Sports Nutrition Products

Chapter 40
Sports Nutrition Products
ROBERT MURRAY
Introduction
In the never-ending quest to improve performance, athletes and coaches are quick to embrace
almost any notion that promises quick success.
New ideas involving sports equipment, training techniques and nutritional interventions are
often greeted enthusiastically, put into practice
before ample testing has occurred, and touted
anecdotally as the latest and greatest idea to hit
the sporting world. While most scientists would
advise a more cautious approach to integrating
new ideas into an athlete’s training regimen, the
fact of the matter is that coaches and athletes
have always been and will always be the initial
arbiters of proposed innovations. More often
than not, in the time required for adequate
scientific evaluation, the idea has already been
superceded by the next ‘improvement’. This is
particularly so in the area of sports nutrition,
where there has historically been a rapid and
seemingly endless series of product introductions, some of which make remarkable claims for
superior performance.
Confronted with a constantly changing array
of sports nutrition products, the claims for which
can appear to bear convincing scientific support,
it is not surprising that athletes and coaches have
difficulty determining which claims are valid.
Considering that it often requires sports scientists considerable time in the laboratory to separate fact from fiction when it comes to claims for
sports nutrition products, it is entirely understandable that coaches and athletes find it impos-
sible to do the same. This confusion has resulted
from the plethora of commercial products targeted at physically active people, from the inability of government agencies to adequately
regulate the claims made for such products, from
the rapid turnover of sports nutrition products
in the marketplace, and from the confusion resulting from the misuse of scientific claims.
Although there is little doubt that some sports
nutrition products provide demonstrable benefits when properly used, the claims for other
products and nutritional interventions are often
dubious, ill-founded, unproven, or abysmally
deficient of scientific merit.
For the purpose of this chapter, sports nutrition products and sports nutrition supplements
will be considered to be synonymous, as virtually all sports nutrition supplements are available as commercial products. Whereas it is
relatively easy to identify a sports nutrition
product by virtue of the advertising claims made
for it, it is more difficult to gain agreement on
what constitutes a sports nutrition supplement.
What is a sports nutrition
supplement?
There is no consensus opinion on the definition
of a sports nutrition supplement. In the strictest
sense, sport nutritional supplements might be
defined as products that include only those
macro- or micronutrients included in dietary
guidelines such as the US National Research
Council’s recommended dietary allowances
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practical issues
(National Research Council 1989). In other
words, the composition of a sports nutrition supplement would be limited to water, carbohydrate, fat, protein and amino acids, vitamins and
minerals. This definition would exclude a wide
variety of nutritional supplements already on the
market (e.g. creatine, carnitine, vanadyl sulphate, lipoic acid, etc.). In this case, such a strict
definition is both unwieldly and unrealistic.
In the broadest sense, sports nutrition supplements could include any food, beverage, tablet,
gel, concentrate, powder or potion purported to
be of some value to physically active people.
Both the value and the limitation of adopting a
broad definition of what might constitute a sport
nutrition supplement is that the definition is not
exclusionary. In this context, everything from
aspirin to zinc could be considered a sport
nutrition supplement. In addition, one is left to
wrestle with ticklish questions such as whether
the effect of the ingested substance is nutritional,
physiological or pharmacological.
In the United States, the Dietary Supplement
Health Education Act of 1994 established a definition for dietary supplements that included the
following wording: ‘dietary supplement means a
product . . . intended to supplement the diet that
. . . contains one or more of the following dietary
ingredients: a vitamin; a mineral; an herb or
other botanical; an amino acid . . . a concentrate,
metabolite, constituent, extract’. In the 1994 Act,
it is estimated that 4000 such products are currently marketed in the US. Although this description includes many products positioned as
sports nutrition supplements, it excludes foods
and beverages formulated for use by physically
active people.
For the purpose of this chapter, it is necessary
to accept a broad definition, complete with its
attendant limitations, to allow for discussion of
the wide range of products that are marketed for
use by physically active people. A sport nutrition
product/supplement is any food, beverage, tablet, gel,
concentrate, powder, capsule, gelcap, geltab or liquid
droplet purported to affect body structure, function or
nutritional status in such a way as to be of value
to physically active people. To narrow the scope of
discussion, it is necessary to exclude alcohol,
analgesics, caffeine, amphetamines, anabolic
steroids, hormones, b-blockers, diuretics and
other pharmacological substances that may affect
structure and function but are not considered
nutrients.
