ISSN exercise & sports nutrition review update: research & recommendations


Sports Nutrition / Articles 498 Views

Evaluating the scientific merit of articles and advertisements about exercise and nutrition products is a key skill that all sports nutrition professionals must possess. To assist members and other advocates of the International Society of Sports Nutrition (ISSN) in keeping up to date about the latest findings in sports nutrition, the ISSN Exercise & Sports Nutrition Review: Research & Recommendations has been updated. The initial version of this paper was the first publication used to help launch the Journal of the International Society of Sports Nutrition (JISSN, originally called the Sports Nutrition Review Journal). This paper provides a definition of ergogenic aids and dietary supplements and discusses how dietary supplements are legally regulated. Other sections highlight how to evaluate the scientific merit of nutritional supplements and provide general nutritional strategies to optimize performance and enhance recovery. Finally, a brief overview of the efficacy surrounding many supplements commonly touted to promote skeletal muscle hypertrophy and improve physical performance is provided. Based upon the available scientific literature testing the efficacy and safety of the nutritional supplements discussed herein, all nutritional supplements discussed in this paper have been placed into three categories based upon the quality and quantity of scientific support available:

  1. A)

    Strong Evidence to Support Efficacy and Apparently Safe

  2. B)

    Limited or Mixed Evidence to Support Efficacy

  3. C)

    Little to No Evidence to Support Efficacy and/or Safety

Since the last published version of this document in 2010 [1], the general approach to categorization has not changed, but several new supplements have been introduced to the market and are subsequently reviewed in this article. In this respect, many supplements have had additional studies published that has led to some supplements being placed into a different category or removed from the review altogether. We understand and expect that some individuals may not agree with our interpretations of the literature or what category we have assigned a particular supplement, but it is important to appreciate that some classifications may change over time as more research becomes available.

Definition of an ergogenic aid

An ergogenic aid is any training technique, mechanical device, nutritional ingredient or practice, pharmacological method, or psychological technique that can improve exercise performance capacity or enhance training adaptations [24]. Ergogenic aids may help prepare an individual to exercise, improve exercise efficiency, enhance recovery from exercise, or assist in injury prevention during intense training. Although this definition seems rather straightforward, there is considerable debate regarding the ergogenic value of various nutritional supplements. A consensus exists to suggest that a nutritional supplement is ergogenic if peer-reviewed studies demonstrate the supplement significantly enhances exercise performance following weeks to months of ingestion (e.g., promotes increases in maximal strength, running speed, and/or work during a given exercise task). On the other hand, a supplement may also have ergogenic value if it acutely enhances the ability of an athlete to perform an exercise task or enhances recovery from a single exercise bout. The ISSN has adopted a broader view regarding the ergogenic value of supplements. While the muscle building and performance enhancing effects of a supplement on a single bout of exercise may lead to eventual ergogenic effects or optimized training adaptations, our view is that such evidence does not warrant “Excellent Evidence to Support Efficacy” if there is a lack of long-term efficacy data. Herein, we have adopted the view that a supplement is clearly ergogenic if most of human studies support the ingredient as being effective in promoting further increases in muscle hypertrophy or performance with exercise training. Conversely, supplements that fall short of this standard and are only supported by preclinical data (e.g., cell culture or rodent studies) are grouped into other categories.

Definition and regulation of dietary supplements

The Dietary Supplement Health and Education Act (DSHEA) and the safety of dietary supplements

Congress passed the Dietary Supplement Health and Education Act of 1994 (DSHEA), placing dietary supplements in a special category of “foods”. In October 1994, President Clinton signed DSHEA into law. This statute was enacted amid claims that the Food and Drug Administration (FDA) was distorting the then-existing provisions of the Food, Drug, and Cosmetic Act (FDCA) to improperly deprive the public of safe and popular dietary supplement products.

The law defines a “dietary supplement” as a product that is intended to supplement the diet and contains a “dietary ingredient”. By definition, “dietary ingredients” in these products may include vitamins, minerals, herbs or other botanicals, amino acids, and substances such as enzymes, organ tissues, and glandular extracts. Further, dietary ingredients may also include extracts, metabolites, or concentrates of those substances. Dietary supplements may be found in many forms such as tablets, capsules, softgels, gelcaps, liquids, or powders, but may only be intended for oral ingestion. Dietary supplements cannot be marketed or promoted for sublingual, intranasal, transdermal, injected, or in any other route of administration except oral ingestion. A supplement can be in other forms, such as a bar, as long as the information on its label does not represent the product as a conventional food or a sole item of a meal or diet.

