Introduction
Vitamins in sports
Vitamin supplements, including especially
vitamin C, but also the B-complex vitamins and
vitamin E, are frequently used by athletes (Sobal
& Marquart 1994). The common motivation for
vitamin supplementation is to improve sports
performance and enhance recovery (Williams
1986). Reversing the view, many athletes and
coaches fear that a normal diet will eventually
lead to marginal vitamin supply and to a deterio-
ration in sports performance.
As regards vitamins and optimal physical per-
formance, there are two questions with substan-
tial practical importance. First, if vitamin supply
is marginal, would an athlete’s functional capac-
ity be less than optimal? Second, if vitamins
are given in excess of daily needs, would
this improve functional capacity? This chapter
reviews the basic metabolic functions of different
vitamins (Table 20.1) and aims at giving answers
to the two above-mentioned questions. The
vitamin requirements of physically active people
are reviewed in Chapter 21, and antioxidant
functions in Chapter 22.
What are vitamins?
Vitamins are organic compounds required in
very small amounts (from a few micrograms to a
few milligrams on a daily basis) to prevent devel-
opment of clinical deficiency and deterioration in
health, growth and reproduction (McCormick
1986). A distinct feature of vitamins is that the
human body is not able to synthesize them. Clas-
sification of vitamins is based on their relative
solubility (McCormick 1986): fat-soluble vita-
mins (A, D, E and K) are more soluble in organic
solvents, and water-soluble vitamins (B-complex
and C) in water.
Ubiquinone and ‘vitamin B 15 ’ are examples
of compounds announced as ‘vitamins’ and as
ergogenic substances for athletes. Ubiquinone,
an electron carrier in the mitochondrial respira-
tory chain, is indeed needed for normal body
function and health, and it is found in a Western
mixed diet (Greenberg & Frishman 1988).
Nevertheless, because the body can synthesize
ubiquinone, the name ‘vitamin Q’ is misleading
and should not be used.
‘Vitamin B 15 ’, in contrast to ubiquinone, cannot
be synthesized by the human body. However,
it is not a vitamin, because there are no specific
diseases or signs associated with depletion. In
fact, ‘vitamin B 15 ’ in products with ergogenic
claims does not even have a well-defined
chemical identity (Williams 1986). There is no
evidence that supplementation with ubiqui-
none or ‘vitamin B 15 ’ would increase athletic
performance (Williams 1986; Laaksonen et al.
1995).Vitamin supply and functional capacity
Adequate nutritional status means a sufficiency
of the host nutriture to permit cells, tissues,