The Vegetarian Athlete

Chapter 33
The Vegetarian Athlete
JACQUELINE R. BERNING
Introduction
All athletes at some time in their career look
at alternative ways of eating to reach their athletic potential. While some athletes take pills,
powders or potions in the belief that these will
enhance their performance, others have changed
their eating styles to a vegetarian diet to gain
advantages in training and performance. Unfortunately, after many years of research, the effects
of elimination of animal products from the diet
on athletic performance are still unclear. Some
data do exist on elite athletes who consume
a vegetarian diet, but studies that include
Olympic-calibre athletes are limited. In addition,
most of the research on vegetarianism in the past
decade has been focused on the health aspects of
a vegetarian diet, rather than on human performance issues. There is certainly a lack of information regarding vegetarianism and its relationship
to athletic performance. However, an athlete
who consumes a poorly planned vegetarian diet
may be at risk of multiple nutritional deficiencies
as well as poor physical performance.
Early meat eaters
It well known that ancient Greek athletes consumed large amounts of meats and many of them
believed that their performances were dependent upon animal protein. As an example, Milo
of Croton, the legendary Greek wrestler, consumed huge amounts of animal protein and
trained by carrying animals across his shoulders.
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As the animals grew, so did his strength. While
Milo’s diet would be viewed today as containing
excessive amounts of protein, he was never
brought to his knees in the course of the five
Olympiads in which he competed (Ryan 1981;
Whorton 1982). This concept of the need for large
amounts of animal protein was promoted in the
early 1800s by Liebig, the pre-eminent physiological chemist of the time (Whorton 1982). He
believed that protein was the main substrate for
the exercising muscle. While Liebig’s hypothesis
was disproved by Atwater in the mid-1800s,
his philosophy of consuming large amounts of
protein continues to have influence even into the
modern day. Today, many athletes still believe
that, by consuming large amounts of protein,
they will become stronger and gain lean body
mass (Berning et al. 1991).
Early vegetarians
While many ancient Greeks were consuming
large amounts of animal protein for athletic
prowess, the founder of the philosophical vegetarian movement was also Greek. Pythagoras,
the Greek mathematician, is the father of
vegetarianism, and until the middle of the 19th
century, vegetarians referred to themselves as
‘Pythagoreans’ (Dombrowski 1984).
Many of the vegetarians in the mid- to late
1800s were determined to prove that their diet
was superior to that of meat eaters. As a result,
the London Vegetarian Society formed an athletic and cycling club in the late 1800s to compete
the vegetarian athlete
against their carnivorous counterparts and in
most cases outperformed them in athletic competition (Nieman 1988). Due to their success,
many other vegetarian athletes joined the movement. One such competition was the 1893 race
from Berlin to Vienna, a 599-km course in which
the first two competitors to finish were vegetarian (Whorton 1982). Over the next 10–20 years
many other vegetarian athletes performed well
in endurance performances around Europe.
Because of the success of vegetarian athletes,
a few researchers in the early part of the 20th
century were interested in measuring their physical capabilities, and Fischer (1907) conducted
experiments on Yale student athletes. The subjects were exposed to a wide variety of foods
including meat and meatless choices and performed a variety of endurance tests. Those athletes who gravitated toward the meatless diet
were classified as vegetarians and were compared with athletes who ate meat. Each subject
was tested to determine the maximum length of
time that they could hold their arms out horizontally and the number of maximum deep knee
bends and leg raises they could perform. Fischer
noted that the vegetarians scored better than
their meat-eating counterparts.
Wishart (1934) reported on a 48-year-old
Olympic cyclist who had been a vegetarian for
23 years. The subject was submitted to four different meatless meals with different levels of
protein during the 4-week experimental period.
The exercise protocol involved riding a cycle
ergometer for 8.5 h on four occasions after stabilizing on a different level of dietary protein.
During the ride, measurements were made of
external work and total energy expenditure.
Higher speeds were recorded on the cycle
ergometer after consuming the diets with a
higher protein content, especially after 4 h of
riding. The improved performance was attributed to an increased supply of energy coming
from the meatless protein foods. While the
energy content of each of the four different meatless meals varied by about 840 kJ (200 kcal), the
amount of carbohydrate was not calculated and
the increase in protein content for each of the
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four experimental diets came from dairy products which contain a significant amount of
carbohydrates.
Modern-day vegetarian athletes
The recent literature contains few publications
dealing with vegetarianism and athletic performance. However, Cotes et al. (1970) studied the
effect of a vegan diet on physiological responses
to submaximal exercise in 14 females who had
consumed a vegetarian diet for an average of
more than 11 years. They compared the vegetarians with two different controls, one that
included 66 females of comparable social background and a second group of 20 office cleaners
who had a comparable level of activity to that of
the vegetarians. All subjects performed a submaximal test on a cycle ergometer in which they
cycled for 3 min at 30 and 60 W. Ventilation and
cardiac frequency were obtained as well as width
of the muscles in the thigh. Their results showed
that the sedentary controls had a significantly
higher cardiac frequency while having a significantly lower grade of activity (P > 0.02). No statistical differences exist between the groups for
thigh circumference or anterior skinfold thickness. The authors concluded that the data do not
support the hypothesis that a low dietary intake
of animal protein impairs the physiological
response to submaximal exercise.