Indeed, DSHEA clearly defines “dietary supplements” and “dietary ingredients,” it sets certain criteria for “new dietary ingredients,” and the law prevents the FDA from overreaching. Additionally, and contrary to widespread opinion, DSHEA did not leave the industry unregulated. The dietary supplement industry is in fact regulated by the FDA as a result of DSHEA. The law ensures the authority of the FDA to provide legitimate protections for the public health. The Federal Trade Commission (FTC) also continues to have jurisdiction over the marketing claims that dietary supplement manufacturers or companies make about their products. The FDA and FTC operate in a cooperative fashion to regulate the dietary supplement industry. In this respect, the extent to which information is shared and jurisdiction between these two entities overlaps with regard to marketing and advertising dietary supplements continues to increase.

In the United States, dietary supplements are classified as food products, not drugs, and there is generally no mandate to register products with the FDA or obtain FDA approval before producing or selling supplements to consumers. However, if a dietary supplement manufacturer is making a claim about their product, the company must submit the claims to FDA within 30 days of marketing the product. Compare this, for example, with Canada where under the Natural Health Product (NHP) Regulations enacted in 2004 supplements must be reviewed, approved, and registered with Health Canada. The rationale for the U.S. model is based on a presumed long history of safe use; hence there is no need to require additional safety data.

DSHEA also requires supplement marketers to include on any label displaying structure/function claims (i.e., claims that the product affects the structure or function of the body) the mandatory FDA disclaimer “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” Opponents of dietary supplements often cite this statement as evidence that the FDA does not review or approve dietary supplements. However, most dietary ingredients have been “grandfathered in” as DSHEA-compliant ingredients due to a long history of safe use, and those products containing new ingredients must be submitted by a notification to the FDA for a safety review prior to being brought to market. Although many dietary ingredients have been introduced into dietary supplements since October 1994 and have not been submitted to the FDA for a safety review, nutritional supplementation writ large is generally safe. In this regard, while there are over 50,000 dietary supplements registered with the Office of Dietary Supplement’s “Dietary Supplement Label Database”, a 2013 Annual Report (released in 2015) of the American Association of Poison Control Centers revealed zero fatalities occurred due to dietary supplements compared to 1692 deaths due to drugs [5]. Perhaps more alarming is a 2015 report by the Centers for Disease Control suggesting 2,287,273 emergency room visits were due to prescription drug-related events which dwarfs the 3266 emergency room visits due to dietary supplements (adjusted from 23,000 visits after excluding cases of older adults choking on pills, allergic reactions, unsupervised children consuming too many vitamins, and persons consuming ingredients not defined by DSHEA as a dietary supplement) [5]. Furthermore, a recent Healthcare Cost and Utilization Project Statistical Brief by Lucado et al. [6] reported approximately one in six Americans suffered from food borne illnesses in 2010, and food borne illnesses were associated with over 3.7 million treat-and-release emergency department visits, 1.3 million inpatient hospital stays, and 3000 deaths. Notwithstanding, there have been case reports of liver and kidney toxicity potentially caused by supplements containing herbal extracts [7] as well as overdoses associated with pure caffeine anhydrous ingestion [8]. Collectively, the aforementioned statistics and case reports demonstrate that while generally safe, as with food or prescription drug consumption, dietary supplement consumption can lead to adverse events in spite of DSHEA and current FDA regulations described below.

New dietary ingredients

Recognizing that new and untested dietary supplement products may pose unknown health issues, DSHEA distinguishes between products containing dietary ingredients that were already on the market and products containing new dietary ingredients that were not marketed prior to the enactment of the law. A “new dietary ingredient” (NDI) is defined as a dietary ingredient that was not marketed in the United States before October 15, 1994. DSHEA grants the FDA greater control over supplements containing NDIs. A product containing an NDI is deemed adulterated and subject to FDA enforcement sanctions unless it meets one of two exemption criteria: either (1) the supplement in question contains “only dietary ingredients which have been present in the food supply as an article used for food in a form in which the food has not been chemically altered”; or (2) there is a “history of use or other evidence of safety” provided by the manufacturer or distributor to the FDA at least 75 days before introducing the product into interstate commerce. The first criterion is silent as to how and by whom presence in the food supply as food articles without chemical alteration is to be established. The second criterion—applicable only to new dietary ingredients that have not been present in the food supply—requires manufacturers and distributors of the product to take certain actions. Those actions include submitting, at least 75 days before the product is introduced into interstate commerce, information that is the basis on which a product containing the new dietary ingredient is “reasonably expected to be safe.” That information would include: (1) the name of the new dietary ingredient and, if it is an herb or botanical, the Latin binomial name; (2) a description of the dietary supplement that contains the new dietary ingredient, including (a) the level of the new dietary ingredient in the product, (b) conditions of use of the product stated in the labeling, or if no conditions of use are stated, the ordinary conditions of use, and (c) a history of use or other evidence of safety establishing that the dietary ingredient, when used under the conditions recommended or suggested in the labeling of the dietary supplement, is reasonably expected to be safe.

