non-vegetarian and 8 non-Seventh Day Adven-
tist, non-vegetarian males. Fasting blood
samples and 3-day dietary intakes were obtained
from all subjects. The Seventh Day Adventist
vegetarians consumed significantly more crude
and dietary fibre than the other non-vegetarian
subjects. Plasma levels of testosterone and
oestradiol-17-bwere significantly lower in the
Seventh Day Adventist vegetarians than in the
ominvores. Additionally, plasma levels of testos-
terone and oestradiol-17-bof all subjects were
negatively correlated with dietary fibre intake.
The authors concluded that a vegetarian eating
style may lead to decreased plasma concentra-
tions of androgens and oestrogens in men. In
contrast, Naik and Snyder (1997) examined the
independent effects of diet and endurance train-
ing on basal serum testosterone concentration by
comparing endurance-trained cyclists with vege-
tarian individuals who had abstained from
eating red meat and poultry for 1 year. The
aerobic ability of the endurance athletes was sig-
nificantly greater than that of the sedentary vege-
tarians. Nutrient intake, however, was similar
in both groups, except for dietary fibre intake,
which was higher in the vegetarian group.
Serum total and free testosterone concentrations
were not different for either main effect (i.e. diet
and exercise). Perhaps the lack of difference in
sex hormones could be attributed to the fact that
the diets were very similar in both groups.
Implications of vegetarian diets
for athletes
Vegetarian diets have been associated with a low
incidence of cancers of the breast, endometrium
and prostate. However, lowered plasma levels
and increased urinary excretion of oestrogen can
lead to menstrual abnormalities which may in
turn lead to irregular menstrual cycles and com-
promised bone health in vegetarians. Brooks
et al.(1984) noted that most female athletes with
amenorrhoea were vegetarian. They compared
the diets of amenorrhoeic runners (82% vegetar-
ian) with regularly menstruating runners (13%
vegetarian) and found that the runners with
regular menstrual cycles ate five times more
meat and significantly (P<0.05) more fat than
amenorrhoeic runners. Kaiserauer et al.(1989)
also found that amenorrhoeic runners consumed
significantly less fat, red meat and total energy
than did regularly menstruating runners. Slavin
et al.(1984) found that there was a high incidence
of vegetarianism among amenorrhoeic athletes
and speculated that trace elements or plant
hormones may affect menstruation. While it
appears that vegetarianism may influence men-
strual function, the real importance of menstrual
irregularities in female athletes is related to bone
health.
In a landmark study on bone health and
athletic amenorrhoea, Drinkwater et al.(1984)
studied 28 female athletes, 14 of whom were
amenorrhoeic. When compared with the regu-
larly menstruating runners, the amenorrhoeic
runners had significantly lower lumbar vertebral
bone mineral densities. The mean age of the
amenorrhoeic athletes was 25 years, but their
average bone mineral density was equivalent to
that of a 51-year-old. While there is a clear rela-
tionship between athletic amenorrhoea and bone
health, there is a limited amount of information
on the possible effects of a vegetarian lifestyle.
Huntet al.(1989) investigated the relationship of
bone mineral content/bone width in elderly,
independently living Methodist omnivores and
Seventh Day Adventist vegetarians. Bone mass
was measured by single photon absorptiometry
and dietary intakes were assessed by 24-h
dietary recall and food frequency methods. Bone
mineral/bone width was not different in omni-
vores compared to vegetarians and no significant
relationships were found to exist between
current or early dietary intakes and bone
mineral/bone width. Lloyd et al.(1991) also
found no significant differences in bone density
between vegetarian and non-vegetarian women
despite a significantly higher prevalence of men-
strual irregularities among the vegetarian sub-
jects. These studies support the concept that,
despite the differences in dietary practices, vege-
tarian and non-vegetarian women do not appear
to differ in bone health. Caution must be taken,