensive training (Table
11.4). The majority of the infections reported
were URTIs. Athletes who consumed two drinks,
containing either glutamine or a placebo, imme-
diately after and 2 h after a marathon, also com-
pleted 7-day questionnaires (n=151). Overall,
the level of infections reported by the glutamine
group was considerably less than that reported
by the placebo group (Table 11.5). A simple expla-
nation for the effects of glutamine observed in
these studies may be the fact that its provision
after prolonged exercise might make more gluta-
mine available for key cells of the immune
system at a critical time for induction of infection.
This series of studies provide more evidence
for the fact that prolonged, exhaustive exercise
such as a marathon produces a response which is
analogous to some aspects of the acute phase
response. Increases were demonstrated in acute
phase response markers, such as C-reactive
protein, interleukin 6 and complement C5a in
blood samples taken after a marathon race
(Castellet al.1997). An increase in the activation
of complement indicates enhanced macrophage
activity which may be involved in clearance of
fragments from damaged muscle tissue. The
fourfold increase in the plasma concentration of
C-reactive protein, observed 16 h after the race, is
consistent with damage to muscle after pro-
longed, exhaustive exercise.
The studies also confirm observations made
by others (for reviews, see Brenner et al.1994;
Nieman 1994a; Shinkai et al.1994), viz. that, after
marathon running, decreases occurred in the
numbers of some circulating immune cells which
were sustained until at least the next day (Castell
et al.1997). In one glutamine feeding study in this
series, the numbers of circulating lymphocytes,amino acids, fatigue and immunodepression 165
Table 11.4Incidence of infections in athletes during
7 days after different types of exercise (mean
values±SEM). After Castell et al. (1996a), with
permission.
No. of No. of Infections
Event studies participants (%)
Marathon 5 88 46.8±4.8
Ultramarathon 2 40 43.3±4.8
Mid-distance race 3 41 24.7±4.0
Rowing 4 45 54.5±7.8
Table 11.5Overall incidence of infections during
7 days for athletes given either glutamine or placebo
after running a marathon (mean values±SEM). After
Castellet al. (1996a), with permission.No. of Participants
participants with no
with no reported
No. of reported infections
participants infections (%)Glutamine 72 57 80.8±4.2*
Placebo 79 31 48.8±7.4* Statistical significance between glutamine and
placebo groups (P<0.001).