In July 2011, the FDA released a Draft Guidance for Industry, entitled “Dietary Supplements: New Dietary Ingredient Notifications and Related Issues.” While a guidance does not carry the authority or the enforceability of a law or regulation, the FDA’s NDI draft guidance represented the agency’s current thinking on the topic. The guidance prompted great controversy, and FDA agreed to issue a revised draft guidance to address some of the issues raised by industry. In August 2016, FDA released a revised Draft Guidance that replaced the 2011 Draft Guidance. The purpose of the 2016 Draft Guidance was to help manufacturers and distributors decide whether to submit a premarket safety notification to FDA, help prepare NDI notifications in a manner that allows FDA to review and respond more efficiently and quickly, and to improve the quality of NDI notifications. The 2016 Draft Guidance has been criticized by industry and trade associations for its lack of clarity and other problems. Some of these issues include the lack of clarity regarding Pre-DSHEA, (Grandfathered), ingredients and FDA requiring an NDI notification even if another manufacturer has submitted a notification.

The lack of clarity surrounding the “new” Draft Guidance has led to many NDI notifications being rejected by FDA for lack of safety data and other issues. Other companies have opted to utilize the “Self-Affirmed Generally Recognized as Safe (GRAS)” route in order to “bypass” the NDI notification process. Self-Affirmed GRAS is when a company has a team of scientific experts evaluate the safety of their ingredient. There is no requirement that the safety dossier be submitted to FDA but is used by the company as an internal document that may be relied upon if the ingredient is challenged by the FDA. FDA has expressed its concern with this practice and does not encourage dietary supplement manufacturers to use Self-Affirmed GRAS to avoid submitting NDI notifications. In any event, the likelihood of another revised Draft Guidance from FDA becoming available in the future is high, and possibly more enforcement actions taken against companies that market an NDI without submitting a notification.

Adverse event reporting

In response to growing criticism of the dietary supplement industry, the 109th Congress passed the first mandatory Adverse Event Reporting (AER) legislation for the dietary supplement industry. In December 2006, President Bush signed into law the Dietary Supplement and Nonprescription Drug Consumer Protection Act, which took effect on December 22, 2007. After much debate in Congress and input from the FDA, the American Medical Association (AMA), many of the major supplement trade associations, and a host of others all agreed that the legislation was necessary and the final version was approved by all. In short, the Act requires that all “serious adverse events” regarding dietary supplements be reported to the Secretary of Health and Human Services. The law strengthens the regulatory structure for dietary supplements and builds greater consumer confidence, as consumers have a right to expect that if they report a serious adverse event to a dietary supplement marketer the FDA will be advised about it.

An adverse event is any health-related event associated with the use of a dietary supplement that is adverse. A serious adverse event is an adverse event that (A) results in (i) death, (ii) a life-threatening experience, (iii) inpatient hospitalization, (iv) a persistent or significant disability or incapacity, or (v) a congenital anomaly or birth defect; or (B) requires, based on reasonable medical judgment, a medical or surgical intervention to prevent an outcome described under subparagraph (A). Once it is determined that a serious adverse event has occurred, the manufacturer, packer, or distributor (responsible person) of a dietary supplement whose name appears on the label of the supplement shall submit to the Secretary of Health and Human Services any report received of the serious adverse event accompanied by a copy of the label on or within the retail packaging of the dietary supplement. The responsible person has 15 business days to submit the report to FDA after being notified of the serious adverse event. Following the initial report, the responsible person must submit follow-up reports of new medical information that they receive for one-year.

Adulterated supplements

The FDA has various options to protect consumers from unsafe supplements. The Secretary of the Department of Health and Human Services (which falls under FDA oversight) has the power to declare a dangerous supplement to be an “imminent hazard” to public health or safety and immediately suspend sales of the product. The FDA also has the authority to protect consumers from dietary supplements that do not present an imminent hazard to the public but do present certain risks of illness or injury to consumers. The law prohibits introducing adulterated products into interstate commerce. A supplement shall be deemed adulterated if it presents “a significant or unreasonable risk of illness or injury”. The standard does not require proof that consumers have actually been harmed or even that a product will harm anyone. It was under this provision that the FDA concluded that dietary supplements containing ephedra, androstenedione, and DMAA presented an unreasonable risk. Most recently, FDA imposed an importation ban on the botanical Mitragyna speciose, better known as Kratom. In 2016, FDA issued Import Alert #54–15, which allows for detention without physical examination of dietary supplements and bulk dietary ingredients that are, or contain, Kratom. Criminal penalties are present for a conviction of introducing adulterated supplement products into interstate commerce. While the harms associated with dietary supplements may pale in comparison to those linked to prescription drugs, recent pronouncements from the U.S. Department of Justice confirm that the supplement industry is being watched vigilantly to protect the health and safety of the American public.

