Effect of Vegetarian Diets on Performance in
Strength Sports Chris
Forbes-Ewan Sportscience
6, sportsci.org/jour/0201/cf-e.htm, 2002 (3479 words)
Arguments in
Favor of the Vegetarian Diet Body Composition
and Fitness of Vegetarians Does Meat-eating
Benefit Strength Athletes? |
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Non-vegetarian or omnivore: eats
foods of plant and animal origin, including meat, fowl, eggs, milk and other
dairy products, and fish. Lacto-ovovegetarian: eats
predominantly foods of plant origin, with milk and other dairy products and
eggs being the only foods of animal origin. Vegan: eats foods only of plant
origin. Last year
a lively debate took place on the Sportscience mailing list about the effects
of vegetarianism on sports performance, with particular reference to strength
sports. The debate began with an assertion on a non-professional mailing list
by a rock climber (who was not a nutritionist or physiologist) that a
vegetarian diet is inferior to an omnivorous diet for the maintenance of
strength and muscular endurance. He based this assertion on his personal
experience and observations of other rock climbers. I sent this message to
the Sportscience list
for comment. Here is a summary of the
debate, which I have updated with relevant references to published work and
some additional issues. View the
original messages by searching the list for vegetarian or viewing messages for June and July, 2001. Arguments in Favor of the Vegetarian Diet Bill
Proulx (Appalachian State University, North Carolina), Stacey Sims (Massey at
Wellington, New Zealand) and Deborah Shulman (address not provided)
independently pointed out that from a nutritional viewpoint, vegetarian diets
can provide all known essential nutrients in adequate quantities for strength
training. Proulx went further and stated that a vegetarian diet might be
expected to provide for better nutrition, with the exception of iron
and zinc status. Janelle and Barr (1995) provided supporting evidence for
generally more nutritious diets (at least with respect to health) among
vegetarian compared to non-vegetarian women. The vegetarians (n=23) had
significantly higher intakes of carbohydrate, riboflavin, niacin, vitamin B12,
folate, vitamin C and ratio of polyunsaturated to saturated fat, and lower
intakes of saturated fat than the nonvegetarians (n=22). However, of possible
significance to strength sports, protein, zinc and copper intakes were
significantly lower in the vegetarians. Proulx
sounded a note of caution in that the type of vegetarianism also needs to be considered.
For example, a lacto-ovo-vegetarian diet might be expected to provide more
protein, calcium and phosphorous than a vegan diet. However, in the study previously described,
Janelle and Barr (1995) found no significant differences in levels of intake
for protein or phosphorus between lacto-ovo-vegetarians (n=15) and vegans
(n=8), while calcium intake was significantly lower in vegans. These authors
also noted that there were fewer differences in nutrient intake between the
non-vegetarian women and lacto-ovo-vegetarians than between the
non-vegetarians and vegans. They concluded that the diets of their
non-vegetarian subjects were approximately equivalent to those of the
lacto-ovo-vegetarians, but noticeably different from those of the vegans. Because
the vegan diet is less common than the lacto-ovo-vegetarian diet, and it
appears to be quite different to the non-vegetarian diet in terms of nutrient
intake, this paper investigates possible differences only between
non-vegetarian and lacto-ovo-vegetarian diets in relation to sports
performance (especially strength sports). Consequently, unless otherwise
indicated, in the remainder of this paper the term ‘vegetarian’ refers to people who are lacto-ovo-vegetarians. The
belief that a vegetarian diet can provide adequate nutrition, at least to
fuel endurance running, is supported by the findings of Eisinger et al.
(1994). Vegetarian runners and omnivorous runners taking part in a 1,000-km
race over 20 days had their food provided. The foods were matched so that if
all food was eaten, total energy (18.8 MJ) and percentages of energy derived
from carbohydrate, fat and protein (60:30:10 respectively) would be identical
between diets. Over the period of the study, energy, carbohydrate, fat and
protein intakes did not differ between groups, but vegetarian runners had
higher intakes of dietary fiber and poly-unsaturated fatty acids and a lower
intake of cholesterol than the omnivorous competitors. Estimated vitamin and
mineral intakes were also higher in vegetarian runners, except for sodium
chloride and cobalamin (vitamin B12). Half the competitors in each group
finished the race, and the type of diet was not predictive of finishing time.
