Micronutrient requirements in
competitive swimming
The only vitamin or mineral that has received
much attention in the literature on dietary habits
of competitive swimmers is iron. Perhaps the
reason for this is that swimmers tend to consume
a large amount of food and typically exceed the
RDA for most of the nutrients. However, there is
evidence of iron deficiency, particularly among
female swimmers, even when RDA is met.
Brighamet al. (1993) determined iron status in
25 female college swimmers on a biweekly basis
throughout a 25-week competitive season. In
addition, they examined the effectiveness of iron
supplementation during this season. Before
breaking the swimmers into an experimental
(iron supplement) and placebo group, these
authors observed that 17 of the swimmers had
depleted iron stores (defined as serum ferritin
concentration< 12 mg·l–1) while five of the swim-
mers were defined as anaemic (haemoglobin
<12 g · dl–1). During the 5 weeks in which the
experimental group received 39 mg elemental
iron as an iron supplement per day, haemoglobin
concentration increased in 24% of the subjects
and plasma ferritin concentration increased in
68% of the subjects. In the control group who did
not ingest an iron supplement, haemoglobin con-
centration decreased despite consuming a diet
containing 16.3 mg iron · day–1. These authors
concluded that moderate iron supplementation
is effective in preventing a decline in iron status
during swimming training but a higher dose
may be needed to reverse a pre-existing iron
deficiency.
Ganzitet al. (1993; cited in Burke 1993) tested
the effectiveness of 80 mg iron supplementation
per day in male and female swimmers. Swim-
mers in the experimental group maintained their
plasma ferritin levels while those swimmers in
the placebo group experienced a decrease in
plasma ferritin concentration. These authors
also noted an improvement in anaerobic capacity
and reduced lactic acid response to submaximal
exercise that was more marked in the experimen-
tal group than in the placebo group. In the
females, these improvements were confined
only to the group that received the dietary iron
supplement. Since haemoglobin concentrations
did not change in either of the groups, these
authors concluded that performance gains were
made at the level of iron-associated muscle
enzymes.
Walsh and McNaughton (1989) studied the
effects of 150 mg iron supplementation per day
on the haematology and V.
o2max.of competitive
female swimmers training at least 2 h · day–1and
7 days a week. During this period, the experi-
mental group had an increase in haemoglobin
concentration from 12.5 g · dl–1 before supple-
mentation to 13.6 g · dl–1after supplementation
with no change in the placebo group. Plasma fer-
ritin concentration dropped in the placebo group
from 28 to 16mg·l–1while no signficant change
was observed in the experimental group (26 to
21 mg·l–1). By the end of the study, 40% of the sub-
jects in the placebo group were classified as iron
deficient (serum ferritin £ 12 mg·l–1, haemoglobin
≥12 g · dl–1) and 10% of the subjects were clas-
sified as anaemic (serum ferritin £ 12 mg·l–1,
haemoglobin£12 g · dl–1). These data are shown
in Fig. 46.4. None of the swimmers who received
the iron supplement was classified as either
iron deficient or anaemic. These authors con-
cluded that young female swimmers should be
routinely tested for iron status and that iron
supplementation undertaken when deemed
necessary.Conclusion
The nutritional problems that have been summa-
rized in this chapter may all be linked to the
volume, frequency and intensity of training these
athletes perform. Thus, the difficulties in trying
to meet the energy demands, supply adequate
carbohydrate to fuel the exercise and aid recov-
ery, minimize muscle proteolysis, and prevent
iron depletion and the associated negative effects
on haematology could be avoided most simply
by reducing training. At the very least, swim-
ming coaches should design training pro-
grammes that lessen the risk of developing the