Good manufacturing practices

When DSHEA was passed in 1994, it contained a provision requiring that the FDA establish and enforce current Good Manufacturing Practices (cGMPs) for dietary supplements. However, it was not until 2007 that the cGMPs were finally approved, and not until 2010 that the cGMPs applied across the industry, to large and small companies alike. The adherence to cGMPs has helped protect against contamination issues and should serve to improve consumer confidence in dietary supplements. The market improved as companies became compliant with cGMPs, as these regulations imposed more stringent requirements such as Vendor Certification, Document Control Procedures, and Identity Testing. These compliance criteria addressed the problems that had damaged the reputation of the industry with a focus on quality control, record keeping, and documentation.

However, it does appear that some within the industry continue to struggle with compliance. In Fiscal Year 2017, it was reported that approximately 23.48% of the FDA’s 656 total cGMP inspections resulted in citations for failing to establish specifications for the identity, purity, strength, and composition of dietary supplements. Further, 18.47% of those inspected were cited for failing to establish and/or follow written procedures for quality control operations. Undoubtedly, relying on certificates of analysis from the raw materials supplier without further testing, or failing to conduct identity testing of a finished product, can result in the creation of a product that contains something it should not contain such as synthetic chemicals or even pharmaceutical drugs. All members of the industry need to ensure compliance with cGMPs.

Marketing claims

According to the 1990 Nutrition Labeling and Education Act (NLEA), the FDA can review and approve health claims (claims describing the relationship between a food substance and a reduced risk of a disease or health-related condition) for dietary ingredients and foods. However, since the law was passed it has only approved a few claims. The delay in reviewing health claims of dietary supplement ingredients resulted in a lawsuit, Pearson v. Shalala, filed in 1995. After years of litigation, in 1999 the U.S. Court of Appeals for the District of Columbia Circuit ruled that qualified health claims may be made about dietary supplements with approval by FDA, as long as the statements are truthful and based on adequate science. Supplement or food companies wishing to make health claims or qualified health claims about supplements can submit research evidence to the FDA for review.

The FTC also regulates the supplement industry. Unsubstantiated claims invite enforcement by the FTC (along with the FDA, state district attorney offices, groups like the Better Business Bureau, and plaintiff’s lawyers who file class action lawsuits). The FTC has typically applied a substantiation standard of “competent and reliable scientific evidence” to claims about the benefits and safety of dietary supplements. FTC case law defines “competent and reliable scientific evidence” as “tests, analyses, research, studies, or other evidence based on the expertise of professionals in the relevant area, that has been conducted and evaluated in an objective manner by persons qualified to do so, using procedures generally accepted in the profession to yield accurate and reliable results.” The FTC has claimed that this involves providing at least two clinical trials showing efficacy of the actual product, within a population of subjects relevant to the target market, supporting the structure/function claims that are made. While the exact requirements are still evolving, the FTC has acted against several supplement companies for misleading advertisements and/or structure/function claims.

A safer industry ahead

As demonstrated, while some argue that the dietary supplement industry is “unregulated” and/or may have suggestions for additional regulation, manufacturers and distributors of dietary supplements must adhere to several federal regulations before a product can go to market. Further, before marketing products, they must have evidence that their supplements are generally safe to meet all the requirements of DSHEA and FDA regulations. For this reason, over the last 20 years, many established supplement companies have employed research and development directors who help educate the public about nutrition and exercise, provide input on product development, conduct preliminary research on products, and/or assist in coordinating research trials conducted by independent research teams (e.g., university-based researchers or clinical research sites). These companies also consult with marketing and legal teams with the responsibility to ensure structure/function claims do not misrepresent results of research findings. This has increased job opportunities for sports nutrition specialists as well as enhanced external funding opportunities for research groups interested in exercise and nutrition research.

While some companies have falsely attributed research on different dietary ingredients or dietary supplements to their own products, suppressed negative research findings, and/or exaggerated results from research studies, the trend in the sports nutrition industry has been to develop scientifically sound supplements. This trend toward greater research support is the result of: (1) attempts to honestly and accurately inform the public about results; (2) efforts to obtain data to support safety and efficacy on products for the FDA and the FTC; and/or, (3) endeavors to provide scientific evidence to support advertising claims and increase sales. While the push for more research is due in part to greater scrutiny from the FDA and FTC, it is also in response to an increasingly competitive marketplace where established safety and efficacy attracts more consumer loyalty and helps ensure a longer lifespan for the product in commerce. Companies that adhere to these ethical standards tend to prosper while those that do not will typically struggle to comply with FDA and FTC guidelines resulting in a loss of consumer confidence and an early demise for the product.

