NUTRITION IN SPORT

terations to normal gastrointestinal tract function
have frequent clinical associates. These include
such uppergastrointestinal tract complaints as
nausea, vomiting, reflux, epigastric pain, bloat-
ing and excessive belching. Lower gastrointesti-
nal tract symptoms include altered bowel habit
(constipation or diarrhoea), rectal blood loss,
flatulence, the urge to defecate, abdominal
cramps and faecal incontinence (Brukner & Kahn
1993).
Various studies have reported the frequency of
symptomatic, gastrointestinal tract-affected ath-
letes to range from 50% (Brouns 1991; Wright
1991) to over 80% in a group of New Zealand
endurance athletes (Worobetz & Gerrard 1985). It
therefore behoves all sports physicians to recog-
nize the exercise-related symptoms of gastro-
intestinal tract dysfunction and offer appropriate
therapy.
This section will discuss some of the more
common symptoms related to gastrointestinal
tract dysfunction in athletes and describe them
on a regional basis.

Oesophageal symptoms

Symptoms including ‘heartburn’ and acid reflux

248 nutrition and exercise

are frequent associates of exercise, generally

thought to be linked to altered oesophageal

sphincter tone. A consequence of lowered

oesophageal sphincter pressure is disruption to

the unidirectional flow of upper gastrointestinal

tract contents. This is frequently reported to be

exacerbated by exercise, resulting in altered

oesophageal peristalsis, reflux and exposure

of the oesophagus to acid gastric contents

(Worobetz & Gerrard 1986; Larson & Fisher

1987; Moses 1990; Wright 1991; Green 1992;

Peterset al. 1993). The local irritant effect gives

rise to the unpleasant sensation of retrosternal

pain described colloquially as ‘heartburn’. It is

well recognized that the retrosternal discomfort

often precipitated by exercise may have cardio-

logical origins. Clinical wisdom demands a full

investigation in cases where the age, family

history and risk factors for ischaemic heart

disease coexist.

The ingestion of carbohydrate-rich supple-

ments was followed by bouts of cycling and

running in a study by Peters et al. (1993). This

association was found to correlate highly with

symptoms of nausea, belching, epigastric full-

ness (bloating), the urge to defecate, abdominal

cramps and flatulence. The mode of exercise as a

factor in provoking oesophageal symptoms was

investigated by Rehrer et al. (1992) in a group of

triathletes. These investigators found a higher

incidence of gastrointestinal tract symptoms

associated with running. Similar conclusions

were drawn by Sullivan (1994), who questioned

110 triathletes to find that running was as-

sociated with ‘a preponderance of gastro-

oesophageal and colonic symptoms’. However,

given the fact that the running section of a

triathlon is always preceded by the swim and

cycle phases, the results of these studies should

be interpreted with some caution. Factors such as

hydration status, fatigue level and posture are

possible influences of some significance. In fact,

Rehrer et al. (1990) identified a body weight loss

of 3.5–4.0% by dehydration, to be associated with

an increase in gastrointestinal tract symptoms in

runners.

Worobetz and Gerrard (1986) found that only

Table 18.1Common gastrointestinal symptoms
associated with exercise.

Symptom Possible contributing factors

Upper gastrointestinal
Nausea Dehydration
Vomiting Altered gastrointestinal
Reflux blood flow
Epigastric pain Altered gut permeability
Bloating Disturbed gastrointestinal
Belching motility

Lower gastrointestinal

Psychological

Constipation

influences

Diarrhoea

Pharmacological agents

Rectal blood loss
Flatulence
Urge to defecate
Abdominal cramps
Faecal incontinence