Objectives of nutritional
supplementation
Abiding by the definition above, an efficacious
sports nutrition product is one that provides a
structural, functional and/or nutritional benefit
that is documented by scientific research. For
example, an iron-deficient female runner who
supplements her diet with ferrous sulphate
tablets realizes a functional and nutritional
benefit that was not achieved by her usual diet. A
bodybuilder who is able to gain lean body mass
by ingesting a product that provides energy and
protein enjoys a structural benefit afforded by
that supplement. The cyclist who ingests a highcarbohydrate beverage to help assure adequate
carbohydrate intake benefits from both structural (restoration of muscle and liver glycogen
stores) and functional (rapid recovery, increased
endurance) effects.
From a scientific standpoint, it is possible to
experimentally evaluate the ability of a product
to affect human structure or function. In fact, the
manufacturers of some sports nutrition products
require that rigorous scientific and legal standards be met before a product claim can be made.
Unfortunately, many manufacturers do not.
Evaluating product claims
One only has to page through an issue of any
health- and fitness-related magazine to find
dozens of advertisements and articles on nutritional supplements. For example, the March 1997
US edition of Muscle and Fitness (Weider Publications, Inc.), a popular health and fitness magazine with international distribution, contains
nine separate articles and nearly 50 advertisements on sports nutrition supplements. Product
claims are many and varied, including ‘helps
sports nutrition products
your body use oxygen more efficiently’, ‘help
sculpt a leaner, firmer body’, ‘contains powerful
cell volumizing and recovery nutrients’, ‘the
most effective antioxidant nutrients’, ‘increases
muscle protein synthesis while increasing cell
hydration’, ‘promotes protein synthesis and
glycogen storage, supports immune function
and cell volumizing, and limits catabolism by
cortisol for optimal workout recovery’, ‘increase
levels of adenosine triphosphate’, ‘more leangained mass in less time’, ‘prevents muscle loss
during training and dieting’, ‘improve strength
and stamina during workouts’, ‘increases lean
muscle mass and promotes fat loss’, and
‘increase peak power output, mean body mass,
and muscular performance’. Each of these
product claims involves a structural or functional benefit that is directly testable through scientific experimentation. Although a few of these
advertising claims were accompanied by a scientific reference, the vast majority were not. This
observation is similar to that of Grunewald and
Bailey (1993), who evaluated the advertising
claims for 624 products targeted at bodybuilders.
The products were associated with over 800
performance-related claims, the vast majority of
which were unsubstantiated by scientific
research.
If the stated objective of a sports nutrition supplement is to provide a structural or functional
benefit, validation of the claim can be accomplished in two ways. The highest level of scientific validation for the efficacy of a nutrition
supplement is generated by research published
in peer-reviewed scientific journals. In this
context, the strongest such support is developed
when numerous laboratories report similar findings of product effectiveness. A case in point is
the scientific consensus that has been developed
for carbohydrate–electrolyte beverages on the
basis of more than 100 scientific studies published in peer-reviewed journals. The other
acceptable example of scientific credibility is
when the efficacy of a nutrition supplement can
be established by face validity — that is, when the
claims made for the product are widely recognized as being both truthful and scientifically
525
valid. For example, if a product containing large
amounts of carbohydrate per serving is claimed
to provide a supplemental source of dietary
carbohydrate that helps in glycogen restoration,
the product’s efficacy in that regard enjoys the
benefit of face validity. The product claim is
accepted as true on its face.