Product development and quality assurance

A common question posed by athletes, parents, and professionals surrounding dietary supplements relates to how they are manufactured and perceived supplement quality. In several cases, established companies who develop dietary supplements have research teams who scour the medical and scientific literature looking for potentially effective nutrients. These research teams often attend scientific meetings and review the latest patents, research abstracts presented at scientific meetings, and research publications. Leading companies invest in basic research on nutrients before developing their supplement formulations and often consult with leading researchers to discuss ideas about dietary supplements and their potential for commercialization. Other companies wait until research has been presented in patents, research abstracts, or publications before developing nutritional formulations featuring the nutrient. Upon identification of new nutrients or potential formulations, the next step is to contact raw ingredient suppliers to see if the nutrient is available, if it is affordable, how much of it can be sourced and what is the available purity. Sometimes, companies develop and pursue patents involving new processing and purification processes because the nutrient has not yet been extracted in a pure form or is not available in large quantities. Reputable raw material manufacturers conduct extensive tests to examine purity of their raw ingredients. When working on a new ingredient, companies often conduct series of toxicity studies on the new nutrient once a purified source has been identified. The company would then compile a safety dossier and communicate it to the FDA as a New Dietary Ingredient submission, with the hopes of it being allowed for lawful sale.

When a powdered formulation is designed, the list of ingredients and raw materials are typically sent to a flavoring house and packaging company to identify the best way to flavor and package the supplement. In the nutrition industry, several main flavoring houses and packaging companies exist who make many dietary supplements for supplement companies. Most reputable dietary supplement manufacturers submit their production facilities to inspection from the FDA and adhere to GMP, which represent industry standards for good manufacturing of dietary supplements. Some companies also submit their products for independent testing by third-party companies to certify that their products meet label claims and that the product is free of various banned ingredients. For example, the certification service offered by NSF International includes product testing, GMP inspections, ongoing monitoring and use of the NSF Mark indicating products comply with inspection standards, and screening for contaminants. More recently, companies have subjected their products for testing by third party companies to inspect for banned or unwanted substances. These types of tests help ensure that the dietary supplement made available to athletes do not contained substances banned by the International Olympic Committee or other athletic governing bodies (e.g., NFL, NCAA, MLB, NHL, etc.). While third-party testing does not guarantee that a supplement is void of banned substances, the likelihood is reduced (e.g., Banned Substances Control Group, Informed Choice, NSF, etc.). Moreover, consumers can request copies of results of these tests and each product that has gone through testing and earned certification can be researched online to help athletes, coaches and support staff understand which products should be considered. In many situations, companies who are not willing to provide copies of test results or certificates of analysis should be viewed with caution, particularly for individuals whose eligibility to participate might be compromised if a tainted product is consumed.

Evaluation of nutrition ergogenic aids

The ISSN recommends that potential consumers undertake a systematic process of evaluating the validity and scientific merit of claims made when assessing the ergogenic value of a dietary supplement [1, 4]. This can be accomplished by examining the theoretical rationale behind the supplement and determining whether there is any well-controlled data showing the supplement is effective. Supplements based on sound scientific rationale with direct, supportive research showing effectiveness may be worth trying or recommending. However, those based on unsound scientific results or offer little to no data supporting the ergogenic value of the actual supplement/technique may not be worthwhile. Sports nutrition specialists should be a resource to help their clients interpret the scientific and medical research that may impact their welfare and help them train more effectively. The following are recommended questions to ask when evaluating the potential ergogenic value of a supplement.

Does the theory make sense?

Most supplements that have been marketed to improve health or exercise performance are based on theoretical applications derived from basic science or clinical research studies. Based on these preliminary studies, a dietary approach or supplement is often marketed to people proclaiming the benefits observed in these basic research studies. Although the theory may appear relevant, critical analysis of this process often reveals flaws in the scientific logic or that the claims made do not quite match up with the cited literature. By evaluating the literature one can discern whether or not a dietary approach or supplement has been based on sound scientific evidence. To do so, one is recommended to first read reviews about the training method, nutrient, or supplement from researchers who have been intimately involved in the available research and consult reliable references about nutritional and herbal supplements [1, 9]. To aid in this endeavour, the ISSN has published position statement on topics related to creatine [10], protein [11], beta-alanine [12], nutrient timing [13], caffeine [14], HMB [15], meal frequency [16], energy drinks [17], and diets and body composition [18]. Each of these documents would be excellent resources for any of these topics. In addition, other review articles and consensus statements have been published by other researchers and research groups that evaluate dietary supplements, offer recommendations on interpreting the literature, and discuss the available findings for several ingredients that are discussed in this document [1921]. We also advise consumers to conduct a search on the nutrient, key ingredients or the supplement itself on the National Library of Medicine’s Pub Med Online ( A quick look at these references will often help determine if the theoretical impetus for supplementing with an ingredient is plausible or not. Proponents of ergogenic aids often overstate claims made about training devices and dietary supplements while opponents of ergogenic aids and dietary supplements are often either unaware or are ignorant of research supporting their use. Sports nutrition specialists have the responsibility to know the literature and search available databases to evaluate the level of merit surrounding a proposed ergogenic aid.