Although this study imposed a particular nutritional quality of diet on the
vegetarian competitors—and therefore cannot be said to have been wholly
self-selected—it did illustrate that a well-planned vegetarian diet is not
necessarily associated with reduced endurance performance compared to a
non-vegetarian diet. Body Composition and Fitness of Vegetarians Although
it appears that vegetarian diets can provide adequate overall nutrient intake
for endurance activity, specific components of the diet may have special
importance in strength sports. For example, it is possible that in non-vegetarians,
higher protein intakes, or protein specifically obtained from meat, leads to
greater muscularity. Another possibility is that meat eating may lead to
increased muscular hypertrophy in response to resistance training. Several
groups of researchers have addressed the issue of differences in body
dimensions between vegetarians and omnivores. O’Connell et al. (1989) found
that height of vegetarian children under 10 y was consistently lower than US
reference values. However, Seventh Day Adventist children who had vegetarian
diets did not differ substantially from their omnivorous peers in mean
stature, weight, mid-arm circumference, triceps or biceps skinfold thickness,
and weight-for-height (Tayter & Stanek, (1989). The different findings in
these two studies may derive from the inclusion of vegans in the former but
not the latter study. Hebbelinck
et al. (1999) conducted anthropometric analyses (stature, weight, skinfold
thicknesses), puberty ratings (where appropriate), and physical fitness (handgrip
strength, standing long jump, sit-ups in 30 s, and heart-rate recovery
following a step test) of vegetarian children, adolescents and young adults
in the Netherlands. Compared to reference values… • Vegetarian adolescents were of
significantly lower stature, weight and body mass index, but there were no
differences in stature or weight for the other age groups. • Vegetarian children were of equal
fitness, but vegetarian adolescents scored lower on standing long jump and
30-s sit-ups. • Heart rate of vegetarian
adolescents and young adults recovered substantially faster following the
step test. Hebbelinck
et al. concluded that vegetarian adolescents and young adults performed
better at the cardiorespiratory test, but the vegetarian adolescents scored
lower on the strength and explosive power tests. The
possibility raised by the results of Hibbelinck et al.—that a vegetarian diet
might actually lead to improved endurance performance compared to an
omnivorous diet—was not supported in a review by Nieman (1999), who concluded
that "some concerns have been raised about the nutrient status of
vegetarian athletes, [but] a varied and well-planned vegetarian diet is
compatible with successful athletic endeavor". Nieman conceded that strength athletes
probably need more protein than the US RDA of 0.8 mg/kg. His suggestion was
1.4-1.8 mg/kg, but he stated that even "vegan athletes can achieve
optimal protein intake by careful planning, with an emphasis on protein-rich
plant foods such as legumes, nuts and seeds, and whole-grain products". Nieman
did point out one difference between omnivores and vegetarians of possible
significance to performance in strength and explosive sports: intramuscular
creatine concentration. Creatine in the form of creatine phosphate is a source
of energy in high-intensity exercise.
Depletion of creatine phosphate is a cause of fatigue in repeated
bouts of such exercise, and possibly also in short-term endurance exercise.
Vegetarians generally have less intramuscular creatine than omnivores (Maughan,
1995) because creatine is found only in muscle meat (providing an omnivore
with about 1 g creatine per day), while the body itself produces a similar
amount. Ironically, vegetarians may therefore derive greater benefit than
omnivores from supplementation with creatine, but the benefit would
presumably only make up for any lower level of performance in vegetarians
before supplementation. Does Meat-eating Benefit Strength Athletes? In a
message to the list, Andrew Campbell (Australia) argued that a vegetarian
diet may actually be less nutritious than an omnivorous diet, because
"egg yolk, butter and liver… are a rich source of the fat-soluble
vitamins and minerals, including trace elements that bind to the fat
molecules". With reference to mountain climbing, an activity that would
appear to require both endurance and strength, Campbell suggested that a
possible disadvantage of vegetarian diets is the high carbohydrate content,
which "will cause problems to mountain climbers who have sensitive insulin
balance. Short-chain fatty acids from butter provide energy without creating
insulin swings." However, oxygen availability decreases with increasing
altitude, so one possible advantage of carbohydrate over fat or
protein to mountain climbers is a slightly higher return of energy for each
mole of oxygen consumed. Concern
has also been expressed about a possible effect of high intake of
phytoestrogens (e.g. isoflavones found in soy) on testosterone in male
vegetarians. For example, Weber et al. (2001) found that soy phytoestrogens
induced testosterone reduction in male rats. However, according to Kurzer
