Supplements
for Athletes — Safe? Effective?
Today’s Dietitian
By Marie Dunford, PhD, RD
Vol. 7, No. 3, p. 24
No topic generates more controversy among dietitians
than dietary supplements. Two dietitians can read the same research
and draw different conclusions, since the results are often mixed
and inconclusive. Personal biases and philosophical differences
abound; sometimes battle lines are drawn.
Discussing dietary supplements with athletes is
particularly difficult, since there are many commercial promotions
and anecdotal reports in circulation and athletes often engage in
wishful thinking about getting the competitive edge in performance.
Unless precise terms are defined and used, miscommunication can
occur. This article will address the issues facing dietitians, define
terminology, review the evidence for safety and effectiveness, and
make reasonable assertions about several supplements commonly used
by athletes.
Definition of Terms
In the United States, since the passage of the Dietary Supplement
Health and Education Act (DSHEA) in 1994, a dietary supplement is
legally defined as “a vitamin, mineral, herb, botanical, amino
acid, metabolite, constituent, extract, or a combination of any
of these ingredients.”1
The term supplement may describe anything added
to the diet, such as sports beverages, bars, and liquid meal replacements.
Another common term is ergogenic aid, often defined as any substance
or strategy that improves athletic performance by improving the
production of energy. Some dietary supplements are ergogenic—for
example, creatine—but the enhancement is not dramatic. Many
times, ergogenic aid refers not to supplements but to drugs or procedures,
such as amphetamines, bicarbonate loading, or blood doping.
Supplement Use in Athletes
Determining the amount and types of dietary supplements used by
athletes is difficult because the legal and working definitions
of a supplement are so broad. When athletes are asked whether they
take supplements, 85% to 90% say they do, but some may be including
fluid replacement drinks in their responses.2,3 Surveys of athletes
show that nearly one-half take multivitamin and mineral supplements.
Protein supplements (including shakes and bars), creatine, and vitamin
C are also frequently reported.2,3,4 Herbal supplements are used
less often. One study of college athletes found that 17% used herbal
or botanical supplements.4 When discussing dietary supplement use
by athletes, know how supplement is defined and the ingredients
contained.
In general, athletes consume supplements to improve
health or prevent illness, improve performance, or change body composition.2,3,4
Supplement use philosophies of athletes and sports medicine practitioners
often differ. Physicians and dietitians are trained to focus on
both safety and effectiveness—an unsafe (but effective) substance
is not acceptable and a safe (but ineffective) supplement is suspect.
While most athletes care about safety, some are so focused on improving
performance that they sacrifice a degree of safety and act on the
hope that a supplement will be effective. In their minds, winning
and the potential rewards of fame, fortune, and status are worth
a degree of risk.
With such differences in philosophy, it is easy
to understand why there are disagreements and controversies about
the use of dietary supplements. Honest discussions about the athlete’s
goals and knowledge of evidence-based information about safety and
effectiveness are necessary if practitioners are to have credibility
with athletes.5
The decision to take a dietary supplement should
not be made on a whim. Dietitians can provide valuable information
about supplements and any safety concerns should be expressed. But
ultimately, the athlete must decide whether to consume a dietary
supplement and, if so, how much.
Risks vs. Benefits
In considering any dietary supplement, the athlete must calculate
the risk-to-benefit ratio. The first question should be, “Is
it safe?” Many dietary supplements are thought to be safe,
although their long-term safety may not be known due to lack of
data—which calls into question the meaning of the term safe.
Since nothing is entirely safe, the question becomes, “Is
it safe enough?”—in other words, “Is the risk
at an acceptable level?” A dietary supplement may be considered
safe, but that does not mean that it is without side effects. For
example, caffeine is considered safe even though its use may increase
blood pressure and heart rate.
It is also important to note that under present
regulations, dietary supplement manufacturers or distributors are
not required to record or inform the FDA of any reports of illness
or injury associated with the dietary supplements they manufacture
or distribute, so there may be unknown or hidden evidence of dangerous
side effects.