Few data exist on the relationship between
athleticism and vegetarian diets even today, in
spite of the popular belief that a vegetarian diet
may be beneficial to some athletes. However,
anecdotal reports abound. The Tarahumara, a
Ute-Aztecan tribe inhabiting the Sierra Madre
Occidental Mountains in the north central state
of Chihuahua, Mexico, have been reported to be
capable of extraordinary physical fitness and
endurance as long-distance runners (Balke &
Snow 1965), while consuming a vegetarian diet.
Their diet contains very little food from animal
sources and they have reportedly run distances
up to 320 km in ‘kickball’ races which often last
several days (Balka & Snow 1965). Cerqueira and
associates (1979) investigated the Tarahumaras’
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special considerations
food intake and nutrient composition and
reported that most of their daily energy and
nutrients come from corn, beans and squash.
About 94% of their daily protein intake is from
vegetable sources and only 6% from animal
sources. Since most of the fat in their diet (9–12%)
was derived from corn, beans and squash, their
diets are rich in linoleic acid and plant sterols.
The Tarahumara diet is extremely low in cholesterol (71 mg · day–1) since their primary source of
cholesterol is eggs, of which they consume about
two or three per week. Other sources of fat and
cholesterol in the Tarahumara diet come from
small, infrequent servings of meat, fish, poultry
and dairy products and lard. Even though the
diet of the Tarahumara Indians is a simple one
consisting mainly of plant foods, it is of high
nutritional quality and is nutritionally sound,
resulting in little chronic deficiencies and no
widespread undernutrition (Cerqueira et al.
1979).
Hanne et al. (1986) investigated various fitness
parameters of vegetarian athletes and compared
them with non-vegetarians. Forty-nine athletes
(29 men and 20 women) who had been either
lacto-ovo- or lactovegetarian for at least 2 years
were compared with 49 controls (29 men and 20
women). Subject ages ranged from 17 to 60 years
of age, with the majority of the subjects in the
age range of 17–35 years. Fitness parameters
included anthropometric measurements, pulmonary function, aerobic and anaerobic capacity
and blood chemistries. The authors found no significant differences in body mass between the
two groups, although the female vegetarians had
a significantly (P > 0.01) high percentage body
fat than their non-vegetarian counterparts. No
differences were found in pulmonary function,
heart rate, blood pressure or in the electrocardiogram. No differences were found between the
two groups of subjects in aerobic capacity or
anaerobic capacity as determined from a submaximal test and a Wingate test, respectively.
Results from the blood examination found that
non-vegetarian controls had lower uric acid
levels than the vegetarian males, but the nonvegetarian group were within the normal range.
Vegetarian women had lower haematocrit values
than controls, but haemoglobin, total protein,
and glucose were similar in both groups. While
no differences were found between the two
groups, it is always difficult to find significant
differences, because vegetarianism does not
embrace a single, well-defined diet, and the
influence of other lifestyle factors, including
habitual physical activity levels, may obscure
possible effects of the diet itself. Herein may lie
part of the problem, as past research on vegetarianism and athletic performance did not clearly
define the type of diet being followed by groups
of individuals studied. Many athletes may call
themselves vegetarian when in fact they simply
eliminate from their diet a food group or a certain
class of foods. Information on the diet of vegetarian athletes would be helpful in defining limiting
or beneficial factors.
Classifications of vegetarian diets
Vegetarian diets range from the vegan diet,
which excludes all animal proteins, to the semivegetarian diet, which may include some animal
proteins (Table 33.1).
Whatever the term an individual uses, it
appears that vegetarianism is a continuum of
eating styles, which range from the sole consumption of plant foods to a diet restricting certain kinds of animal proteins or limiting
the frequency of animal protein consumption
(Ratzin 1995). Because of the variety of vegetarian eating styles among practitioners, it is difficult to define the variables that will influence
human performance, but relationships have been
found between vegetarianism and a reduction in
specific health risks.
Health implications of
vegetarian diets
There is increasing tendency among researchers
to conclude that the reduced disease risk
observed among vegetarians is not explained so
much by the absence of meat from the diet, but
by the fact that they eat more plant foods. Results
the vegetarian athlete
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Table 33.1 Classifications of various types of vegetarian diets. From Rudd (1989), with permission.
