cantly decreased in the vegetarian group. In com-
parison, seven of nine women in the omnivorous
group maintained ovulatory cycles and had no
change in cycle length or in the length of the fol-
licular phase. In both of these studies a vegetar-
ian diet appears to be involved in the incidence
of menstrual irregularities, but the underlying
pathophysiology remains unclear.
Vegetarian diets and oestrogen levels
Adlercreutz et al.(1986a, 1986b, 1995) have pro-
vided some possible reasons why a vegetarian
diet may play a role in menstrual-cycle regular-
ity. Dietary constituents such as fibre and a vege-
tarian eating pattern have been shown to alter
oestrogen levels in humans by influencing
oestrogen synthesis, availability, excretion
metabolism and action. Currently there is a great
deal of interest in plant-derived lignans and
isoflavonic phyto-oestrogens, as they have been
found in human urine and appear to exhibit,
bothin vitroandin vivo, weak oestrogenic and
sometimes anti-oestrogenic activities. Plant
lignans and isoflavonoids, glycosides from
soybean products as well as whole grains, seeds
and nuts are converted by intestinal microflora to
hormone-like compounds. These compounds
bind, with low affinity, to oestrogen receptors,
and preliminary results suggest that they maythe vegetarian athlete 451
Table 33.3Nutrients that are of concern in a vegetarian diet and strategies to lower nutritional deficiencies. From
Rudd (1990).
Nutrient RDA Physiological function Vegetarian food sources
Protein 0.8 g◊kg-^1 BW Build and repair tissues; major Eggs, fish, legumes, peanut butter,
component of antibodies, enzymes, milk, brown rice, peanuts,
hormones; responsible for soybeans
transport of nutrients and fluid
balance
Vitamin B 12 2.0mg◊day-^1 Promotes growth; cofactor for Eggs, dairy products, clams,
several enzymes; maintains the oysters, some seafood
sheath around nerve fibres; helps
folate in preventing anaemia
Iron Males, 10 mg◊day-^1 ; Constituent of haemoglobin and Clams, whole grains, enriched
females, 15 mg◊day-^1 myoglobin; carrier of O 2 and CO 2 cereals, green leafy vegetables,
dried fruits, tofu, legumes
Calcium Teens, 1200 mg◊day-^1 ; Major component of Dairy products, leafy green
adults, 800 mg◊day-^1 hydroxyapatite for bones and teeth; vegetables, fish and shellfish, tofu,
regulation of muscle contraction, legumes
heart beat, clotting of blood, and
transmission of nerve impulses;
blood pressure
Zinc Males, 15 mg◊day-^1 ; Part of over 100 enzymes; Fish, oysters, dairy products,
females, 12 mg◊day-^1 associated with insulin; involved in black beans, kidney beans, tofu,
making DNA and RNA; involved beets, peas, whole-grain breads,
with the immune system; transport bran flakes
of vitamin A; wound healing and
normal development of the fetus
Vitamin D 400 IU◊day-^1 Promotes normal bone and teeth Fortified dairy products, egg yolk,
formation; aids body’s absorption, shrimp, sunlight
transportation and deposition of
calcium and phosphorus