The benefit part of the equation requires us to
ask, “Is it effective?” The answer may depend on the
goal. For example, vitamin C supplements may be effective for decreasing
the severity of a cold6 or protecting against oxidative stress in
endurance athletes,7 but not for improving performance. Protein
supplementation by resistance-trained athletes does not increase
lean mass or strength,8 but since protein supplements are no more
or less effective than food proteins, the athlete may choose them
due to personal preference or convenience. In many cases, effectiveness
is not known, study results are mixed, or human studies are lacking.
Frequently, this question cannot be answered with a definitive yes
or no.
Dietary supplements are not regulated in the same
way as over-the-counter medications or prescription drugs, and potency
and contamination with banned substances are critical issues. In
2000, Gurley et al tested 20 products containing ephedrine alkaloids
and found that the amount of the compound in one-half of them varied
by more than 20% from the stated amounts on their labels.9 Dietary
supplements may contain banned substances, either intentionally
(to increase effectiveness) or unintentionally (through poor quality
control by the manufacturer), and the athlete will face the consequences
of testing positive.10
Consumption of dietary supplements containing prohormones,
precursors to testosterone and other sex-related steroids, poses
a risk for testing positive for banned substances. In 2001, Kamber
et al purchased 75 different dietary supplements via the Internet.11
Each was analyzed to determine whether anabolic steroids or stimulants
were present. The supplements were also tested to determine whether
the compounds present in the supplement were listed on the label.
Seven of the 17 prohormone products tested contained different substances
than indicated on the label, including testosterone. Green and colleagues
purchased 12 brands of over-the-counter steroids, including one
that contained 10 milligrams of testosterone.12 Interestingly, 11
of the 12 contained less than the amount stated on the label. These
and other studies raise serious questions about the potency and
purity of dietary supplements marketed to athletes.
The American Dietetic Association, in its position
paper on food fortification and dietary supplements, states, “Dietetics
professionals should base recommendations for use of fortified foods
or supplements on individual assessment and sound scientific evidence
of efficacy and safety.”13 The most conclusive evidence comes
from prospective, randomized, double-blind, placebo-controlled supplement
trials. The results of such studies should be given greater weight
than results from other study designs. But even the best-designed
study cannot stand alone. Reproducible results are an important
part of the scientific process.
Unfortunately, there is a small body of sound scientific
evidence for many supplements and a lack of long-term studies in
humans. In some cases, evidence is limited to animal or in vitro
studies. When human studies exist, most have been done in small
populations and many lack the statistical power to determine whether
small differences in the performance of well-trained athletes could
be attributed to the supplement. Many studies are conducted under
laboratory conditions, not field conditions, and a supplement that
shows promise in the laboratory may not actually enhance performance.
Also, most subjects are adults and the study results should not
be extrapolated to adolescents or children.
Despite these problems, dietitians must use what
is currently known to educate and counsel athletes.
Strong Evidence of Safety and
Effectiveness
Creatine and caffeine have strong evidence of safety and effectiveness
in athletes. Creatine is one of the best-studied compounds, with
hundreds of research studies published, reviewed, and meta-analyzed.8,14,15
Research studies suggest that creatine is safe.
The lay press has reported that creatine supplementation causes
dehydration, but there is no scientific evidence to support this
assertion. One study of college football players found no adverse
effect on kidney or liver function—on average, the study’s
participants had used creatine for almost three years.16
Many studies have shown that short-term creatine
supplementation results in a small but statistically significant
increase in lean body mass with repeated high-intensity exercise
of less than 30 seconds. This indicates that the creatine supplement
may help athletes maintain or sustain force output for a longer
period of time, thus completing more repetitions of an exercise.
Most studies show an ergogenic effect for athletes in a variety
of high-intensity, short-duration sports—but a performance
effect has only been shown in weight lifters.15 The weight gain
that is typical of creatine supplementation may be detrimental to
some athletes.