Diet
Description
Semivegetarian
Some but not all groups of animal-derived products, such as meat, poultry, fish,
seafood, eggs, milk and milk products may be included in this diet
New vegetarian
Plant-food diet supplemented with some groups of animal products, but emphasis is
placed on foods that are ‘organic, natural and unprocessed or unrefined’
Pescovegetarian
Excludes red meats, but consumes fish as well as plant foods
Lacto-ovovegetarian
Milk and milk products and eggs included in this diet, but meat, poultry, fish, seafood
and eggs excluded
Ovovegetarians
Eggs are included in this diet, but milk and milk products, meat, poultry, fish and
seafood are excluded
Strict vegetarian/vegan
All animal-derived foods, including meat, poultry, fish, seafood, eggs, milk and milk
products are excluded from this diet
Macrobiotic
Avoids all animal foods. Uses only unprocessed, unrefined, natural and organic foods.
In some types there is fluid restriction. Tamari, miso and various seaweeds are used
Fruitarian
This diet consists of raw or dried fruits, nuts, seeds, honey and vegetable oil
of epidemiological research are traditionally
expressed in terms of relative risk, a difficult
concept for the athletic and consumer population
to grasp. In a recent re-examination of data from
the Adventist Health Study (Fraser et al. 1995),
novel statistical calculations show how certain
effects may delay or advance the first expression
of disease. The Adventist Health Study is a
cohort investigation of approximately 34 000 Californian, non-Hispanic, white subjects living in
Seventh Day Adventist households who were
followed for 6 years. Some of the findings from
this study are as follows.
1 Non-vegetarians develop coronary disease
1.77 years earlier than vegetarians.
2 Among males, non-vegetarians have a remaining lifetime risk of developing coronary disease that is 11.9% higher (P < 0.05) than that of
vegetarians.
3 Non-vegetarian females have a remaining lifetime risk of developing coronary disease that is
0.26 percentage points lower than that of female
vegetarians.
4 Those who rarely consume nuts develop coronary disease 2.6 years earlier and have a remaining lifetime risk 11.9 percentage points greater
(P < 0.05) than persons who eat nuts at least
five times per week.
While Seventh Day Adventists show a reduced
risk of several chronic diseases, many of them
also abstain from smoking and alcohol, and they
are more physically active than non-vegetarians,
which also affects the prevalence of chronic diseases. To date, no one has followed a vegetarian
athletic population to see if they show the same
health benefits.
Nutritional adequacy of
vegetarian diets
Protein quality
A nutritionally sound vegetarian diet is possible
if adequate amounts of a wide variety of foods
are consumed (Grandjean 1989; Harding et al.
1996), but there are certain nutrients that vegetarians must be aware of and plan for to ensure
the presence of adequate amounts in their diets.
The most obvious nutrient of concern is
protein. Lacto-ovovegetarians and ovovegetarians receive high-quality complete proteins and
are unlikely to incur protein deficiencies. Vege-
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special considerations
tarians who consume only plant proteins could
become protein deficient unless they balance
their amino acids. Plant proteins are incomplete
and lack one or more essential amino acid. While
it was once thought that all the amino acids must
be consumed in one meal, it is now agreed that
timing of the amino acid intake is less critical and
that amino acid intake must be balanced over
days rather than hours. Research now shows that
the liver monitors the amino acid composition of
proteins consumed in a meal: if the meal is low in
an essential amino acid, the liver can break down
its own proteins to supply it. When the amino
acid is once again plentiful, the liver will replenish its protein source.
Because individual plant foods do not contain
all the essential amino acids, it is recommended
that vegetarians complement their proteins. For
example, cereals are very low in the essential
amino acid lysine, while legumes are slightly
deficient in the sulphur-containing amino acids.
By combining these two groups of foods (i.e.
refried beans and corn tortillas), a vegetarian
could provide a mixture of amino acids similar to
that of a complete or high-quality protein food.
Figure 33.1 illustrates different combinations of
incomplete proteins to make a complete protein
as well as demonstrating the fact that when an
animal protein is combined with an incomplete
Milk
products
Rice with sesame seeds
Pe
Ri
ce
an
an
ut
d
bu
be
tte
an
rs
ca
an
dw
sse ich
ro
le
Protein requirements for vegetarian athletes
A major concern for vegetarian athletes is to
make sure that they have consumed enough food
so that their protein requirement will be met. The
total protein intake of athletes consuming a vegetarian diet may have to be increased slightly to
take account of the lower digestibility, lower
energy density and lower protein quality of plant
foods consumed. This may lead to problems with
the volume of food to be consumed, because athletes with high energy requirements may find it
difficult to consume sufficient volume of foods to
maintain energy balance on a purely vegetarian
diet. Generally, if vegetarian athletes consume
between 0.8 and 1.7 g protein · kg–1 body mass ·
day–1 and maintain energy balance, they should
meet their protein requirement for exercise and
health.
Vitamin B12
Another nutrient that may be low in a vegetarian
diet is vitamin B12, especially for those individuals on a strict plant-based diet (vegans). Rauma et
al. (1995) studied the vitamin B12 status of long-
Nuts
and
seeds
Sunflower seed
and
peanuts
Macaroni and cheese
cereal with milk
Grains
protein, the result is a complete, high-quality
protein.