Is the supplement legal and safe?

An initial question that should be asked is whether the supplement is legal and/or safe. Some athletic associations have banned the use of various nutritional supplements (e.g., prohormones, ephedra that contains ephedrine, “muscle building” supplements, etc.) and many professional sports organization have now written language into their collective bargaining agreements that products made available by the team must be NSF certified as safe for sport. Obviously, if the supplement is banned, the sports nutrition specialist should discourage its use. In addition, many supplements lack appropriate long-term safety data. People who consider taking nutritional supplements should be well aware of the potential side effects so they can make an informed decision whether to use a supplement. Additionally, they should consult with a knowledgeable physician to see if any underlying medical problems exist that may contraindicate its use. When evaluating the safety of a supplement, it is suggested to determine if any side effects have been reported in the scientific or medical literature. In particular, we suggest determining how long a particular supplement has been studied, the dosages evaluated, and whether any side effects were observed. We also recommend consulting the Physician’s Desk Reference (PDR) for nutritional supplements and herbal supplements to see if any side effects have been reported and/or if there are any known drug interactions. If no side effects have been reported in the scientific/medical literature, we generally will view the supplement as safe for the length of time and dosages evaluated. Unfortunately, many available supplements have not had basic safety studies completed that replicate the length of time and dosages being used.

Is there any scientific evidence supporting the ergogenic value?

The next question to ask is whether any well-controlled data are available showing effectiveness of the proposed ergogenic aid in athletic populations or people regularly involved in exercise training. The first place to look is the list of references cited in marketing material supporting their claims. Are the abstracts or articles cited just general references or specific studies that have evaluated the efficacy of the nutrients included in the formulation or of the actual supplement? From there, one can critically evaluate the cited abstracts and articles by asking a series of questions:

  • Are the studies basic research done in animals/clinical populations or have the studies been conducted on athletes/trained subjects? For perspective, studies reporting improved performance in rats or an individual diagnosed with type 2 diabetes may be insightful, but research conducted on non-diabetic athletes is much more practical and relevant.

  • Were the studies well controlled? For ergogenic aid research, the gold standard study design is a randomized, double-blind, placebo controlled clinical trial. This means that neither the researcher nor the subject is aware which group received the supplement or the placebo during the study and that the subjects were randomly assigned into the placebo or supplement group. An additional element of rigor is called a cross-over design, where each subject, at different times (separated by an interval known as a “washout period”), is exposed to each of the treatments. While utilization of a cross-over design is not always feasible, it reduces the element of variability within a participant and subsequently, increases the strength of study’s findings. At times, supplement claims have been based on poorly designed studies (i.e., small groups of subjects, no control group, use of unreliable tests, etc.) or testimonials which make interpretation more difficult. Well-controlled clinical trials provide stronger evidence as to the potential ergogenic value and importantly how the findings can best be used.

  • Do the studies report statistically significant results or are claims being made on non-significant means or trends? Appropriate statistical analysis of research results allows for an unbiased interpretation of data. Although studies reporting statistical trends may be of interest and lead researchers to conduct additional research, studies reporting statistically significant results are obviously more convincing. With this said, it is important for people to understand that oftentimes the potential effect a dietary supplement or diet regimen may have above and beyond the effect seen from the exercise bout or an accepted dietary approach is quite small. In addition, many studies examining a biochemical or molecular biology mechanism can require invasive sampling techniques or the study population being recruited is unique (very highly trained) resulting in a small number of study participants. When viewed together, the combination of these two considerations can result in statistical outcomes that do not reach statistical significance even though large mean changes were observed. In these situations, the reporting of confidence intervals on the mean change, individual responses from all participants to the investigated treatment and/or effect sizes are additional pieces of information that can allow for a more accurate interpretation. In all such cases, additional research is warranted to further examine the potential ergogenic aid before conclusions can be made.

  • Do the results of the cited studies match the claims made about the supplement or do they accurately portray the response of the supplement against an appropriate placebo or control group? It is not unusual for marketing claims to greatly exaggerate the results found in the actual studies and do so by focusing upon just the outcomes within the supplement (treatment) group as opposed to how the supplement group changed in comparison to how a placebo group changed. Similarly, it is not uncommon for ostensibly compelling results, that may indeed be statistically significant, to be amplified while other relevant findings of significant consumer interest are obscured or omitted (e.g. a dietary supplement showing statistically significant increases in circulating testosterone yet changes in body composition or muscular performance were not superior to a placebo). The only way to determine this is to read the entire article versus focusing an entire study’s interpretation on the provided abstract or even the article citation, and compare results observed in the studies to the available marketing claims. Reputable companies accurately and completely report results of studies so that consumers can make informed decisions about using a product.