Caffeine is effective because it is a central nervous
system stimulant and its use results in an increased sense of awareness
and a decreased perception of effort. It does not significantly
increase fat oxidation or spare muscle glycogen in endurance athletes,17
cause dehydration,18 or have a significant effect on fat/weight
loss.19 Caffeine is considered safe although there are known side
effects. These side effects include an increased blood pressure
at rest and during exercise, increased heart rate, gastrointestinal
distress, and insomnia.18
Evidence of Safety, but
Effectiveness Not Established
Glutamine, branched chain amino acids (BCAAs), and conjugated linoleic
acid (CLA) are examples of supplements that appear to be safe but
whose effectiveness has not been firmly established.
Under normal conditions, glutamine is a nonessential
amino acid, but under physiological stress, it is considered conditionally
essential because it is a source of fuel for immune system cells.
Studies have shown that plasma glutamine is decreased after strenuous
exercise in endurance athletes. However, study results are mixed
about the benefits of glutamine supplementation. Castell reported
a decrease in the number of infections in endurance athletes,20
but others did not find that supplemental glutamine offset immunodepression.21,22
Bassitt et al concluded that BCAAs, which are metabolized
to glutamine in skeletal muscle, have a positive effect on endurance
athletes’ immune systems.23,24 The study populations have
been small. For example, one study involved 12 elite male triathletes.23
These supplements appear to be safe and show promise, but more research
is needed.
CLA is an isomer of linoleic acid. Most research
studies in humans use 3 to 4 grams of CLA daily, taken in three
divided doses with meals over four to eight weeks. These doses appear
to be safe for short-term use, but the long-term safety is unknown.
Animal studies have reported a decrease in body fat, an increase
in lean mass, and improved lipoprotein metabolism. Some human studies
have also reported these results. The effect of CLA on humans is
probably less than the effect on animals. While the animal studies
show promise, the effectiveness in humans is not well-established.25,26
When safety can be reasonably assumed but effectiveness
is not as clear, some athletes adopt a “won’t hurt,
might help” attitude. Ineffective supplements can be a waste
of money because they don’t produce the desired effect, but
some athletes are willing to “give it a try.” Particularly
troublesome are those supplements that have questionable safety
and effectiveness profiles.
Questionable or Unknown Safety and Effectiveness
Dehydroepiandrosterone (DHEA) is a prohormone, a precursor to testosterone
and estrogen. It is weaker than other prohormones such as androstenedione
and androstenediol. DHEA is popular among strength athletes who
hope it will elevate blood testosterone levels and increase muscle
mass. Among older people, including athletes, DHEA supplements are
used to reverse low DHEA concentrations associated with age.
Studies have not shown that DHEA supplements have
an anabolic effect or improve athletic performance.27 This is not
surprising because the biochemical conversion of cholesterol to
testosterone via DHEA is not the primary conversion pathway. It
is well-known that DHEA levels decline steeply with age, probably
due to a decrease in the number of cells that produce it. The biological
significance of this decline is not entirely known. Supplementation
in older adults does raise the concentration of DHEA in the blood,
but the effect is unknown because of a lack of well-controlled clinical
studies.28 Further studies are needed to determine whether DHEA
is a “fountain of youth.”
DHEA is a prescription drug in most countries due
to its potential for abuse. It was also a prescription drug in the
United States prior to the passage of the DSHEA. It is now classified
as a dietary supplement. The safety profile associated with high
doses or long-term use is unknown.27,28
Chromium picolinate is a supplement marketed to
athletes who wish to decrease body fat and increase muscle mass.