Butterfield (1996) and other authors (Burke
1992; Rangachari & Mierson 1995; Sherman &
Lamb 1995; Coleman & Nelson Steen 1996) have
suggested guidelines for evaluating research
results and product claims. Sherman and Lamb
(1995) identified 10 essential characteristics that
should be present in an acceptable experimental
design. These include:
1 use of an appropriate subject population;
2 adequate control of diet and exercise;
3 use of a double-blind design with placebo;
4 random assignment of subjects to treatment
groups;
5 repeated measures or cross-over designs to
reduce the impact of individual differences;
6 inclusion of appropriate familiarization
trials;
7 adequate control of possible mitigating
factors such as environmental conditions and
hydration status;
8 measurement of variables related to the
potential mechanism of effect;
9 an acceptable number of subjects to assure
ample statistical power; and
10 proper statistical analyses.
A critical evaluation of research data requires
a trained and experienced eye. Even the most
sceptical layperson is unprepared to undertake a
thorough review of product claims and related
literature. As a result, it is the responsibility of the
trained sports health professional to be proactive
in providing the public with clear and accurate
guidance regarding the efficacy of products that
claim to provide structural or functional benefits.
The advertisements for some sports nutrition
products rely solely upon claims of nutrient
content rather than structural or functional
claims. The product’s label and advertising
merely make a statement regarding the product’s
nutritional content. Examples of such claims
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practical issues
include ‘contains calcium’, ‘delivers 2200 low-fat
calories per serving’, ‘contains di- and tripeptides’, and ‘provides nine important vitamins
and minerals’. Provided that these claims
conform to the product’s actual content, they are
nothing more than statements of fact.
Ethical considerations regarding
sports nutrition products
The International Olympic Committee’s list of
banned drugs provides a relatively clear-cut, but
by no means uncontroversial, way of identifying
a substance ‘which because of its nature, dosage,
or application is able to boost the athlete’s performance in competition in an artificial and unfair
manner’ (International Olympic Committee
1995). The IOC regulations also state that ‘doping
is the administration of or the use by a competing
athlete of any substance foreign to the body or of
any physiological substance taken in abnormal
quantity or by an abnormal route of entry into
the body, with the intention of increasing in an
artificial and unfair manner his performance in
competition’. The wording of this sentence may
be instructive in the evaluation of the ethical considerations surrounding the use of some nutritional supplements. However, as with the IOC’s
restrictions against doping, a clear understanding of the ethical issues regarding nutritional
supplementation can be hard to come by. For
example, the ingestion of a glucose–electrolyte
solution during exercise involves a normal route
of administration of a normal quantity of nutrients and consequently presents little in the way
of ethical concerns. On the other hand, if a cyclist
were to receive the same nutrients intravenously
while riding in competition, such administration
would surely be considered abnormal and
ethically questionable. Yet, it is quite common
for athletes to receive intravenous glucose–
electrolyte solutions following training and competition under the guise of medical necessity
when the actual intent is to hasten recovery.
In discussing the ethical considerations of
using nutritional ergogenic aids, Williams (1994)
noted that some nutrients given in high doses
can exert pharmacological effects, responses that
would appear to be at odds with the language of
the IOC doping regulations. One such example is
niacin (vitamin B3), high doses of which are commonly prescribed to reduce serum cholesterol
(DiPalma & Thayer 1991), an effect that is clearly
pharmacological. If similarly large doses of a
vitamin improved performance, would this be
considered a pharmacological or nutritional
effect? Similarly, as also noted by Williams
(1994), if research confirms the ergogenic effect of
creatine loading, what are the attendant ethical
considerations? Does the fact that the body normally synthesizes creatine preclude it from being
considered a nutrient? Are the effects of creatine
feeding pharmacological or physiological, rather
than nutritional? Does it matter? These same
questions can surely be applied to any nutrient
ingested in amounts far exceeding the established values of normal nutritional requirements.
Regardless of the murky nature of some issues
involving sports nutrition supplements, the
reality is that thousands of such products are
marketed around the world.
Categories of
sports nutrition products
A variety of authors and organizations have
attempted to categorize sports nutrition products to establish a framework by which the
efficacy of the products can be more easily
evaluated. Three such attempts at categorization
are briefly described below. As with all systems
of categorization, each has its own merits and
limitations.
Burke and Read (1993) suggested a simple
two-category approach that classifies sports
nutrition supplements as either dietary supplements or nutritional ergogenic aids. According to
the authors, dietary supplements provide a convenient and practical means of consuming nutrients to meet the special dietary needs of athletes.