(2002), "…recent studies in men consuming soyfoods or supplements
containing 40-70 mg/d of soy isoflavones showed few effects on plasma
hormones...” These data do not support concerns about effects on reproductive
hormones." Campbell
and two other correspondents (Mathew Jordan from the University of Calgary
and Mike Stone of Edinburgh University) were unaware of any vegetarians at
the elite level of weightlifting, despite 30 years experience in Stone’s
case. No-one on the list offered any information about the prevalence of
vegetarianism amongst female vs male strength athletes. Kathryn Russell
(address not provided) argued that a perceived dearth of vegetarian
weightlifters may not reflect a lack of effectiveness of the vegetarian diet
for strength athletes; rather, the cultural/anthropological background of
vegetarians may make them unlikely to take up strength sports. Norrie
Williamson (address not provided) argued that, rather than exerting a true
anabolic effect, meat consumption may induce a placebo effect. That is, a
strength athlete who believes that eating meat improves performance may
receive a psychological boost that disappears if a vegetarian diet is
adopted. Williamson (and many other subscribers) called for controlled
studies on this issue, not more anecdotal evidence. Deborah Shulman suggested
that at least 12 weeks would be needed for studies comparing the effects on
performance at strength sports of nutrient-rich vegetarian diets with those
containing meat. Mike
Stone pointed to evidence that strength-power athletes may need additional
protein, which may be "easier" to obtain from animal sources. He
also mentioned having seen unpublished data "indicating that
testosterone concentration can be influenced by saturated fats in the diet
(i.e., meat)". Russell countered by suggesting that if you remove from
consideration those meat-eaters who also take dietary supplements, the pool
of elite strength athletes might be markedly reduced; that is, the benefit
may be coming from the supplements rather than the meat. David
Driscoll (Australia) conducted a brief review of the literature available
through a website
that provides information for people active in strength training and
bodybuilding. This literature pushes the view that low meat/low saturated
fat/high vegetable protein (e.g., soy) diets are associated with a marked
reduction in testosterone (and, by implication, with reduced strength).
Driscoll was not sure of the scientific quality of the information he found,
and no-one on the list offered an assessment. A more
authoritative source of information is the paper by Campbell et al. (1999),
who conducted a 12-week study to compare the effects of a vegetarian diet
with an omnivorous diet on changes in body composition and skeletal muscle
size in older men (51-69 y) in response to resistance training. There were
substantial benefits for omnivores, who lost 6% fat mass, gained 4% fat-free
mass, and increased Type II fiber area by 9% relative to the
vegetarians. A trend towards higher
total protein intake (self-reported) in the omnivores might explain the
effects, but higher concentration of the anabolic hormone testosterone is
more likely. Campbell et al. did not measure testosterone, but Raben et al.
(1992) found higher testosterone in young men consuming a high-protein,
meat-containing diet compared with those consuming a high-protein, vegetarian
diet. If testosterone is involved, a difference in total protein intake per
se would not account entirely for Campbell et al.'s findings, because Volek
et al. (1997) showed an inverse relationship between protein intake and
testosterone concentration. The
discussion on the mailing list went off on a tangent briefly when Bill Proulx
claimed that many strength sport competitors are poorly informed about
nutrition, while Matthew Jordan and Mike Stone argued that strength athletes,
at least at the elite level, are well informed. Scott Naidus (address not
provided) pointed out that nutrition is not a mature science, and that
nutrient needs are not identical for every population group; in fact they
differ even for individuals within
each group. The existence of a plethora of dietary supplements with purported
ergogenic effects only muddies the waters further. Naidus suggested that
sound nutrition for the athlete is a balancing act between prepared foods and
supplements vs fresh foods, and that this balance may vary from athlete to
athlete. Human Evolution and Dietary Need Fabien
Basset (Université Laval, Québec) introduced an evolutionary perspective,
claiming that our closest relative, the chimpanzee, is largely vegetarian. An
anonymous correspondent challenged this claim by reporting that 25 years of
close study in the wild indicates that chimpanzees may actually have a
preference for meat. However, Deborah Shulman pointed out that gorillas,
which are larger and stronger than chimpanzees, are almost exclusively
vegetarian. The
relevance of the eating habits of either chimpanzees or gorillas to human
performance in strength sports is questionable. As the
anonymous correspondent pointed out, hominids had several million years to
evolve physiology and dietary needs different from those of the other great
apes, so any parallels in eating habits may be coincidental. In this context,
