NUTRITION IN SPORT

1996). The volume of fluid contained within the
meal plus water was the same as the volume of
sports drink consumed, but the volume of urine
produced following food and water ingestion
was less than that when the sports drink was
consumed (Table 19.1). Although the amount of
water consumed with both rehydration methods
was the same, the meal had a greater sodium and
potassium content and it seems most likely that
the greater efficacy of the meal plus water treat-
ment in restoring whole body water balance was
a consequence of the greater total cation content.

Alcohol consumption

Because of the well-known diuretic properties of
alcohol and caffeine, it is usual to advise against
the consumption of drinks containing these sub-
stances when fluid replacement is a priority.
However, many people enjoy consuming these
beverages, and where large volumes of fluid
must be consumed in a relatively short time, a
wide choice of drinks will help to stimulate
consumption. In many sports, particularly team
sports, alcohol intake is a part of the culture of
the sport, and athletes are resistant to sugges-
tions that they should abstain completely (see
Chapter 30). However, it is now apparent that the
diuretic effect expected from alcohol, over and
above an alcohol-free beverage having otherwise
the same composition, is blunted when con-
sumed by individuals who are moderately hypo-
hydrated from exercise in a warm environment
(Shirreffs & Maughan 1997a).
After exercise, subjects consumed beer shandy

262 nutrition and exercise

(a peculiarly British drink produced by mixing

beer with lemonade) containing 0%, 1%, 2% or

4% alcohol. The volume of urine excreted for the

6 h following drink ingestion was related to the

quantity of alcohol consumed, but despite a ten-

dency for the urinary output to increase with

increasing alcohol intake, only with the 4% bev-

erage did the increased value approach signifi-

cance. The calculated decrease in plasma volume

with dehydration was approximately 7.6%

across all trials. With rehydration, the plasma

volume increased, but the rate of increase

seemed to be related to the quantity of alcohol

consumed; 6 h after finishing drinking, the

increase in plasma volume relative to the dehy-

drated value was approximately 8% with 0%

alcohol, 7% with 1%, 6% with 2% and 5% with

4%. It may be worth noting that the high sugar

content of lemonade (10%) means that beer

shandy has a carbohydrate content of about 5%,

and this carbohydrate may play an important

role in the restoration of muscle and liver glyco-

gen stores after exercise.

Voluntary fluid intake

The information from the work described above

was obtained from studies in which a fixed

volume of fluid was consumed. In practice,

however, intake will be determined by the

interaction of physiological and psychological

factors. A second consequence of ingestion of

plain water is to remove the drive to drink by

causing plasma osmolality and sodium concen-

tration to fall (Nose et al. 1988b). Where a fixed

Table 19.1Fluid consumed, quantities of major electrolytes ingested and volume of urine produced. Values in
brackets are mean (SEM) or median (range) as appropriate.

Meal+water Sports drink

Fluid volume (ml) 2076 (131) 2042 (132)

Electrolytes ingested (mmol)

Na+ 63 (4) 43 (3)

K+ 21 (1) 7 (1)

6 h urine volume (ml) 665 (396–1190) 934 (550–1403)