The suggested mechanisms are an increase in metabolic rate and enhanced
insulin sensitivity, which promotes protein synthesis.29,30 A meta-analysis
of 10 studies showed that weight loss was small (approximately 1
kilogram) and not clinically meaningful.30 Increases in lean mass,
suggested in early studies, have not been replicated in more recent
studies with stricter methodology.29
The safety concern relates to the use of picolinate,
which provides great stability to the compound and results in a
much higher absorption of chromium than would be expected from food.29,31
Other forms, such as chromium chloride supplements, appear to be
safe when taken in 50- to 200-microgram doses daily. Higher intakes
may decrease iron absorption and excess chromium in the body can
damage DNA.32
FDA Actions
The passage of the DSHEA resulted in a freewheeling atmosphere and
sharply increased sales of dietary supplements. Some experts believed
that certain products should never have been categorized as dietary
supplements and a predictable backlash occurred once some adverse
consequences were reported. The deaths of two high-profile athletes
brought national attention to dietary supplement use. The FDA has
taken regulatory action against two dietary supplements that were
popular with some athletes: androstenedione and ephedrine (one of
the ephedrine alkaloids).
In March 2004, the FDA released a white paper that
listed more than 25 potential androgenic and estrogenic effects
of androstenedione and related compounds.33 These effects include
reduction in high-density lipoprotein cholesterol and testicular
atrophy. The paper notes that children and adolescents are particularly
vulnerable since some of the effects (eg, disruption of normal sexual
development) are irreversible. The FDA sent letters to manufacturers,
marketers, and distributors of androstenedione-containing dietary
supplements asking them to stop distribution on the basis that such
supplements are adulterated. Most sports governing bodies list androstenedione
as a banned substance.
In April 2004, the FDA banned the sale of dietary
supplements containing ephedrine alkaloids on the basis that these
supplements have an unreasonable risk of illness or injury.34,35
Experts have long argued over the safety of ephedrine alkaloids,
particularly the dosage considered safe.36,37 Studies of the effectiveness
of ephedrine and caffeine as a performance enhancer have been mixed.35
The FDA has also issued documents that provide guidance
for itself, the dietary supplement industry, and nutrition professionals.
These documents are nonbinding recommendations. The Interim Evidence-based
Ranking System for Scientific Data describes a process to rank the
scientific evidence based on the quality and quantity of research
to support qualified health claims on the labels of dietary supplements.38
A second document suggests ways for manufacturers to substantiate
label claims so they are truthful and not misleading.39 These documents
explain and give examples of factors that affect the quality of
scientific research and the resulting strength of the evidence.
The AIS Supplement Program
The Australian Institute of Sport (AIS) developed an evidence-based
ranking system to help athletes make wise supplement decisions.40
The program, which is updated yearly, uses A, B, C, and D classifications.
Group A supplements have scientific evidence of safety and effectiveness.
This category currently includes products such as creatine, iron,
calcium, antioxidants, and caffeine (under certain circumstances).
Group B supplements are provided to athletes only if they are involved
in a current research study. Examples include colostrum, glutamine,
hydroxy-methyl-butyrate, and ribose. These supplements show some
promise but lack the scientific evidence required for group A. The
goal for group B supplements is to collect enough data to move the
supplement either into group A or C.
Group C includes supplements that lack proof of
effectiveness, such as bee pollen, carnitine, and oral vitamin B12.
The AIS notes that group C includes the majority of supplements
marketed to athletes. Also included in this category are “all
network marketing supplements.” The companies named use multilevel
marketing to sell dietary supplements. Members of group D are supplements
that have been banned by sports governing bodies or represent a
high risk for testing positive for banned substances. More information
can be found at www.ais.org.au/nutrition/suppprogram.asp.
Because the area of dietary supplements will never
be static, dietitians must constantly add to their knowledge. Not
only must they read and evaluate new information, but they must
also place the new information in the context of what is already
known. The promise shown in early studies may be confirmed, as was
the case with creatine, or not supported, as is the case with chromium
picolinate supplements and body composition changes. Supplements
that lack evidence of effectiveness today may not always lack that
evidence. As more controlled clinical studies are published, our
current theories are likely to be refined or revised. Chart 1 lists
some excellent government sources of information on supplements,
which helps dietitians to keep abreast of both research and regulations.