Andrew Campbell argued that the omnivorous diet is apparently the natural
state for people: apart from those populations who embrace particular
religious practices, no group is known to have deliberately avoided meat in
their diet. Citing the impeccable source "educational television",
Stephen Seiler (Agder University College, Norway) argued that, far from being
essential, foods of plant origin may even be "optional extras". His
evidence was a claim that the migrant Mongol people of the Eurasian Steppes
"continue to live long, physically active lives on a diet of horse milk,
blood and meat. They have never eaten fruit and vegetables, as no respectable
Mongolian horseman wishes to be tied to the ground, tending crops." The
claims about Mongol horsemen notwithstanding, all but one population of
indigenous peoples studied to date have derived much, if not most of their
energy from foods of plant origin (Kuhnlein and Turner, 1991). The exception
is the Inuit, who nevertheless eagerly sought the few berries and other
plant-derived foods that were available in the short Arctic growing period. Researchers
of the so-called paleolithic diet are divided over the importance of meat in
providing adequate nutrition to our forebears. Eaton et al. (1997) and
Cordain et al. (2000) argued that, in the absence of dairy and grain foods
(the major sources of energy in the modern western diet), high meat intake
was necessary to obtain adequate total energy. Nestle (1999) and Milton
(2000) did not accept that meat intake was high throughout the paleolithic
era. However, there appears to be general agreement that meat may always have
been a component of the natural diet of Homo
sapiens, but the majority of food eaten (at least in terms of total
weight) was obtained from plants. Bill
Proulx did not accept the relevance of paleolithic diets to performance in
strength sports; proponents of the
paleolithic diet argue almost exclusively for its (supposed) health benefits,
but health and strength are different issues.
Proulx pointed out that taking steroids, mega-dosing with
supplements, and consuming excess protein and fat are all activities that
might be associated with improved performance in strength sports, but this
will usually be at the expense of health. Proulx summarized his argument by
stating that "there is no research supporting the necessity of meat in
an athlete's diet and any such opinions are just that, opinions."
Campbell’s final comment was in the form of a question to Proulx: "can
you cite for me [any] studies showing that elite strength athletes perform
just as well on a long term vegetarian diet?" Some
aspects of the discussion appear (at least to me) to have been resolved: • There are several kinds of
vegetarianism. Each could have a
different effect on strength. • There appears to be a
preponderance of meat-eaters among strength athletes at the elite level. It is unclear whether this preponderance
arose from noticeable benefits of meat consumption, a placebo effect of meat
consumption, the confounding influence of supplement consumption, or some
other cultural effect unrelated to any real benefit to performance. • The diets of gorillas, chimpanzees
and paleolithic humans cannot be relied on to indicate the optimal diet for
health and fitness for people generally, or for athletes in strength sports. • Well-planned vegetarian diets,
particularly those including milk and/or eggs, can provide all essential
nutrients for good health and for a high level of sports performance. • The fact that vegetarian diets are
associated with improved health outcomes compared to omnivorous diets does
not necessarily imply that vegetarian diets are superior for performance in
strength sports or any other strength-dependent activities. • Indeed, in one recent study of
resistance training in older males, omnivores had a bigger gain in muscle
mass than vegetarians. • If meat consumption does enhance
strength, the mechanism could be increased testosterone synthesis (possibly
through intake of saturated fat) or increased storage of creatine phosphate
in muscle. • More research is required! Campbell WW, Barton ML Jr, Cyr-Campbell
D, Davey SL, Beard JL, Parise G, Evans WJ (1999). Effects of an omnivorous
diet compared with a lactoovovegetarian diet on resistance-training-induced
changes in body composition and skeletal muscle in older men. American
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L, Brand Miller J, Eaton SB, Mann N, Holt SHA, Speth JD (2000). Plant-animal
subsistence ratios and macronutrient energy estimations in worldwide
hunter-gatherer diets. American Journal of Clinical Nutrition 71, 682-92 Eaton SB,
Eaton SB, Konner, MJ (1997). Paleolithic nutrition revisited: A twelve-year
retrospective on its nature and implications. European Journal of Clinical
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M, Plath M, Jung K, Leitzmann C (1994). Nutrient intake of endurance runners with
ovo-lacto-vegetarian diet and regular western diet. Zeitschrift fur
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M, Clarys P, Malsche A de (1999). Growth, development, and physical fitness
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KC, Barr SI (1995). Nutrient intakes and eating behavior scores of vegetarian
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