cellular oxidation-reduction reactions. Vitamin C
also helps non-haem iron absorption, transport
and storage. The deemed benefits of the effects of
vitamin C supplements include stimulation of
immune function and resistance to infection
(Chen 1988) and a reduction in fatigue and
muscle soreness, enhancing performance capac-
ity and protecting cells from free radical damage
(Kanter 1994), and thus it is perhaps the most
widely used and studied of the vitamins.
The US RDA for vitamin C is 60 mg · day–1(US
National Research Council 1989), but recom-
mended intakes vary widely between countries.
In some countries, specific recommendations
have been made for athletes, and the RDA for
vitamin C has been set at 140 mg · day–1during
training and 200 mg · day–1during competition
periods for Chinese athletes on the basis of main-
taining vitamin C in a saturation status as shown
by urinary output (Chen et al. 1962, 1963, 1992).
Most athlete groups studied have been reported
to exceed the RDA for vitamin C, but a small per-
centage of athletes, particularly young gymnasts,
have been found to have a less than adequate
intake of vitamin C (Loosli et al. 1986; Chen et al.
1989). Megadoses of vitamin C can cause iron
loading, may affect the availability of vitamin B 12
from food, and may also promote the formation
of urinary stones, yet high intakes of vitamin C
are relatively harmless (Clarkson 1991). A single
bout of exercise may increase blood levels of
ascorbic acid but decrease the ascorbic acid
content of other tissues (Chen et al. 1965; Gleeson
et al. 1987). Increases in plasma ascorbic acid
levels correlate significantly with the increase in
plasma cortisol, suggesting that exercise may
cause ascorbic acid to be released from the
adrenal gland or other organs into the circulation
along with the release of cortisol. The effect of
vitamin C supplementation on physical perfor-
mance has been investigated intermittently over
the past 50 years, but the results of these studies
have been contradictory. The possible benefits of
vitamin C supplementation on exercise-induced
muscle damage remain doubtful and need
further study.
Vitamin C is present in fresh fruits and vegeta-
bles, primarily the citrus fruits such as oranges,
grapefruit, lemons and limes. Other good
sources are broccoli, green peppers and greens.
There is little doubt that a severe deficiency of
vitamin C would have an adverse effect on work
performance: the feelings of weakness and lassi-
tude and the possibility of iron deficiency
anaemia would certainly not be beneficial
(Hodges 1980). Exercise may increase moder-
ately the body’s need for vitamin C, but to what
extent exercise training will change an athlete’s
requirement for vitamin C is still not entirely
clear. However, the inclusion of additional fruits
and vegetables in the athletes’ diet is advised.Vitamin A (retinol)
Vitamin A designates several compounds includ-
ing retinol, retinaldehyde and retinoic acid.
Vitamin A plays a major role in maintenance of
proper vision and epithelial tissues, and is also
involved in the development of bones and teeth
as well as playing an important function in the
body’s immune response. b-carotene, the major
carotenoid precursor of vitamin A, plays a role as
an antioxidant. The need for vitamin A can be
met by intake of carotenoid precursors com-
monly found in plants. The RDA for vitamin A is
expressed in retinol equivalents (RE); one
RE equals 1mg retinol or 6mgb-carotene. The
RDA for vitamin A is 1000 RE (1000mg retinol or
6000 mgb-carotene) for adult males and 800 RE
(800mg retinol or 4800mgb-carotene) for adult
females (US National Research Council 1989).
Russian research suggested that extra vitamin A
is needed in athletes requiring good visual acuity
and alertness and during periods of stress
(Williams 1985). The RDA for vitamin A for
Chinese athletes was set at 1500 RE · day–1(Chen
et al. 1992).
The vitamin A intake of elite athletes has gen-
erally been found to be adequate, although it has
been reported that 10–25% of the athletes investi-
gated were ingesting less vitamin A than the
RDA (Clarkson 1991). Studies that have assessed
the vitamin A, C and E status of athletes have
found that most had adequate blood levels of