None of us are without bias, and perhaps the hardest
studies to evaluate are those that challenge our personal philosophy
on supplementation or our currently held beliefs about a particular
supplement. Personal usage or nonusage may influence professional
recommendations. Dietitians must provide evidence-based information
so athletes can assess the risks and benefits of taking dietary
supplements to meet their performance and health goals. Honest discussions
and open-minded skepticism are vital.
— Marie Dunford, PhD, RD, is the author
of a consumer-oriented nutrition book, Nutrition Logic: Food First,
Supplements Second, and the editor of a forthcoming book for professionals,
Sports Nutrition: A Practice Manual for Professionals.
References
1. Food and Drug Administration. Dietary Supplement Health and Education
Act of 1994. Available at: http://www.cfsan.fda.gov/~dms/dietsupp.html.
Accessed December 29, 2004.
2. Morrison LJ, Gizis F, Shorter B. Prevalent use
of dietary supplements among people who exercise at a commercial
gym. Int J Sport Nutr Exerc Metab. 2004;14(4):481-492.
3. Froiland K, Koszewski W, Hingst J, Kopecky L.
Nutritional supplement use among college athletes and their sources
of information. Int J Sport Nutr Exerc Metab.2004;14(1):104-120.
4. Herbold NH, Visconti BK, Frates S, Bandini L.
Traditional and nontraditional supplement use by collegiate female
varsity athletes. Int J Sport Nutr Exerc Metab. 2004;14(5):586-593.
5. Schwenk TL, Costley CD. When food becomes a drug:
Nonanabolic nutritional supplement use in athletes. Am J Sports
Med. 2002;30(6):907-916.
6. Douglas RM, Chalker EB, Treacy B. Vitamin C for
preventing and treating the common cold. Cochrane Database
Syst Rev. 2000;(2):CD000980.
7. Evans WJ. Vitamin E, vitamin C, and exercise.
Am J Clin Nutr. 2000;72(suppl):647S-652S.
8. Nissen SL, Sharp RL. Effect of dietary supplements
on lean mass and strength gains with resistance exercise: A meta-analysis.
J Appl Physiol. 2003;94(2):651-659.
9. Gurley BJ, Gardner SF, Hubbard MA. Content versus
label claims in ephedra-containing dietary supplements. Am
J Health Syst Pharm. 2000;15;57(10):963-969.
10. Maughan R. Contamination of supplements: An
interview with professor Ron Maughan by Louise M. Burke. Int
J Sport Nutr Exerc Metab. 2004;14(4):493.
11. Kamber M, Baume N, Saugy M, Rivier L. Nutrition
supplements as a source for positive doping cases? Int J Sport
Nutr Exerc Metab. 2001;11(2):258-263.
12. Green GA, Catlin DH, Starcevic B. Analysis of
over-the-counter dietary supplements. Clin J Sports Med.
2001;11(4):254-259.
13. The American Dietetic Association. Position
of the American Dietetic Association: Food fortification and dietary
supplements. J Am Diet Assoc. 2001;101(1):115-125.
14. Branch JD. Effect of creatine supplementation
on body composition and performance: A meta-analysis. Int
J Sport Nutr Exerc Metab. 2003;13(2):198-226.
15. Volek JS, Rawson ES. Scientific basis and practical
aspects of creatine supplementation for athletes. Nutrition.
2004;20(7-8):609-614.
16. Mayhew DL, Mayhew JL, Ware JS. Effects of long-term
creatine supplementation on liver and kidney functions in American
college football players. Int J Sport Nutr Exerc Metab. 2002;12(4):453-460.
17. Paluska SA. Caffeine and exercise. Curr
Sports Med Rep. 2003;2(4):213-219.
