is also the possibility that these excessive
amounts may be harmful to health (see Chapter
20).
In the following sections, for each of the
vitamin, there will be a brief description of
exercise-induced changes in vitamin status and
requirements, the effects of vitamin supple-
ments, harmful effects of overdoses of vitamin
intakes and the main food resources of vitamins
(see Chapter 20). Vitamins are commonly classi-
fied into two groups, the fat soluble and the
water soluble. Vitamins A, D, E and K are fat
soluble. Vitamin C and members of the vitamin B
complex are water soluble. Fat-soluble vitamins
can be stored in appreciable amounts in the body,
and their function is largely independent of
energy metabolism. Water-soluble vitamins are
not stored in large quantities in the body and
must be ingested on a regular basis. Clinical
symptoms can be developed in individuals with
a diet deficient in B vitamins. Vitamin B 12 can be
stored in the liver for a year or longer.
Thiamin (vitamin B 1 )
Vitamin B 1 as thiaminpyrophosphate (TPP,
cocarboxylase), plays an important role in the
oxidative decarboxylation of pyruvate to acetyl-
coenzyme A (CoA) for entry into the Krebs cycle
and subsequent oxidation to provide for adeno-
sine triphosphate resynthesis. Thus, there is a
possibility that the increased demand for acetyl-
CoA during exercise would not be met in athletes
with a thiamin deficiency. If this occurred, more
pyruvate would be accumulated and converted
to lactate, with the possibility that fatigue would
develop more rapidly and aerobic performance
could be impaired. Thiamin deficiency could
also result in a reduced availability of succinate,
a coingredient of haeme, leading to inadequate
haemoglobin formation, another factor that
could influence aerobic exercise capacity. How-
ever, little evidence has shown that ingestion
of a vitamin B 1 supplement by athletes con-
suming a well-balanced diet has any effect on
performance.
It has been noted that there is a good linear
relationship between thiamin intake and energy
intake (van der Beek 1994). It is generally
accepted that the vitamin B 1 requirement is
dependent on the total energy expenditure and is
influenced by carbohydrate intake because
vitamin B 1 is essential for the intermediary
metabolism of carbohydrate. The vitamin B 1 nec-
essary to meet the body’s requirement intake
may vary according to energy intake (Clarkson
1991), and 0.5 mg thiamin · 4.2 MJ–1(1000 kcal–1) is
recommended for adults in most countries (US
National Research Council 1989). Any increased
requirement induced by exercise should be met
by increased energy intake and well-balanced
diet. However, reports from the Soviet Union
in the early days indicated that the output of
urinary vitamin B 1 of athletes decreased as the
training load increased; it was reported that
blood pyruvate levels increased by 30–40% as
compared with sedentary individuals when
vitamin B 1 intake was 2–3 mg · day–1(Yakovlev
1957). In order to keep pyruvate at normal levels,
it was recommended that the vitamin B 1 intake
should be 3–5 mg · day–1in the general popula-
tion and 5–10 mg · day–1for athletes undergoing
endurance training (Yakovlev 1957). Vytchikova
(1958) indicated that the usual content of thiamin
1.5–2.0 mg · day–1in food rations of athletes is
considered insufficient and that medical obser-
vation recommend approximately 10–20 mg
daily supplementation.
Athletes do not have a lower intake of vitamin
B 1 than the RDA and only very few have any
signs of a biochemical deficiency (Fogelholm
1992), but athletes who are on energy-restricted
diets for weight control are likely to have a less
than adequate intake, and athletes who take
a high percentage of their energy from low
nutrient-density food such as candy, soda, etc.
may be at risk (Clarkson 1991). Nutrition surveys
in Chinese elite athletes indicated that about half
of the athletes investigated had vitamin B 1
intakes that were lower than the RDA. The
average dietary intakes of vitamin B 1 of the
athletes undergoing vigorous training was 0.37–