immediately felt tired. When, on iron pills, their
serum ferritin rose to 90mg·l–1, they felt three
times stronger (despite no rise in haemoglobin).
Alas, later, off iron pills, when their ferritin fell
again to 30mg·l–1, they felt weak again.
This myth is a Hydra; it keeps growing new
heads. It stems from misinterpreting research on
rodents—research probing the extent to which,
in the face of iron deficiency, exercise capacity is
limited by impaired oxygen delivery(anaemia)
vs. impaired oxygen use(impaired oxidative
metabolism in muscle). This model is not rele-
vant to athletes because it first creates severe iron
deficiency anaemiaand muscle iron deficiency in
weanling rats (deprived of dietary iron) and
then, by blood transfusion, reverses only the
anaemia. When this is done, the rats cannot run
maximally because, although they are no longer
anaemic, their muscles are still iron deficient
(Dallman 1982).
This research was misread on two counts. One,
it is a model of severe, ‘lifelong,’ bodywide iron
deficiency with severe anaemia. As such, it is at
the opposite end of the spectrum (of iron defi-
ciency) from the athlete who has low ferritin but
no anaemia yet. Two, as the rats grew ever more
deficient in iron, there was a parallel decrease in
all haem proteins measured (haemoglobin,
cytochrome c, myoglobin). In other words, when
haemoglobin was still normal, muscle myoglo-
bin and iron-containing enzymes were also still
normal. These rats developed ‘iron deficient
muscles’ as they got anaemic. Rats—and
athletes—with low ferritin but no anaemia have
normal muscles.
Fortunately, accumulating studies may kill the
Hydra. In one study (Celsing et al. 1986), mild
iron deficiency anaemia was induced by vene-
section of nine healthy men. When the anaemia
(but not the iron deficiency) was obviated by
transfusion, the subjects’ exercise capacity was
unchanged from baseline. Also, the activity of
iron-containing muscle enzymes remained
normal. Three studies now show that when non-
anaemic women with ferritin of less than 20mg·
l–1or less than 25mg·l–1are randomized to iron
therapy vs. placebo for 8 weeks, neither group
334 nutrition and exercise
improves in work performance or endurance
capacity (Newhouse et al. 1989; Fogelholm et al.
1992; Klingshirn et al. 1992). In two other studies
in which mildly anaemic women were random-
ized to iron vs. placebo, performance improved
only as anaemia was reversed (Schoene et al.
1983; LaManca & Haymes 1993). Finally, a recent
study analyses the 10 most relevant articles in
this field and concludes that low serum ferritin in
the absence of frank anaemia is not associated
with reduced endurance performance (Garza et
al.1997). It adds that ferritin can be used to detect
‘prelatent anaemias,’ but not as an independent
marker for performance in athletes. Amen.Increasing iron supply
The pre-eminent cause of iron deficiency in
women in sports (as in all women) is inadequate
dietary iron. Athletic women, notably ‘low-
bodyweight’ athletes, are notorious for consum-
ing too few calories. The recommended dietary
allowance (RDA) for iron is 10 mg · day–1for chil-
dren to age 10 and males 15 and above (some say
18 and above), 12 mg · day–1for boys 11–15 years,
and 15 mg · day–1 for females 11–50 years
(Clarkson & Haymes 1995). Yet many elite fe-
male athletes consume no more than 8400 kJ
(2000 kcal) daily, for a total of 12 mg of iron.
Also, because some female athletes are modi-
fied vegetarians, much of their dietary iron is not
highly bioavailable. Meats are an excellent
source of iron because they contain haem iron,
which is easily absorbed. In contrast, cereals,
legumes, whole grain or enriched breads and
deep green leafy vegetables contain non-haem
iron, which is not so easily absorbed. Four
studies agree that some active or athletic women
get too little iron. In one study, female recre-
ational runners who were modified vegetarians
had low ferritin levels, only one third those of
counterparts who ate red meat (Snyder et al.
1989). In another study of distance runners, the
men met the RDA for iron but the women did not
(Weight et al. 1992b). In a study of active women
in a university community, ferritins were highest
in those who consumed red meat (Worthington-