In this regard, the supplement itself does not
directly improve performance, but simply meets
a dietary need. Examples include sports drinks,
high-carbohydrate supplements, liquid meal
sports nutrition products
supplements, and vitamin and mineral supplements. For example, ferrous sulphate tablets
consumed by an iron-deficient female athlete or
a concentrated carbohydrate beverage ingested
following training would be considered dietary
supplements.
Nutritional ergogenic aids encompass those
products whose ingestion is purported to
directly and immediately provoke an improvement in performance. Burke (1992) suggests that
these supplements are better labelled as ‘proposed ergogenic aids’ because there is scant scientific support for their effectiveness. Bee pollen,
ginseng, vanadium, inosine, molybdenum, carnitine and countless other pills, potions and
powders appear to fall neatly into this category.
Upon further examination, however, the distinction between dietary supplements and nutritional ergogenic aids can become blurred. When
carbohydrate is ingested during exercise, is it
meeting a special dietary need or provoking an
immediate improvement in performance? Some
would argue that it does both.
Butterfield (1996) suggested that sports nutrition products could be categorized into four
areas:
1 Metabolic fuels such as carbohydrate, fat and
metabolic intermediates including pyruvate,
lactate and components of the Krebs cycle.
2 Limited cellular components such as creatine,
carnitine, vitamins and free amino acids.
3 Substances with purported anabolic effects
such as energy, protein, chromium and
vanadium.
4 Nutrients which enhance recovery, including
fluid, carbohydrate and electrolytes.
This categorization system allows for pigeonholing supplements on the basis of functionality,
although some nutrients serve multiple functions. For example, carbohydrate could fit
equally well in all four categories: as a metabolic
fuel, as a limited cellular component (during the
latter stages of prolonged exercise), as a nutrient
that provokes anabolic effects (via insulin) and as
an aid to recovery.
Kanter and Williams (1995) suggested that the
purpose of most nutritional ergogenic aids is to
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enhance energy production during exercise by
either (i) providing an additional energy source
(as in the case of carbohydrate and fat) or (ii) by
benefiting the metabolic processes that produce
energy (a catch-all category for protein, amino
acids, vitamins, minerals and sundry other substances touted to improve performance). This
two-tiered approach to categorizing sports nutrition supplements served the authors well in their
review of antioxidants, carnitine and choline
(Kanter & Williams 1995), but falls short of providing a niche for supplements with a proposed
effect on processes other than energy metabolism (e.g. amino acids, chromium, choline, goryzanol).
In the not too distant future, it is likely that
government agencies will attempt to establish
regulatory control over the nutritional supplement industry, including what might be broadly
classified as sports foods. In fact, such regulations have either been proposed or enacted in the
United States, Australia, Japan and within the
European Community. The likely result of each
attempt will be the creation of a less than perfect
way to define and categorize a group of foods,
beverages and supplements that by their very
diversity defy a simple manner of categorization.
None the less, faced with the challenge of
addressing the role of sports nutrition supplements, the following section provides an admittedly arbitrary attempt at organizing the wide
array of sports nutrition supplements into categories that allow for some degree of generalization regarding their proven or purported effects.
Role of sports nutrition products
The reader wishing a comprehensive review of
the science underlying sports nutrition products
is referred to the other chapters in this book and
to the many review articles and books previously
written on this topic.
Fluid replacement beverages
(i.e. sports drinks)
Sports drinks are the most comprehensively
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practical issues
researched of all sports nutrition products. Formulated to rapidly replace fluid lost as sweat
during physical activity, sports drinks commonly contain a mixture of mono-, di- and
oligosaccharides (as maltodextrins), minerals
(most often sodium, potassium and chloride),
along with assorted flavourings. The carbohydrate concentration of most commercially available sports drinks ranges from 5% to 8%
carbohydrate (i.e. 50–80 g carbohydrate per litre).
The physiological effectiveness of sports drink
ingestion has been well documented (Lamb &
Brodowicz 1986; Murray 1987; Maughan 1991;
Maughan et al. 1995) and the plethora of related
data provided part of the foundation for the position stand on exercise and fluid replacement
published by the American College of Sports
Medicine (ACSM 1996). Chapters 15–19 of
this text provide an excellent review of issues
regarding fluid and electrolyte homeostasis and
Chapter 8 addresses the topic of carbohydrate
feeding during exercise.
