|
Perspectives: Nutrition |
|
Effect of
Vegetarian Diets on Performance in Strength Sports
Chris
Forbes-Ewan
Sportscience
6, sportsci.org/jour/0201/cf-e.htm, 2002 (3479 words)
Defence Nutrition Research Centre, Defence Science and Technology Organisation,
Scottsdale, Tasmania 7260, Australia. Email. Reviewed by Greg Cox, Sports Nutrition,
Australian Institute of Sport, Canberra, Australia 2616
|
A lacto-ovovegetarian diet can provide all the nutrients required for optimal health. Anecdotal reports suggest that many successful endurance athletes are vegetarians whereas few reports suggest that elite strength athletes follow a vegetarian diet. Strength and power athletes almost invariably include meat in their diets, although it is unclear whether the benefits of meat consumption for strength and power are real or imagined. KEYWORDS: nutrition, resistance training. Reprint pdf · Reprint doc |
Arguments in Favor
of the Vegetarian Diet
Body Composition
and Fitness of Vegetarians
Does Meat-eating
Benefit Strength Athletes?
Human Evolution
and Dietary Need
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 Journal of Clinical Nutrition 70, 1032-1039
Cordain 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
Nutrition 51, 207-216
Eisinger M,
Plath M, Jung K, Leitzmann C (1994). Nutrient intake of endurance runners with
ovo-lacto-vegetarian diet and regular western diet. Zeitschrift fur
Ernahrungswiss 33, 217-229
Hebbelinck
M, Clarys P, Malsche A de (1999). Growth, development, and physical fitness of
Flemish vegetarian children, adolescents, and young adults. American Journal of
Clinical Nutrition 70, 579S-585S
Janelle KC,
Barr SI (1995). Nutrient intakes and eating behavior scores of vegetarian and
nonvegetarian women. Journal of the American Dietetic Association 95, 180-186
Kuhnlein
HV, Turner NJ (1991). Traditional Plant Foods of Canadian Indigenous Peoples:
Nutrition, Botany and Use. Philadelphia, PA: Gordon & Breach Science
Publishers.
Kurzer MS
(2002). Hormonal effects of soy in premenopausal women and men. Journal of
Nutrition 132, 570S-573S
Maughan RJ
(1995) Creatine supplementation and exercise performance. International Journal
of Sports Nutrition 5, S39-S61
Milton K
(2000). Hunter-gatherer diets—a different perspective. American Journal of
Clinical Nutrition 71, 665-667
Nieman DC
(1999). Physical fitness and vegetarian diets: is there a relation? American
Journal of Clinical Nutrition 70, 570S-575S
O’Connell
JM, Dibley MJ, Wallace B, Mares JS, Yip R (1989). Growth of vegetarian
children: the Farm Study. Pediatrics 84, 475-481
Raben A,
Kiens B, Richter EA, Rasmussen LB, Svenstrup B, Micic S, Bennett P (1992). Serum sex hormones and endurance
performance after a lacto-ovovegetarian and a mixed diet. Medicine &
Science in Sports & Exercise 24, 1290-1297
Taytor M,
Stanek KL (1989). Anthropometric and dietary assessment of omnivore and
lacto-ovo-vegetarian children. Journal of the American Dietetic Association 89,
1661-1663
Volek JS,
Kraemer WJ, Bush JA, Incledon T, Boetes M (1997). Testosterone and cortisol in
relationship to dietary nutrients and resistance exercise. Journal of Applied
Physiology 82, 49-54
Weber KS,
Setchell KD, Stocco DM, Lephart ED (2001). Dietary soy-phytoestrogens decrease
testosterone levels and prostate weight without altering LH, prostate
5alpha-reductase or testicular steroidogenic acute regulatory peptide levels in
adult male Sprague-Dawley rats. Journal of Endocrinology 170, 591-599
Published June 2002
Updated July 9 2002
editor
©2002