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A–Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance: Part 48
  1. A Vernec1,
  2. S J Stear2,
  3. L M Burke3,
  4. L M Castell4
  1. 1World Anti-Doping Agency, Montreal, Quebec, Canada
  2. 2Performance Influencers Limited, London, UK
  3. 3Australian Institute of Sport, Canberra, Australia
  4. 4Green Templeton College, University of Oxford, Oxford, UK
  1. Correspondence to L M Castell, Green Templeton College, University of Oxford, Oxford OX2 6HG, UK; lindy.castell{at}

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Introductory remarks

As we end this series of reviews of supplements and sports foods, it is fitting that the last words should come from the World Anti-Doping Agency. After all, the contravention of anti-doping rules due to the ingestion of prohibited substances that are ingredients or contaminants of some supplements and sports foods is a key issue which must be taken into account whenever an athlete decides whether or not to use such products.

The World Anti-Doping Agency

A Vernec

Athletes have a long history of using substances in an attempt to gain an advantage in sporting competitions. The ancient Greeks and Romans used herbs, fungi, poppy seeds and stimulants such as strychnine in order to boost performance.1 In the modern era, this practice continued mostly with the use of stimulants and narcotics. Sports federations took notice and in 1928 the International Association of Athletics Federations (IAAF) became the first federation to prohibit the use of performance-enhancing drugs (PEDs), although there would be no testing in sport for another 40 years.2

Amphetamine use was involved in the deaths of cyclists Knud Jensen and Tommy Simpson in the 1960 Olympic Games and the 1967 Tour de France respectively: this spurred the development of the International Olympic Commissions (IOC) Medical Commission, which published the first IOC Prohibited List in 1967. This became the de facto Prohibited List for Olympic Sport Federations. The ‘Festina affair’ (1998 Tour de France), where a team trainer's car was found to contain a panoply of PEDs, was the catalyst to create a new organisation to harmonise, coordinate and promote the fight against doping in sport in all its forms.3 The IOC convened the first World Conference in Doping in Sport in 1999, which resulted in the formation of the World Anti-Doping Agency (WADA).

WADA is a unique, independent body representing equally sport and the governments of the world. The World Anti-Doping Code is the core document on which anti-doping programmes are modelled. The first version of the Code came into effect in January 2004. There are presently over 600 signatories, including almost all the world's sport federations. The Code applies to Athletes, as defined by their national anti-doping organisations (NADOs) or international federations. Who is considered an athlete for anti-doping purposes may vary widely and a NADO may still test recreational athletes but not apply all elements of the Code, for example, the requirement for whereabouts or advanced therapeutic use exemptions. Athletes may be subjected to sanctions based on possession or trafficking of prohibited substances and not simply due to a positive doping test. However, it is important to be aware that criminal legislation exists in certain countries (eg, for narcotics) which may be in addition to, or completely separate from, anti-doping sanctions.

WADA also took over the role of publishing the Prohibited List (List), revised annually since 2004. The List has expanded considerably from the original IOC Prohibited List of the 1960s and contains numerous classes of substances as well as prohibited methods such as blood manipulation. A substance (or method) is considered for inclusion if it meets any two of the following criteria: (1) potential for performance enhancement; (2) detrimental to the athlete's health and (3) contrary to the spirit of sport. The deliberations on whether to include substances in the List are a highly interactive and consultative process which includes stakeholders and experts. It is impractical to list all known and possible compounds; thus, most of the prohibited classes contain an important clause stating: ‘…and other substances with similar chemical structure or similar biological effect(s).’4

Some substances have permitted routes of administration, (eg, glucocorticosteroids are allowed by inhalation or topically). A few substances are permitted but only to a certain threshold level (eg, pseudoephedrine). The List is divided into substances prohibited in competition only (eg, stimulants), and those prohibited at all times (eg, anabolic steroids and erythropoietin). It is irrelevant whether the prohibited substance is synthetic or from botanical sources or whether it is considered a pharmaceutical product or a dietary supplement.

‘Strict Liability’ means that every athlete is responsible for the substances found in their bodily specimen during a doping control sample analysis. The first line of defence for many cheating athletes has been to claim that the positive test resulted from a tainted dietary supplement. Many of these same athletes later confessed to deliberate ingestion of a prohibited substance. The athlete's responsibility to explain how a prohibited substance entered his/her body (Strict Liability) has existed for many years, being initially implemented by the IOC. It has withstood the scrutiny of the Court of Arbitration in Sport and civil courts, and is a balance between protecting all athletes by ensuring fair, clean sport and the rights of individual athletes.

For an athlete confronted with an anti-doping rule violation, section 10.5 of the Code5 allows for no sanction, or reduced sanctions, if the athlete can demonstrate no fault or no significant fault. As far as supplements are concerned, simply stating the unknowing ingestion of a tainted dietary supplement is not sufficient—an athlete would have to demonstrate clearly that every reasonable precaution was taken to avoid ingestion of a prohibited substance.