  • Were results of the study presented at a reputable scientific meeting and/or published in a peer-reviewed scientific journal? At times, claims are based on research that has either never been published or only published in an obscure journal. The best research is typically presented at respected scientific meetings and/or published in reputable peer-reviewed journals. Three ways to determine a journal’s reputation is either: 1) identify the publisher, 2) the “impact factor” of the journal or 3) whether or not the journal is indexed and subsequently available for review on Pub Med ( Many “peer-reviewed” journals are published by companies with ties to, or are actually owned by, companies that do business with various nutritional products (even though they may be available on PubMed). Therefore, we recommend looking up the publisher’s website and see how many other journals they publish. If you see only a few other journals this is a suggestion that the journal is not a reputable journal. Additionally, one can also look up how many articles have been published by the journal in the last 6–12 months and how many of these articles are well-conducted studies. Alternatively, one can also inquire about the impact factor, a qualitative ranking determined by the number of times a journal’s articles are cited. Impact factors are determined and published by Thomson Reuters under Journal Citation Reports® (a subscription service available at most university libraries). Most journals list their impact factor on the journal home page. Historically, those articles that are read and cited the most are the most impactful scientifically.

  • Have the research findings been replicated? If so, have the results only been replicated at the same laboratory? The best way to know an ergogenic aid works is to see that results have been replicated in several studies preferably by several separate, distinct research groups. The most reliable ergogenic aids are those in which multiple studies, conducted at different labs, have reported similar results of safety and efficacy. Additionally, replication of results by different, unaffiliated labs with completely different authors also removes or reduces the potentially confounding element of publication bias (publication of studies showing only positive results) and conflicts of interest. A notable number of studies on ergogenic aids are conducted in collaboration with one or more research scientists or co-authors that have a real or perceived economic interest in the outcome of the study. This could range from being a co-inventor on a patent application that is the subject of the ergogenic aid, being paid or receiving royalties from the creation of a dietary supplement formulation, providing consulting services for the company or having stock options or shares in a company that owns or markets the ergogenic aid described in the study. An increasing number of journals require disclosures by all authors of scientific articles, and including such disclosures in published articles. This is driven by the aim of providing greater transparency and research integrity. It is important to emphasize that disclosure of a conflict of interest does not alone discredit or dilute the merits of a research study. The primary thrust behind public disclosures of potential conflicts of interest is first and foremost transparency to the reader and second to prevent a later revelation of some form of confounding interest that has the potential of discrediting the study in question, the findings of the study, the authors, and even the research center or institution where the study was conducted.

Classifying and categorizing supplements

Dietary supplements may contain carbohydrate, protein, fat, minerals, vitamins, herbs, enzymes, metabolic intermediates (i.e., select amino acids), or various plant/food extracts. Supplements can generally be classified as convenience supplements (e.g., energy bars, gels, blocks, meal replacement powders, or ready to drink supplements) designed to provide a convenient means of meeting necessary energy or macronutrient needs while also providing support towards attempts at managing caloric intake, weight gain, weight loss, and/or performance enhancement. As discussed previously, evaluating the available scientific literature is an important step in determining the efficacy of any diet, diet program or dietary supplement. In considering this, nutritional supplements can be categorized in the following manner:

  1. I.

    Strong Evidence to Support Efficacy and Apparently Safe: Supplements that have a sound theoretical rationale with the majority of available research in relevant populations using appropriate dosing regimens demonstrating both its efficacy and safety.

  2. II.

    Limited or Mixed Evidence to Support Efficacy: Supplements within this category are characterized as having a sound scientific rationale for its use, but the available research has failed to produce consistent outcomes supporting its efficacy. Routinely, these supplements require more research to be completed before researchers can begin to understand their impact. Importantly, these supplements have no available evidence to suggest they lack safety or should be viewed as harmful.

  3. III.

    Little to No Evidence to Support Efficacy and/or Safety: Supplements within this category generally lack a sound scientific rationale and the available research consistently shows it to lack efficacy. Alternatively, supplements that may be harmful to one’s health or to lack safety are also placed in this category.

