effect on serum growth hormone or insulin con-
centrations (Fogelholm et al. 1993). There seems
to be no substantial evidence to support the use
of these supplements.
The addition of medium-chain triglycerides,
which include fatty acids with a carbon chain
6–12 atoms long, to the diet of athletes is a new
phenomenon (Manore et al. 1993). Medium-chain
triglycerides are metabolized differently from
longer chain fatty acids. They are absorbed
rapidly in the gut and transported via the portal
vein to the liver, rather than through the lym-
phatic system in the form of chylomicrons. As
with longer chain fatty acids, oxidation occurs in
the mitochondria, but carnitine is not required
for transport across the mitochondrial mem-
brane. They are rapidly oxidized after ingestion.
The use of medium-chain triglycerides is
becoming popular with athletes, especially
bodybuilders, because they are energy dense
(35.3 kJ · g–1, 8.4 kcal · g–1), providing twice the
energy of carbohydrate on a weight basis. A
single dose of 25–30 g of medium-chain tri-
glycerides does not cause any gastrointestinal
problems, but some symptoms may occur with
higher doses (Berning 1996). They are, however,
relatively expensive. Also, ingestion of large
amounts will stimulate ketone body formation if
not consumed with an adequate amount of car-
bohydrate, and have a strong thermogenic effect.
Creatine supplementation in an appropriate
dose can provide improved performance for ath-
letes in explosive events: these include all events
lasting from a few seconds to a few minutes. The
effects and use of creatine are described fully in
Chapter 27. One commonly reported side-effect
is a gain in weight of 1–2 kg within a week of
beginning supplementation. Most of this extra
weight is accounted for by water, but this may
have implications for athletes in weight category
sports.
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