Milk in legume soups
Legumes
Fig. 33.1 The concept of mutual
supplementation, which is the strategy of
combining two incomplete sources of
protein so that the amino acids in each food
make up for those lacking in other foods.
Such protein combinations are sometimes
called complementary proteins.
the vegetarian athlete
term adherents to a strict uncooked vegan diet
called the ‘living food diet’ (LFD). Most food
items in this diet are fermented or sprouted.
Serum B12 concentrations and the dietary intakes
of 21 long-term adherents of the LFD were compared with those of 21 omnivorous controls. In a
longitudinal study, the LFD diet resulted in a
decrease in serum vitamin B12 in six of nine subjects. The cross-sectional study revealed significantly lower serum vitamin B12 in the LFD
adherents than in their matched omnivorous
controls. Those following the LFD who consumed nori or chinerilla seaweeds had somewhat better B12 status than those who did not, but
B12 levels fell over time in all but one subject.
While lower levels of vitamin B12 have been
found in strict vegans, few cases of clinical deficiency have been found. Helman and DarntonHill (1987) found the mean serum vitamin B12
levels of vegetarians to be significantly lower
(350 pg · ml–1) than those of omnivores (490 pg ·
ml–1), while 16% of the vegetarians had values
less than 200 pg · ml–1. Vitamin B12 deficiency is
rare among lacto-ovovegetarians because milk
and eggs contain sufficient quantities of this
nutrient. Vegans should be encouraged to use
soybean milk fortified with vitamin B12 or a
vitamin B12 supplement. Analogues of the
vitamin found in algae, spirulina, nori or fermented soy products do not have vitamin activity for humans.
Individuals with low serum B12 may manifest
paraesthesia (numbness and tingling in the
hands and legs), weakness, fatigue, loss of
vibration and position sense, and a range of
psychiatric disorders including disorientation,
depression and memory loss. The use of alcohol,
tobacco and drugs such as antacids, neomycin,
colchicine and aminosalicylic acid may contribute to the problem by causing B12 malabsorption in both omnivores and vegetarians.
less risk of iron deficiency anaemia. In absolute
amounts, red meat contains only an average
amount of iron, but the bioavailabilty of iron
from red meat is superior to that derived from
plant sources. There are two forms of iron in
the diet: haem iron and non-haem iron. Haem
iron found in meats, fish and poultry is better
absorbed than non-haem iron, which is found in
grains, vegetables and fruits. The fractional
absorption of haem and non-haem iron varies
between 3% and 35%, depending on the presence
of dietary enhancing factors such as ascorbic
acid, consumption of sources of haem iron and
on the body stores of iron. Table 33.2 lists the
ranges of intestinal absorption of iron from haem
and non-haem food sources which is dependent
upon body stores of iron.
Iron is classified as an essential nutrient and is
required for the formation of haemoglobin and
myoglobin, as well as the cytochromes, which
are components of the electron transport chain in
the mitochondria. Iron is also a cofactor for a
number of enzymatic reactions, including those
involved in the synthesis of collagen and of
various neurotransmitters. In addition, iron is
needed for proper immune function and plays a
role in the drug detoxification pathways
(Wardlaw & Insel 1995).
Since iron plays a critical role in oxidative
energy metabolism, it is essential for athletes to
have adequate iron stores. There are some differences of opinion about the prevalence of iron
deficiency among athletes. A number of studies
have used serum ferritin as a measure of iron
deficiency anaemia, while other studies have
used haemoglobin and haematocrit as determinants of iron deficiency anaemia. The number
Table 33.2 Absorption rate (as % of intake) of haem
and non-haem iron in relation to body stores of iron.
Haem
(%)
Non-haem
(%)
Low stores of iron
35
20
Normal stores of iron
15
Iron availability in vegetarian diets
While both vegetarian and non-vegetarians may
have difficulty in meeting the dietary requirements for iron, athletes who eat red meat are at
447
2–3
448
special considerations
of athletes suffering from true iron deficiency anaemia is therefore difficult to establish
(Eichner 1988). Further debates have been
sparked by the fact that many athletes with low
iron stores eat little haem iron and yet have
no performance decrements (Dallongeville et al.
1989; Snyder et al. 1989; Lyle et al. 1992; Pate et al.
1993; Williford et al. 1993). It is, however, important to monitor iron status among athletes, especially female athletes. The Sports Medicine and
Science Division of the United States Olympic
Committee recommend screening for haemoglobin and haematocrit twice yearly. Other tests
of iron stores are recommended based on menstruation records.
Snyder et al. (1989) investigated the iron intake
and iron stores in female athletes who either
were consuming a mixed diet or were classified
as a modified vegetarian. The subjects were
matched for age, body mass, aerobic capacity,
training load and number of pregnancies. The
modified vegetarians (n = 9) consumed less than
100 g of red meat per week while the subjects on
the mixed diet (n = 9) included red meat in their
diet. Both groups consumed the same amount of
iron (14 mg · day–1), but serum ferritin and total
iron-binding capacity were significantly lower in
the modified vegetarian group (P < 0.05). The
authors also found that the bioavailability of the
iron consumed by the two groups was different.