Carbohydrate-rich beverages
The value of ingesting a diet high in carbohydrate content has been well established, as
detailed in Chapters 5–8. Any food or beverage
high in carbohydrate content could conceivably
be termed a carbohydrate-loading supplement,
although this designation is usually applied to
commercial products, most often beverages.
Whether purchased in liquid form or reconstituted from a powder mix, these beverages
should contain a carbohydrate concentration in
excess of regular soft drinks (10–14% carbohydrate) and common fruit juices (12–16% carbohydrate). It is accepted at face validity that the
ingestion of adequate amounts of such products
will help athletes meet their goals for dietary
carbohydrate intake, the result of which will be
effective restoration of glycogen stores in liver
and muscle.
Complete-nutrition/energy beverages
These beverages, usually in the form of milk-
shake type drinks, contain varying combinations
of carbohydrate, protein, fat, vitamins and minerals. Some of these products contain an array of
other nutrients and metabolites. It is accepted at
face validity that the ingestion of these supplements will provide the energy and nutrients
included in them, the inference being that intake
of the nutrients will help athletes meet their daily
nutritional needs. Additional claims of product
benefits to structure or function (e.g. ‘adds lean
body mass’, ‘boosts fat metabolism by 43%’)
would require direct substantiation by acceptable scientific research.
Energy bars
This category of supplements includes solid
foods in bar form. Most bars provide 140–250
kcal (588–1050 kJ) of energy and contain varying
proportions of carbohydrate, protein, fat and
micronutrients. Most of these products are associated with statements of nutritional content (e.g.
‘contains ginseng’), although a few make structure or function claims (e.g. ‘burn more body
fat’). In the latter case, the manufacturers must
be held accountable for providing acceptable
scientific support.
Carbohydrate gels
These products are often small packets of
carbohydrate syrup (20–30 g) positioned for use
during prolonged exercise as an alternative
means of carbohydrate intake. The claims made
for these products are most often statements of
nutritional content. Most products advise the
user to ingest the gel with ample amounts of
fluid to help assure rapid gastric emptying.
Vitamin supplements
Vitamins are sold as single nutrients (e.g. vitamin
C), in combination with other vitamins (e.g. B
complex vitamins), or as vitamin–mineral tablets
that contain assorted nutrients. Some manufacturers employ a use-specific positioning for their
products that imply particular benefits (e.g. ‘an
sports nutrition products
antistress formula’). In most cases, however, the
claims for vitamin products are limited to statements of nutrient content (e.g. ‘provides 100% of
the RDA for seven important vitamins’).
The benefits of vitamin supplementation in
cases of borderline or frank vitamin deficiency
are well accepted (Clarkson 1991). Under these
circumstances, health status and performance
are improved when the deficiency is corrected.
Whether ingestion of vitamins in amounts far
exceeding the recommended dietary allowances
confer benefits to physically active people
remains a topic of much discussion and interest
(see Chapters 20–22). Future research will
undoubtedly determine if vitamin supplementation provides specific benefits to human structure and function, or serves merely as a way for
physically active people to assure adequate
micronutrient intake. Additional information on
vitamin supplementation can be found in Chapters 20–22 of this text and in review articles by
Armstrong and Maresh (1996), Clarkson (1991),
Haymes (1991), Rosenbloom et al. (1992), Sobal
and Marquart (1994) and Williams (1984).
Mineral supplements
As with vitamins, minerals are also sold singly
(e.g. chromium) or in combination (multimineral
tablets). Chapters 23–25 provide a detailed
review of mineral requirements in physically
active people, as do review articles by Armstrong
and Maresh (1996), Clarkson (1991) and Haymes
(1991). Acute or chronic deficiencies of minerals
such as sodium, calcium and iron can occur as a
result of physical activity and inadequate dietary
intake. Advertising claims for the benefits of
minerals such as boron, chromium, molybdenum, selenium and zinc have not been borne out
by scientific research (Clarkson 1991; Haymes
1991). Armstrong and Maresh (1996) identified a
number of flaws in the experimental designs of
supplementation studies that can render the data
suspect or useless. Among these are the inability
to control for mineral status of the subjects, the
absence of placebo groups, and the choice of
inappropriate assessment criteria. Some of the
529
studies that report positive structural or functional effects of mineral supplementation suffer
from one or more of the design flaws noted by
Armstrong and Maresh (1996).
