plus mineral mass to decrease (– 3.5%) on the
lower protein diet. In contrast, subjects (no
gender difference was apparent) on the higher
protein diet had a greater protein synthetic rate
and a tendency to increase whole-body protein
plus mineral mass (+1.9%). These data agree
with the findings in younger subjects (discussed
above) and further suggest that higher pro-
tein diets are beneficial for older individuals who
strength train. This is especially important
because as the benefits of strength training for
seniors become more apparent (Fiatarone et al.
1990; Fiatarone et al.1994), the number of older
individuals adding this type of exercise training
to their fitness/wellness programmes is growing
significantly.
There is other supportive evidence for the sug-
gestion that physically active individuals need
additional dietary protein (Consolazio et al. 1963,
1975; Celejowa & Homa 1970; Laritcheva et al.
1978; Marable et al. 1979; Dragan et al. 1985;
Meredith et al. 1992) and, taking these together
with the recent nitrogen balance and protein
turnover results, it is difficult to deny that protein
intakes in excess of the current recommendations
(0.8 g · kg–1· day–1in most countries) are benefi-
cial for those who are physically active. It
appears that the optimal protein intake for
strength athletes may be as high as 1.7–1.8 g ·
kg–1· day–1and for endurance athletes slightly
less, perhaps 1.2–1.4 g protein · kg–1· day–1.
However, as mentioned, these data have been
collected primarily on men. The limited data
available on female endurance athletes suggest
that dietary protein needs for women may be
somewhat less but this is not well documented.
Moreover, there are almost no data on female
body builders. Consequently, these nitrogen
balance and tracer studies need to be repeated
with female subjects to confirm the apparent
gender differences with endurance exercise and
to establish protein intake recommendations for
female strength athletes.
Currently, despite anecdotal claims to the
contrary, there is little good evidence that high
protein intakes (>1.3–1.4 g protein · kg–1· day–1)
144 nutrition and exercise
actually enhance muscle performance (Dragan
et al. 1985; Brouns et al. 1989; Vukovich et al. 1992;
Fryet al. 1993). Moreover, we did not observe
an enhanced endurance running performance
with supplemental protein in rodents undergo-
ing endurance training (Cortright et al. 1993) nor
could we document greater muscle strength or
mass gains in strength athletes with supplemen-
tal protein (2.6 g · kg–1· day–1) despite improved
nitrogen status (Lemon et al. 1992). Further, our
studies with differing protein types (soy, casein,
whey) and strength training have not revealed
any obvious performance advantage of any
particular type of protein (Appicelli et al. 1995).
However, our studies have only investigated the
initial response (4–8 weeks) to training and it is
possible that over longer time periods an advan-
tage could become apparent. Given the fantastic
claims and the obvious potential monetary bene-
fits in the athletic arena, it is somewhat surpris-
ing that this area has received such little attention
among scientists.Are these moderately high protein
recommendations healthy?
Many believe high protein diets are hazardous
but it is difficult to document an adverse effect
except in patients with impaired kidney function
(Brenner et al. 1982). Clearly, high dietary protein
increases the work of the kidneys because of the
additional nitrogen load that must be excreted,
but this does not seem to be a problem for
healthy individuals. In addition, serious adverse
effects have not been observed in rodents that
consumed extremely high protein diets (80% of
energy intake) for more than half their lifespan
(Zaragozaet al. 1987). These data are particularly
interesting not only because of their longitudinal
nature but also because this diet represents at
least three times the protein percentage observed
in the highest protein diets of athletes. Finally,
the absence of reports of kidney problems in
middle-aged weight lifters/body builders sug-
gests that the dangers of high protein diets in
healthy individuals have probably been over-