Iron consumed by the modified vegetarian
group was significantly less available than the
iron consumed by the mixed-diet group. These
data suggest that in female runners non-haem
iron may not be as readily available as haem iron.
These findings have also been confirmed in the
non-athletic population. In 1995 Shaw et al.
(1995) investigated the iron status of young
Chinese Buddhist vegetarians (23 men and 32
women) and compared them with non-vegetarian students (20 men and 39 women). Dietary
assessment of iron intake and haematological
measurements of biochemical indices, including
haemoglobin, plasma iron, transferrin saturation
and plasma ferritin, were made. A characteristic
of the vegetarian diets was that most of the
protein was coming from soybean products,
which have limited bioavailable iron. Daily iron
intake was similar in both vegetarian and nonvegetarian men, but iron intake was significantly
higher in female vegetarians than nonvegetarians. Results from the haematological
measurements showed that for both sexes, the
median plasma ferritin concentration of the vegetarians was about half that of the nonvegetarians. There was also a greater prevalence
of low ferritin levels and anaemia in the vegetarian group, especially among the vegetarian
women.
food strategies for increasing
iron in a vegetarian diet
Because animal foods are the best and most
absorbable source of iron, this presents a potential problem to the vegetarian who eats no red
meat. Lacto-ovovegetarians also have a problem
consuming enough iron, as milk and dairy
products are poor sources of iron. Vegetarians
can incorporate leafy green vegetables such as
spinach and legumes as well as fortified and
enriched whole grains into their diets. Dried fruit
can also provide iron in the vegetarian diet.
Dietary iron may also be derived from iron
cooking utensils. When acidic foods are cooked
in iron cookware, some of the iron is taken up
with the food.
Zinc status among athletes
Since the best food sources of zinc are meats,
dairy products and seafood (especially oysters),
zinc nutriture is of concern for vegetarians.
Whole-grain cereals and cereal products are the
primary sources of zinc in many vegetarian diets,
but the phytate and fibre content of these products reduces the bioavailability of zinc (Reinhold
et al. 1976). Zinc is found in almost every tissue in
the body and is a cofactor for over 100 enzymes,
of which several are important in the pathways
for energy metabolism. Zinc is also needed
for protein synthesis and is a part of the insulin
molecule.
Several studies have demonstrated that
the vegetarian athlete
exercise increases zinc loss from the body
(Dressendorfer & Socklov 1980; Haralambie
1981; Singh et al. 1990; Clarkson & Haymes 1994)
and that levels may be low in athletes. Possible
explanations for the reduced level of zinc stores
include inadequate intake of zinc, low bioavailability, increased zinc loss during exercise, dilution of zinc by expansion of plasma volume, and
redistribution of zinc in the body.
Contrary to these reports, Lukaski (1989;
Lukaski et al. 1990) has found that zinc status is
not affected by physical training as long as
dietary intakes of zinc are adequate. Lukaski et al.
(1990) studied 16 female and 13 male swimmers
and 13 female and 15 male non-swimming
controls. Plasma zinc values were within the
normal range for all subjects and did not change
throughout the swimming season. In addition to
Lukaski’s studies, Duester et al. (1989) investigated the effects of endurance training on zinc
status in 13 highly trained women and compared
them with 10 untrained controls. Three-day
dietary records were evaluated for zinc intake
while blood and 24 h urine samples were taken
before and after a 25-mg oral zinc load. Mean
daily zinc intakes did not differ and were below
the recommended dietary allowance set for zinc
for both groups. The authors reported no differences between fasting concentrations of plasma
zinc, serum albumin, a-2-macroglobulin, and
erythrocyte zinc content among the two groups.
However, the trained women had significantly
(P < 0.05) higher urinary zinc excretion and
reduced responses to the oral zinc load than did
the untrained women. The authors concluded
that the increase in zinc excretion in the highly
trained women may reflect higher rates of skeletal muscle turnover.
zinc and the vegetarian
In addition to these studies of athletes, several
studies confirm lower zinc status among
vegetarians (Freeland-Graves et al. 1980; Gibson
1994; Kadrabova et al. 1995).
Janelle and Barr (1995) recently reported
a study comparing nutrient intakes between
449
female vegetarians and non-vegetarians with
similar health practices and found that vegans
and lactovegetarians had lower zinc intakes
(8.5 and 8.2 mg · day–1, respectively) than the
recommended dietary allowance of 15 mg · day–1.
Similar results were found in a study conducted
by Donovan and Gibson (1995), who found that
33% of semivegetarians, 24% of lacto-ovovegetarians and 18% of omnivores had serum zinc
levels below 10.7 nmol · l–1. They also reported
that the phytate to zinc ratio in the diet was negatively associated with the serum zinc concentration (P < 0.05). The authors concluded that the
suboptimal zinc status was the result of low
intakes of poorly available zinc in all dietary
groups.
food strategies for increasing
zinc in a vegetarian diet
Foods for the vegetarian that have the highest
zinc content are oysters, crab, shrimp, wheat
germ and legumes. Incorporating other good
sources of zinc into a vegetarian diet will also
help meet the dietary recommendations: nuts,
beans and whole grains can all contribute. Zinc is
not part of the enrichment process, so refined
flours are not a good source.