Protein and amino-acid supplements
The advertising for protein and amino-acid
supplements is often based upon the notion that
physically active people, particularly bodybuilders and power lifters, require large amounts
of dietary protein. Claims for these products tout
benefits such as, ‘promotes anticatabolic activity’, ‘pack on some solid, rock-hard mass’, and
‘increases lean muscle mass and promotes fat
loss’. There is little in the way of scientific evidence to indicate that ingesting protein supplements will fulfil these promises. As indicated in
Chapters 9 and 10, although physical activity
increases the dietary requirement for protein, the
increase is easily met by consuming a normal
diet. In brief, protein and amino-acid supplements are expensive substitutes for protein-rich
foods that are readily available in the diet
(Lemon 1995).
In recent years, attention has been paid to the
effects of ingesting individual amino acids such
as glycine and glutamine or combinations of
amino acids such as the branched-chain amino
acids (leucine, isoleucine and valine) for purposes ranging from stimulating growth hormone
release to altering serotonin production in the
brain. Although future research may generate
evidence of benefits associated with the ingestion of amino acids, the current data are not compelling. In addition, the ingestion of amino-acid
supplements is not without risk (Butterfield
1991; Beltz & Doering 1993).
Putative promoters of muscle growth
A number of other substances have been advertised as being able to promote the growth
of muscle tissue. Dibencozide, g-oryzanol,
yohimbe, phosphatidylserine and vanadyl sulphate are among the ingredients that can be
found in current products promoted as having
530
practical issues
growth-enhancing properties. Additional substances are reviewed in Chapter 26. Again, there
is an absence of scientific research confirming
such effects (Rosenbloom et al. 1992; Grunewald
& Bailey 1993; Coleman & Nelson-Steen 1996).
Putative enhancers of energy metabolism
In theory, performance should be enhanced if
a product ingredient increased the ability of
muscle to resynthesize adenosine triphosphate.
The most obvious candidates for such a role
would be metabolic intermediates such as
lactate, pyruvate, citrate and other tricarboxylic
acid intermediates, enzyme-system components
such as lipoic acid, alternative fuel sources such
as medium-chain triglycerides, mediators in fuel
oxidation such as carnitine, and components of
the high-energy phosphate pool such as inosine
and creatine. Of these, creatine ingestion appears
to have the most promise as an ergogenic aid
(Greenhaff 1995). As indicated in Chapter 27, creatine ingestion is associated with an increase
in muscle creatine content, a response that may
be associated with increased performance in
very high intensity, short-duration activities.
However, as promising as creatine appears to be
as an ergogenic aid, and notwithstanding the
numerous products containing creatine as an
ingredient, it may still be premature to draw a
definitive conclusion regarding its efficacy.
While some laboratories have reported improved sprint performance associated with creatine feeding (e.g. Casey et al. 1996), others have
failed to find an effect (e.g. Barnett et al. 1996).
Although the disparate results may merely be an
artefact of differences in experimental design,
feeding protocols, subject selection, and choice of
performance critieria, more research is needed to
confirm if this is indeed the case.
Conclusion
Efficacious sports nutrition products will
continue to play an important role in helping
athletes achieve and maintain a nutritional
status that positively influences body structure
and function. The benefits of remaining well
hydrated during exercise, the advantages of
ingesting a diet high in carbohydrate content,
the importance of sodium in stimulating rapid
and complete rehydration, and the indispensible
nature of consuming adequate energy are examples of well-documented nutritional applications
around which many sports nutrition products
are based. There are, however, many products
that are associated with claims that lack scientific substantiation. Sports health professionals
involved in public-education programmes have
an obligation to help provide consumers with
up-to-date and accurate information regarding
the veracity of product claims.
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