An athlete taking a spiked supplement with intent to dope may claim that he/she did not realise the product contained a prohibited substance. It is difficult to know the intent: nevertheless, the athlete will benefit from the ergogenic effect of the prohibited substance and have an unfair advantage over their competitor. There are many cautionary tales of athletes taking energy boosting supplements before or during the games and subsequently being sanctioned. Many dietary supplements that promise to enhance performance either contain a prohibited substance or are an example of false advertising.

The reality is that a significant percentage (5–20%) of supplements contain prohibited substances, either by inadvertent contamination or deliberate adulteration, during the production process. This phenomenon has been demonstrated repeatedly,6–9 and sporting federations as well as anti-doping organisations continue to impress this warning upon athletes. For example, several athletes have been recently sanctioned over the stimulant methylhexaneamine (MHA), explicitly prohibited since 2009. This was considered to be a dietary supplement from geranium oil, despite the fact that several studies, including a very recent one,10 demonstrated that its presence in supplements was not from geranium oil but due to the addition of synthetic MHA. Whether natural or synthetic, athletes need to avoid these types of products.

Many athletes continue to take supplements to try and improve recovery from training or to gain a performance edge in competition or are advised that supplements are necessary for health maintenance. Dietary supplement use by high-level athletes is estimated at 65–95%.11–13 Supplement commercialisation is a multibillion dollar industry where many claims are made with little scientific evidence; regulation for purity or side effects is still lacking in many countries. Members of the athletes’ entourage often push substances without sufficiently understanding physiology or nutrition. There are a very limited number of dietary supplements which are permitted and considered ergogenic.14 ,15 Athletes need to focus on proper training, optimal recovery practices and wholesome nutrition regimens before they even consider supplements. Some education programmes appear to be resulting in decreased supplement use among Olympic athletes.16

If an athlete truly believes he/she should take a dietary supplement, everything should be done to minimise the risk:

  1. Do not rely on advice from friends, fellow athletes or coaches but undergo a proper evaluation by a qualified physician and/or sports nutrition professional familiar with sport and anti-doping rules. It is quite likely that dietary supplements are not necessary and nutrient deficiencies may be corrected from food sources.

  2. Avoid any product making claims of performance enhancement or any exaggerated claims or uses the words: ‘stimulant, energy or muscle booster, enhancer, legal or alternate steroid, extreme, blast, weight loss’. Even if no prohibited substance is listed on the label, the product may be spiked with one.

  3. Herbal stimulants and prohormones are especially high risk. Use of the terms herbal or natural does not in any way mean that the product does not contain a prohibited substance.

  4. Some companies offer guarantees of purity or are certified by other companies that do quality control. Verify the third party testing system reputation and remember there are no absolute guarantees.

  5. Avoid any company that states their products are WADA approved. WADA or its accredited laboratories never test supplements or any products when not part of a doping control process. WADA cannot recommend any company or quality control system. In order to guarantee purity, each product batch would have to be tested for all prohibited substances.

  6. Avoid products containing multiple ingredients as there is a higher risk of contamination. Vitamins and minerals (often classified as supplements) should be from reputable pharmaceutical companies and should not be mixed with other products.

  7. Seek guidance from your anti-doping organisation about recent information on contaminated or dangerous products in your part of the world (eg, USA Anti-Doping Agency High Risk List).

Although athletes must exhibit utmost caution when using supplements due to risk of contamination, governmental authorities also have a duty to endeavour to ensure proper regulation and quality control within the supplement industry. Some initiatives are trying to improve this situation. According to Article 10, UNESCO International Convention against Doping in Sport, governments must encourage producers and distributors of dietary or nutritional supplements to establish marketing best practices, including accurate labelling, quality assurance and avoidance of false marketing. In a survey (UNESCO Conference of Parties 2011), only 43% of governments responded that they implemented extensive or substantial measures to address these issues.17

Furthermore, a more systematic approach is needed for analysing risks and benefits of dietary supplements.18 The real risks to health of ingesting potentially dangerous substances contained in poorly regulated supplements are occasionally lost in the discussion of inadvertent doping.19 ,20

Anti-doping regulations were developed over many years to promote fairness in sport and to protect the health of the athlete. Athletes are keen to improve their performance and nutrition may play an integral part in their overall plan. However, when athletes embark upon using performance-enhancing supplements, the risks often outweigh the benefits. Improved regulation of the dietary supplement industry would go a long way towards reducing the risks, but the onus remains on the athlete to make the right choices.


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  • Competing interests None.

  • Provenance and peer review Commissioned; not externally peer reviewed.

  • ▸ References to this paper are available online at

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