Calcium requirements of vegetarians
The diets of strict vegetarians or vegans tend to
be low in calcium unless adequate amounts of
milk and dairy products or dark leafy greens
are consumed daily. As with iron and zinc, the
absorption of calcium may be reduced by phytates, oxalates, fibre and tannins (James et al.
1978; Weaver et al. 1996). Phytic acid is found in
oatmeal and other whole-grain cereals, while
oxalates are commonly found in beets, spinach
and leafy greens. These binders seem to depress
absorption of calcium present in some calciumcontaining foods but not in others. That is why
strict vegans who obtain most of their dietary
calcium from leafy greens and whole-grain products are at a greater risk of an inadequate calcium
availability than milk-drinking vegetarians. A
450
special considerations
purely vegan diet may also be low in vitamin D,
which will further impair calcium absorption
and utilization.
In an interesting anthropological study of
prehispanic burials from the Canary Islands,
Gonzalez-Reimers and Arnay-de-la-Rosa (1992)
found a high prevalance of osteoporosis among
the 117 skeletons analysed for trace elements.
Bone trace element analysis showed that low
concentrations of iron, zinc and copper were
found in skeletons with a reduced trabecular
bone mass. The authors state that during this prehispanic period many of the residents of the
Canary Islands existed in a relative proteinenergy malnutrition state which consisted
mainly of a vegetarian diet which may have predisposed these individuals to osteoporosis.
It has been suggested that vegetarians who
restrict their intake of dairy products should
provide calcium-rich foods or supplements by
consuming calcium-fortified soy products as
well as consuming dark leafy green vegetables
on a daily basis.
food strategies for increasing
calcium in a vegetarian diet
Foods with the highest nutrient density for
calcium are leafy greens, such as spinach and
broccoli, non-fat milk, romano cheese, swiss
cheese, sardines and canned salmon. The
calcium found in some leafy greens is not well
absorbed because of the presence of oxalic acid,
but this effect is not as strong for kale, collard,
turnip, and mustard greens. Overall, nonfat milk is the most nutrient-dense source of
calcium because of its high bioavailability and
low energy value. The new calcium-fortified
orange juices and other beverages offer an alternative to the individual who is a strict vegetarian; other calcium-fortified foods include bread,
breakfast cereal, breakfast bars, and snacks.
Another good source for the vegetarian is
soybean curd (tofu) if it is made with calcium carbonate (check the food label).
While there are concerns about the potential
lack of some nutrients in a vegetarian diet, many
of these concerns can be overcome by using a
wide variety of foods and planning meals so that
they complement proteins and include nutrientdense foods. Table 33.3 summarizes the nutrients
that may be lacking in a vegetarian diet and
gives some examples of foods that could be included in a vegetarian diet to overcome these
inadequacies.
Hormonal alterations as a result of
a vegetarian diet
There is evidence that nutritional status and diet
can affect the reproductive system. Hill et al.
(1984) found that Caucasian women (n = 16), who
normally ate meat had a significantly (P < 0.01)
shorter follicular phase of their second menstrual
cycle when they ate a vegetarian diet for two
cycles. The vegetarian diet decreased (P < 0.01)
the pituitary response to releasing luteinizing
hormone and decreased (P < 0.05) the episodic
release of luteinizing hormone. The experiment
also included supplementing nine vegetarian
Black South African women with daily meat
product: an increased length of the follicular
phase was observed (P < 0.01). The authors
concluded that a lower episodic release of
gonadotrophins and a shorter duration of the
follicular phase, when omnivorous women ate
no animal protein, implies that a vegetarian diet
plays a role in the control of ovulation through
the hypothalamic axis of the central nervous
system. In a similar study, Pirke et al. (1986)
investigated the influence of a vegetarian diet
on the menstrual cycles of 18 healthy normal
weight women aged 17–27 years. Plasma levels
of oestradiol, progesterone and luteinizing
hormone were measured on Monday, Wednesday and Friday throughout the 6-week diet
period. Nine women followed a vegetarian diet
while nine followed an omnivorous diet. Both
groups lost weight during the experimental
period (1 kg body weight · week–1). Seven of the
nine vegetarian women became anovulatory and
had significantly decreased luteinizing hormone
during the mid-cycle and luteal phase. Oestrogen and progesterone levels were also signifi-
the vegetarian athlete
451
Table 33.3 Nutrients 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
component of antibodies, enzymes,
hormones; responsible for
transport of nutrients and fluid
balance
Eggs, fish, legumes, peanut butter,
milk, brown rice, peanuts,
soybeans
Vitamin B12
2.0 mg ◊ day-1
Promotes growth; cofactor for
several enzymes; maintains the
sheath around nerve fibres; helps
folate in preventing anaemia
Eggs, dairy products, clams,
