estimated because many of these athletes have
consumed high protein diets regularly for 20–30
years or more.
Similarly, the association between high protein
diets and atherogenesis is likely overstated. For
example, it appears that the well-documented
positive relationship between animal protein
and plasma cholesterol observed in animals
doesn’t apply to humans (West & Beynen 1985)
and, as a result, the association between dietary
fat and blood fats is much weaker than once
thought (McNamara et al. 1987; Clifton & Nestel
1996). Furthermore, even if these relationships
are strong in sedentary individuals, the fate of
ingested fat may be substantially different
in physically active individuals (used as a fuel
rather than stored in blood vessel walls or
adipose tissue; Muoio et al. 1994; Leddy et al.
1997).
At one time it appeared that high protein diets
resulted in an obligatory loss of calcium in the
urine (Allen et al. 1979) and, if so, this could
be problematic, especially for women, because
of the potential to accelerate the development
of osteoporosis. However, this appears to be a
concern only with purified protein supplements
because the phosphate content of protein food
apparently negates this accelerated calcium loss
(Flynn 1985).
There are, however, at least two areas of
concern with high protein diets. First, the addi-
tional water excretion associated with the nitro-
gen loss via the kidneys could be detrimental
in physically active individuals (especially
endurance athletes) because of their already
increased fluid losses as sweat. The resulting
dehydration could adversely affect exercise per-
formance (Armstrong et al. 1985) and, if severe
enough, even threaten health (Adolph 1947;
Bauman 1995). For this reason, it is critical that
rehydration be adequate in athletes who ingest
high protein diets. The best way to do this is by
regularly monitoring changes in body mass. Dra-
matic acute weight changes in athletes consum-
ing high protein diets indicate that additional
rehydration is required. Second, the intake of
megadoses of individual amino acids (which has
only become possible in recent years with the
widespread commercial development of indi-
vidual amino acid supplements) could poten-
tially be detrimental. The ergogenic benefits of
these food supplements are promoted to athletes
very successfully because of the intense desire
of most athletes to excell. Although many of
the theoretical benefits sound convincing (espe-
cially to the non-scientist), few are documented,
despite considerable investigation (Brodan et al.
1974; Kasai et al. 1978; Isidori et al. 1981; Maughan
& Sadler 1983; Segura & Ventura 1988; Wessen
et al. 1988; Bucci et al. 1990; Blomstrand et al.
1991; Kreider et al. 1992, 1996; Fogelholm et al.
1993; Lambert et al. 1993; Newsholme & Parry-
Billings 1994; Bigard et al. 1996; Wagenmakers &
van Hall 1996; Suminski et al. 1997), and substan-
tial potential complications exist (Harper et al.
1970; Benevenga & Steele 1984; Yokogoshi et al.
1987; Tenman & Hainline 1991). As a result,
it is recommended that these supplements be
avoided until such time as their safety as well as
their ergogenic benefits are proven.Protein supplementation:
is it necessary?
Protein supplementation is probably not neces-
sary for the vast majority of physically active
individuals because the amounts of protein
found to be necessary (1.2–1.8 g · kg–1· day–1) can
be obtained in one’s diet assuming total energy
intake is adequate. For example, a sedentary
individual consuming about 10.5 MJ · day–1
(2500 kcal · day–1), of which 10% is protein, would
be consuming about 63 g protein daily. Assuming
a body mass of 70 kg, this would be about 0.9 g
protein · kg–1· day–1or about 112% of the current
protein RDA in most countries. Should this indi-
vidual begin an exercise programme and, conse-
quently, double his/her energy intake to 21 MJ
(5000 kcal) while maintaining 10% protein
intake, the resulting protein intake would also
double to 1.8 g · kg–1· day–1. This would be suffi-
cient to cover the increased needs of all the