Introduction
Many athletes steadfastly believe that there
exists a single nutritional ingredient that will
suddenly transform them into world champions.
Yet, to the best of our knowledge, the only sub-
stances that may confer such advantages to a
competitor are already on the International
Olympic Committee’s list of banned substances.
But, ever alert to commercial opportunities, mar-
keters of nutritional supplements for athletes
continue to make extravagant claims for the
performance-enhancing effects of their products.
Sports practitioners need to be aware that there
exist few controls to regulate the extent of the
claims that such nutritional companies can make
for the effectiveness of their products. Unlike the
pharmaceutical industry, which requires that all
product claims be substantiated by the results of
costly, controlled clinical trials, no such control is
required in the marketing of nutritional supple-
ments for sport. It is therefore not surprising to
find that athletes are often confused about the
extent to which nutrition can improve
performance.
In this review we analyse the scientific basis
for the nutritional practices of athletes, with
special reference to distance runners. We believe
that although nutrition is important for success,
it is only part of a balanced approach. As
Olympic gold and silver marathon medallist
Frank Shorter has said: ‘You don’t run 5 minutes
a mile for 26 miles on good looks and a secret
recipe.’
What do athletes eat and what should
they eat during training?
The major nutritional concern for athletes is the
excess energy expended during strenuous train-
ing, which, if not matched by an increased
energy consumption, will inevitably result in a
reduced training capacity and a drop in perfor-
mance. Top-class athletes undergoing strenuous
training can have daily energy expenditures two
to three times greater than untrained, weight-
matched individuals. This greater energy expen-
diture may exceed nutritional intake if only
normal eating patterns are maintained and could
explain the nibbling patterns of eating among
athletes.
The macronutrient intakes of well-trained
male and female middle- and long-distance
runners reported in a review of published
studies (Hawley et al. 1995a) are summarized in
Tables 42.1 and 42.2. A mean weighted carbohy-
drate (CHO) intake of 48% of total energy con-
sumption was reported by both male and female
runners. However, in contrast to male distance
runners who usually consume sufficient energy
to meet daily training requirements, the energy
intake of many of the female athletes was lower
than would be expected, given their workload.
Among female athletes, iron, zinc, vitamin B 12
and calcium intakes were also below the recom-
mended daily allowance.
It has long been proposed that the optimum
diet for athletes, especially for endurance
runners, should contain up to 70% of energy