oysters, some seafood
Iron
Males, 10 mg ◊ day-1;
females, 15 mg ◊ day-1
Constituent of haemoglobin and
myoglobin; carrier of O2 and CO2
Clams, whole grains, enriched
cereals, green leafy vegetables,
dried fruits, tofu, legumes
Calcium
Teens, 1200 mg ◊ day-1;
adults, 800 mg ◊ day-1
Major component of
hydroxyapatite for bones and teeth;
regulation of muscle contraction,
heart beat, clotting of blood, and
transmission of nerve impulses;
blood pressure
Dairy products, leafy green
vegetables, fish and shellfish, tofu,
legumes
Zinc
Males, 15 mg ◊ day-1;
females, 12 mg ◊ day-1
Part of over 100 enzymes;
associated with insulin; involved in
making DNA and RNA; involved
with the immune system; transport
of vitamin A; wound healing and
normal development of the fetus
Fish, oysters, dairy products,
black beans, kidney beans, tofu,
beets, peas, whole-grain breads,
bran flakes
Vitamin D
400 IU ◊ day-1
Promotes normal bone and teeth
formation; aids body’s absorption,
transportation and deposition of
calcium and phosphorus
Fortified dairy products, egg yolk,
shrimp, sunlight
cantly decreased in the vegetarian group. In comparison, seven of nine women in the omnivorous
group maintained ovulatory cycles and had no
change in cycle length or in the length of the follicular phase. In both of these studies a vegetarian 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 provided some possible reasons why a vegetarian
diet may play a role in menstrual-cycle regularity. 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,
both in vitro and in 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 may
452
special considerations
induce production of sex hormone-binding
globulin in the liver and in this way influence
sex hormone metabolism and biological effects.
Indeed, Gorbach and Goldin (1987) measured
urinary, faecal and plasma levels of oestrogens in
pre- and postmenopausal women eating different diets. Premenopausal US women consuming
a ‘Western’ diet composed of 40% fat and low
fibre were compared with age-matched vegetarians eating 30% of their energy intake as fat and
a high-fibre diet. The researchers found that
the vegetarian women excreted threefold more
oestrogen in their faeces, had lower urinary
oestrogen excretion, and had 15–20% lower
plasma oestrogen than the omnivorous women.
When pre- and postmenopausal women eating a
Western diet were compared with Asian immigrants eating a very low fat diet (20–25% of total
energy from fat), similar results were found,
except that the plasma oestrogen levels were 30%
lower among the Orientals than in the Western
omnivore group. Correlation analysis of dietary
components and plasma oestrogen showed that
plasma oestrogen was positively associated with
fat intake and negatively associated with dietary
fibre. The authors concluded that diets high in
fibre, like a vegetarian diet, can alter the route of
excretion of oestrogen by influencing the enterohepatic circulation and thus influence plasma
levels of oestrogen. In a similar study, Pedersen et
al. (1991) examined the effect of different nutritional patterns on menstrual regularity in premenopausal women. Forty-one non-vegetarian
and 34 vegetarian women were recruited and
completed a questionnaire regarding menstrual
history and a 3-day dietary record. The reported
incidence of menstrual irregularity was 4.9%
among the non-vegetarians and 26.5% among
the vegetarians. The vegetarian group consumed
significantly more polyunsaturated fatty acids,
carbohydrates, vitamin B6 and dietary fibre,
whereas the non-vegetarians consumed significantly more caffeine, cholesterol, saturated fatty
acids and alcohol. Logistic regression analysis
showed that the probability of menstrual regularity among all subjects was positively correlated with increasing protein and cholesterol
intakes. The probability of developing menstrual
irregularities was negatively correlated with
increasing dietary fibre and increasing amounts
of magnesium in the diet. This study is consistent
with the notion that premenopausal vegetarian
women as a group have decreased circulating
oestrogen concentrations.
Additional data from Adlercreutz et al. (1986a)
have also found that vegetarians may be excreting more oestrogen than omnivores: they investigated the possible effects of variations in dietary
fibre intake on oestrogen metabolism in young
Finnish women through one winter and one
summer. Eleven of the subjects were lactovegetarians, while 12 were omnivorous. Within the
groups there was a seasonal variation in fibre
intake. The vegetarian group consumed more
fibre (P < 0.02), more grains (P < 0.02) and more
vegetables (P < 0.02) during the winter than
during the summer. The excretion of oestrogens
was remarkably constant in the omnivorous
group, while the vegetarian group had a significant seasonal variation of total and individual
catecho-oestrogens and estrone (P < 0.05–0.005).
There were no differences between the groups in
excretion of total or individual urinary oestrogens in any season or between mean values for
both seasons, but a significant negative correlation was found between dietary intake of total
grain fibre per kilogram of body weight and the
excretion of individual oestrogens were found.