18. Armstrong LE. Caffeine, body fluid-electrolyte
balance, and exercise performance. Int J Sport Nutr Exerc
Metab. 2002;12(2):189-206.
19. Graham TE. Caffeine, coffee and ephedrine: Impact
on exercise performance and metabolism. Can J Appl Physiol.
2001;26(suppl):S103-S119.
20. Castell LM. Can glutamine modify the apparent
immunodepression observed after prolonged, exhaustive exercise?
Nutrition. 2002;18(5):371-375.
21. Nieman DC. Exercise immunology: Nutritional
countermeasures. Can J Appl Physiol. 2001;26(suppl):S45-S55.
22. Hiscock N, Pedersen BK. Exercise-induced immunodepression-plasma
glutamine is not the link. J Appl Physiol. 2002;93(3):813-822.
23. Bassit RA, Swada LA, Bacurau RF, et al. The
effect of BCAA supplementation upon the immune response of triathletes.
Med Sci Sports Exerc. 2000;32(7):1214-1219.
24. Bassit RA, Swada LA, Bacurau RF, et al. Branched-chain
amino acid supplementation and the immune response of long-distance
athletes. Nutrition. 2002;18(5):376-379.
25. Terpstra AH. Effect of conjugated linoleic acid
on body composition and plasma lipids in humans: An overview of
the literature. Am J Clin Nutr. 2004:79(3):352-361.
26. Rainer L, Heiss CJ. Conjugated linoleic acid:
Health implications and effects on body composition. J Am Diet
Assoc. 2004;104(6):963-968.
27. Corrigan B. DHEA and sport. Clin J Sport
Med. 2002;12(4):236-241.
28. Hornsby PJ. DHEA: A biologist’s perspective.
J Am Geriat Soc. 1997;45(11):1395-1401.
29. Vincent JB. The potential value and toxicity
of chromium picolinate as a nutritional supplement, weight loss
agent and muscle development agent. Sports Med. 2003;33:213-230.
30. Pittler MH, Stevinson C, Ernst E. Chromium picolinate
for reducing body weight: Meta-analysis of randomized trials. Int
J Obes Relat Metab Disord. 2003;27(4):522-529.
31. Vincent J. The biochemistry of chromium. J
Nutr. 2000;130(4):715-718.
32. Lusaki HC. Magnesium, zinc, and chromium nutriture
and physical activity. Am J Clin Nutr. 2000;72(2 suppl):585S-593S.
33. Food and Drug Administration. FDA White Paper:
Health Effects of Androstenedione. Released March 11, 2004. Available
at: http://www.fda.gov/oc/whitepapers/andro.html.
Accessed December 29, 2004.
34. Food and Drug Administration. 2004. Dietary
Supplements Containing Ephedrine Alkaloids Final Rule Summary. Available
at: http://www.fda.gov/oc/initiatives/ephedra/february2004/finalsummary.html.
Accessed December 29, 2004.
35. Shekelle PG, Hardy ML, Morton SC, et al. Efficacy
and safety of ephedra and ephedrine for weight loss and athletic
performance: A meta-analysis. JAMA. 2003;289(12):1537-1545.
36. Food and Drug Administration. 2000. Safety of
Dietary Supplements Containing Ephedrine Alkaloids. Transcript of
a public meeting held August 8-9, 2000. Available at: http://www.fda.gov.
Accessed December 29, 2004.
37. CANTOX Health Services International. Safety
Assessment and Determination of a Tolerable Upper Limit of Ephedra.
2000. Available at: http://www.crnusa.org.
Accessed December 29, 2004.
38. Food and Drug Administration. July 2003. Interim
Evidence-based Ranking System for Scientific Data. Available at:
http://www.cfsan.fda.gov/guidance.html.
Accessed December 29, 2004.
39. Food and Drug Administration. November 2004.
Substantiation for Dietary Supplement Claims Made Under Section
403(r) (6) of the Federal Food, Drug, and Cosmetic Act. Available
at: http://www.cfsan.fda.gov/guidance.html.
