Introduction
Vitamins are a group of organic compounds
required in tiny amounts in the diet of humans
for proper biological functioning and mainte-
nance of health. Vitamins do not supply energy,
but act mainly as regulators of the numerous and
diverse physiological processes in the human
body including vision, skin integrity, bone
ossification, DNA formation, metabolism of
carbohydrate, fat, and proteins, mitochondrial
metabolism, utilization of oxygen in the cells, red
blood cell (RBC) formation and other functions
which are closely related to energy production
and resultant physical performance (see Chapter
20). The human body is not able to synthesize the
majority of the vitamins or the amount synthe-
sized in the body cannot meet the needs. It is
clear that a certain amount of each of the vita-
mins is essential in the diet and that lack of a
specific vitamin can cause a specific deficiency
disease (Williams 1985; Daniel 1991; Chen & Wu
1996). Due to the many and varied roles of vita-
mins, they are probably the most widespread
nutrients taken as supplements by both the
general and athletic population. Furthermore,
vitamins meet with great interest in the world of
sports because of their supposed role in enhanc-
ing physical performance (Williams 1989; van
der Beek 1991, 1994; Singh et al. 1992b; Weight et
al.1998a, 1998b).
Exercise enhances energy metabolism and
increases the total energy expenditure which
gives rise to a number of concerns:
- Does exercise training result in increased
needs or deficiencies of vitamins? - Is the vitamin status of athletes normal?
- Is it necessary for athletes to take vitamin
supplements?
The answers to these questions have varied
through the years and the balance of opinion
continues to change as new evidence appears
(Clarkson 1991, 1995; van der Beek 1991;
Fogelholm 1994; Armstrong & Maresh 1996). The
focal points of the concerns for vitamin nutrition
of athletes are the assumption that athletes
need an increased vitamin intake, the optimum
recommended dietary allowance (RDA) for ath-
letes under different conditions, and the true
effects of vitamin supplementation on physical
performance.
It is accepted that the prevalence of vitamin
deficiency diseases is low in the general popula-
tion in industrialized societies. Theoretically, the
athlete may have an increased requirement for
dietary intake of vitamins induced by decreased
absorption in the gastrointestinal tract, increased
excretion in sweat, urine and faeces, increased
turnover, as well as the adaptation for the initial
stage of vigorous training and/or acute physical
exercise which may enhance energy metabolism
(van der Beek 1991, 1994). It is generally agreed
that moderate physical activity per sedoes not
adversely affect vitamin status when recom-
mended amounts of vitamins are consumed in
the diet (Clarkson 1991). Marginal vitamin defi-
ciencies have been observed in athletes, but
many of the published reports of vitamin defi-