Several factors are evaluated when beginning to counsel individuals who regularly complete exercise training. First, a clear understanding of the athlete’s goals and the time with which they have to meet those goals is important. In addition to monitoring load and recovery, an evaluation of the individual’s diet and training program should also be completed. To accomplish this, one should make sure the athlete is eating an energy balanced, nutrient dense diet that meets their estimated daily energy needs and that they are training intelligently. Far too many athletes or coaches focus too heavily upon supplementation or applications of supplementation and neglect these key fundamental aspects. Following this, we suggest that they generally only recommend supplements in category I (i.e., ‘Strong Evidence to Support Efficacy and Apparently Safe’). If an athlete is interested in trying supplements in category II (i.e., ‘Limited or Mixed Evidence to Support Efficacy’), the athlete should make sure they understand these supplements are more experimental and they may or may not see the type of results claimed. Obviously, the ISSN does not support athletes taking supplements in category III (i.e., ‘Little to No Evidence to Support Efficacy and/or Safety’). We believe this approach is scientifically substantiated and offers a balanced view as opposed to simply dismissing the use of all dietary supplements.

General dietary guidelines for active individuals

A well-designed diet that meets energy intake needs and incorporates proper timing of nutrients is the foundation upon which a good training program can be developed [22, 23]. Research has clearly shown that lacking sufficient calories and/or enough of the right type of macronutrients may impede an athlete’s training adaptations, while athletes who consume a balanced diet that meets energy needs can augment physiological training adaptations. Moreover, maintaining an energy deficient diet during training may lead to loss of muscle mass, strength, and bone mineral density in addition to an increased susceptibility to illness and injuries, disturbances in immune, endocrine and reproductive function, and an increased prevalence of overreaching and/or overtraining. Incorporating good dietary practices as part of a training program is one way to help optimize training adaptations and prevent overtraining. The following is an overview of energy intake recommendations and major nutrient needs for active individuals.

Energy needs

The primary component to optimize training and performance through nutrition is to ensure the athlete is consuming enough calories to offset energy expenditure [2226]. People who participate in a general fitness program (e.g., exercising 30–40 min per day, 3 times per week) can typically meet nutritional needs following a normal diet (e.g., 1800–2400 kcals/day or about 25–35 kcals/kg/day for a 50–80 kg individual) because their caloric demands from exercise are not too great (e.g., 200–400 kcals/session). However, athletes involved in moderate levels of intense training (e.g., 2–3 h per day of intense exercise performed 5–6 times per week) or high volume intense training (e.g., 3–6 h per day of intense training in 1–2 workouts for 5–6 days per week) may expend 600–1200 kcals or more per hour during exercise [24]. For this reason, their caloric needs may approach 40–70 kcals/kg/day (2000–7000 kcals/day for a 50–100 kg athlete). For elite athletes, energy expenditure during heavy training or competition will further exceed these levels [27, 28]. For example, energy expenditure for cyclists to compete in the Tour de France has been estimated as high as 12,000 kcals/day (150–200 kcals/kg/day for a 60–80 kg athlete) [29, 30]. Additionally, caloric needs for large athletes (i.e., 100–150 kg) may range between 6000 and 12,000 kcals/day depending on the volume and intensity of different training phases [31].

Although some argue that athletes can meet caloric needs simply by consuming a well-balanced diet, it is often very difficult for larger athletes and athletes engaged in high volume/intense training to be able to eat enough food, on a daily basis, to meet caloric needs [2, 29, 30, 3234]. This point was clearly highlighted in a review by Burke who demonstrated that carbohydrate needs are largely unmet by high-level athletes [22]. Additionally it is difficult to consume enough food and maintain gastrointestinal comfort to train or race at peak levels [35]. Maintaining an energy deficient diet during training often leads to a number of physical (i.e., loss of fat-free mass, illness, reduced sleep quality, incomplete recovery, hormonal fluctuations, increased resting heart rate, etc.) and psychological (i.e., apathy towards training, heightened stress) adverse outcomes [23, 27]. Nutritional analyses of athletes’ diets have revealed that many are susceptible to maintaining negative energy intakes during training. It is still a question whether there may be specific individualized occasions when negative energy balance may enhance performance in the days prior to running performance [36]. Populations susceptible to negative energy balance include runners, cyclists, swimmers, triathletes, gymnasts, skaters, dancers, wrestlers, boxers, and athletes attempting to lose weight too quickly [37]. Additionally, female athletes are at particular risk of under fueling due to both competitive and aesthetic demands of their sport and their surrounding culture. Female athletes have been reported to have a high incidence of eating disorders [38]. Low or reduced energy availability (LEA) is linked to functional hypothalamic oligomenorrhea/amenorrhea (FHA), which is frequently reported in weight sensitive sports. This makes LEA a major nutritional concern for female athletes [39]. Consequently, it is important for the sports nutrition specialist working with athletes to assess athletes individually to ensure that athletes are well fed according to the goals of their sport and their health, and consume enough calories to offset the increased energy demands of training, and maintain body weight. Although this sounds relatively simple, intense training often suppresses appetite and/or alters hunger patterns so that many athletes do not feel like eating [37, Read more