Accessed December 29, 2004.
40. Australian Institute of Sport. Sports Supplement
Program. Available at: http://www.ais.org.au/nutrition/suppprogram.asp
Government Sources of Information on Dietary
Supplements
National Institutes of Health, Office of Dietary
Supplements
International Bibliographic Information on Dietary Supplements Database
http://ods.od.nih.gov/health_
information/ibids.aspx
Users can search citations and abstracts from published scientific
literature, including international journals. Searches can be limited
to peer-reviewed citations.
USDA, Food and Nutrition Information Center
Dietary Supplements and Herbal Information
www.nal.usda.gov/fnic/etext/000015.html
This Web site includes many links to general dietary supplement
information, as well as regulatory information and consumer-oriented
material about dietary supplements, ergogenic aids, and alternative
medicine.
FDA, Center for Food Safety and Applied Nutrition
www.cfsan.fda.gov/list.html
Easy access to FDA regulatory and guidance documents and abundant
information about dietary supplements
National Library of Medicine, PubMed
www.ncbi.nlm.nih.gov/entrez/query.fcgi
PubMed has more than 15 million citations for biomedical articles.
Includes links to full text articles, some of which are available
for free and most of which are available for purchase. Searches
may be limited by publication type, such as review articles, meta-analyses,
clinical trials, or randomized controlled trials.
Examination
1. According to published surveys, what percentage of athletes claim
to take supplements?
a. 10% to 15%
b. 20% to 25%
c. approximately 50%
d. 60% to 75%
e. 85% to 90%
2. Which two dietary supplements have strong evidence
of safety and effectiveness?
a. androstenedione and dehydroepiandrosterone (DHEA)
b. branched chain amino acids (BCAAs) and glutamine
c. creatine and caffeine
d. chromium picolinate and caffeine
e. none of the above
3. Which dietary supplements have the FDA taken
regulatory action against?
a. androstenedione and DHEA
b. androstenedione and ephedrine alkaloids
c. DHEA and chromium picolinate
d. all of the above
e. none of the above
4. The American Dietetic Association suggests that
recommendations for supplementation should be based on the:
a. experience of the practitioner
b. number of human studies published
c. extent to which studies have been meta-analyzed
d. evidence for safety and effectiveness
e. number of adverse events reported to the FDA
5. You are counseling an athlete who is taking creatine.
How do you respond to his question, “Do creatine supplements
cause dehydration?”
a. There is no scientific evidence that shows creatine supplements
cause dehydration.
b. There is some scientific evidence and there are many reports
by athletes connecting creatine supplements and dehydration.
c. The scientific evidence is mixed, but the most recent studies
show a link between creatine supplements and dehydration.
d. The scientific evidence strongly supports that creatine supplements
cause dehydration.
e. Everyone knows that creatine supplements cause dehydration, so
this is one case where you can’t depend on the scientific
evidence.
6. Caffeine is considered effective because:
a. fat oxidation is increased
b. muscle glycogen is spared
c. total body weight is lost
d. body fat and body weight are lost
e. awareness is increased and perceived effort is decreased
7. Supplemental glutamine and BCAA are being studied
in endurance athletes to determine
effectiveness in which body system?
a. cardiovascular system
b. cardiopulmonary system
c. renal system
d. immune system
e. none of the above
8. Which of the following is sold as a prescription
drug in most countries but is sold as a dietary supplement in the
United States?
a. BCAA
b. conjugated linoleic acid (CLA)
c. DHEA
d. chromium picolinate
e. none of the above
9. Which of the following dietary supplements has
shown promise in animal studies but lacks conclusive evidence in
humans?
a. glutamine
b. CLA
c. creatine
d. caffeine
e. none of the above
10. The risks and benefits of taking a dietary supplement
should accrue to the:
a. physician
b. dietitian
c. athlete
d. manufacturer
e. FDA
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