These studies are consistent with the notion that
menstrual regularity can be influenced by specific dietary nutrients that may have a direct
effect on oestrogen.
Hormonal responses of a vegetarian lifestyle
on males
Most of the data collected on diet and hormone
relationships among vegetarians is on women,
and information on males is sparse. Howie and
Shultz (1985) studied the relationship between
dietary nutrients and plama testosterone, 5-adihydrotestosterone, oestradiol-17-b, luteinizing
hormone, and prolactin levels in 12 Seventh Day
Adventist vegetarian, 10 Seventh Day Adventist
the vegetarian athlete
non-vegetarian and 8 non-Seventh Day Adventist, 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-b were significantly lower in the
Seventh Day Adventist vegetarians than in the
ominvores. Additionally, plasma levels of testosterone and oestradiol-17-b of all subjects were
negatively correlated with dietary fibre intake.
The authors concluded that a vegetarian eating
style may lead to decreased plasma concentrations of androgens and oestrogens in men. In
contrast, Naik and Snyder (1997) examined the
independent effects of diet and endurance training on basal serum testosterone concentration by
comparing endurance-trained cyclists with vegetarian individuals who had abstained from
eating red meat and poultry for 1 year. The
aerobic ability of the endurance athletes was significantly greater than that of the sedentary vegetarians. 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 compromised 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% vegetarian) with regularly menstruating runners (13%
vegetarian) and found that the runners with
453
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 menstrual 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 regularly 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 relationship between athletic amenorrhoea and bone
health, there is a limited amount of information
on the possible effects of a vegetarian lifestyle.
Hunt et 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 omnivores 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 menstrual irregularities among the vegetarian subjects. These studies support the concept that,
despite the differences in dietary practices, vegetarian and non-vegetarian women do not appear
to differ in bone health. Caution must be taken,
454
special considerations
however, when dealing with an athlete who is a
vegetarian. Bone mineral densitiy should be
measured and adequate amounts of calcium
should be consumed to ward off the potential
harmful effects of low oestrogen on bone.
While vegetarianism is not a risk factor for the
Female Athlete Triad, it may become a factor if an
athlete is amenorrhoeic due to her vegetarian
eating pattern.
Conclusions and recommendations
Currently most information on vegetarianism
relates to nutritional adequacy and the implications for lifestyle diseases such as heart disease
and cancer. Little is known about the relationship between vegetarianism and athletic performance. What is clearly understood is that the
vegetarian athlete must plan his or her diet carefully to avoid the risk of nutritional deficiencies
and an adverse effect on performance. There are
advantages to the athlete of consuming a vegetarian diet. Vegetarian athletes usually consume
a higher proportion of energy in the form of carbohydrates. It is well documented that athletes,
especially endurance athletes, should be consuming a higher proportion of carbohydrates in
their diets to maximize muscle glycogen concentration. Prolonged strenuous exercise can deplete
most of the glycogen stored in the muscles
and the athlete can become chronically fatigued.
Increasing dietary carbohydrates will be beneficial to the athlete involved in heavy training.
More research is needed to answer some of the
current concerns of vegetarian athletes, especially with regard to hormonal alterations and
their impact on bone health as well as the questions on protein-energy requirements for strict
vegetarians who consume no animal protein.
If athletes adopt a vegetarian lifestyle, they
must become aware of the limitations of the
diet and make sure that their nutritional requirements are met so as not to influence performance.
Vegan diets should not be attempted by any
athlete without previous experience or without
consultation with a dietitian or health care
provider. Young growing athletes should be dis-
couraged from such a strict diet due to its possible limitations on growth and performance.
Vegan diets should only be considered if an
athlete is willing to devote time and effort to
understanding the proper combinations and
amounts of foods necessary to achieve a nutritionally balanced diet.
In planning vegetarian diets of any type, athletes should choose a wide variety of foods and
ensure that the energy intake is adequate to meet
their needs. Additionally, the American Dietetic
Association (1993) gives the following recommendations for individuals who are vegetarian
or thinking of becoming vegetarian.
• Keep the intake of foods with a low nutrient
density, such as sweets and fatty foods, to a
minimum.
• Choose whole or unrefined grain products,
instead of refined products, whenever possible,
or use fortified or enriched cereal products.
• Use a variety of fruits and vegetables, including a good food source of vitamin C.
• If milk or dairy products are consumed, use
low-fat or non-fat varieties.
• Limit egg intake to three or four per week.
• Vegans should have a reliable source of
vitamin B12, such as some fortified commercial
breakfast cereals, fortified soy beverage or a
cyanocobalamin supplement. As long as the
athlete is outdoors in the sun for part of the day,
supplemental vitamin D may not be needed.
• Vegetarian and non-vegetarian infants who
are solely breastfed beyond 4–6 months of age
should receive supplements of iron and vitamin
D if exposure to the sun is limited.
These recommendations, of course, were formulated for the non-athlete, and may need to be
modified. When energy intake is very high, for
example, there is room in the diet for foods
with low nutrient density without compromising nutritional status.
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