Supplement Basics

A supplement can be a nutrient or product intended to benefit your health or athletic performance. The International Olympic Committee (IOC) 2018 consensus on dietary supplements defined them as:

“A food, food component, nutrient, or non-food compound that is purposefully ingested in addition to the habitually consumed diet with the aim of achieving a specific health and/or performance benefit.” ¹

It’s important to answer the following questions if you’re considering taking a supplement:

• Is it necessary for me to take this supplement?
• Is it safe for me to take?
• Is there evidence that it works for its intended purpose?
• Is it allowed under sports anti-doping rules?

A food-first approach is always recommended, but supplements may be beneficial additions to optimize health and performance.

A sports dietitian can assess your dietary intake and help you determine, along with your doctor, if a supplement may be needed to help achieve your goals. Importantly, supplements are not regulated, so choosing supplements that have undergone third-party testing can minimize the risk of contamination.

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What is a supplement?

A supplement is defined by the International Olympic Committee (IOC) as:

“A food, food component, nutrient, or non-food compound that is purposefully ingested in addition to the habitually consumed diet with the aim of achieving a specific health and/or performance benefit.”¹

Examples of Group A Supplements from the ABCD Classification (AIS)³

Group A supplements have strong scientific evidence and permission for use in sport.

Supplements are often used to support health, address nutrient deficiencies, or improve athletic performance and recovery.

Supplements cannot replace proper fueling, hydration, and recovery, but they can further enhance your health and performance potential when used appropriately.

Research and Data

Several audits have assessed the representation of female athletes in supplement research and found that studies on the use of medical and performance supplements among competitive female athletes are limited.^4,5

While 71% of participants in iron, calcium, and vitamin D research are women, only 13% of these studies included highly competitive female athletes.⁴

In performance supplement literature, only 23% of participants are women, and 15% of female participants are highly competitive female athletes.⁵

Are you considering starting a supplement?

If so, it’s important to ask yourself the following questions:

Do I need a supplement?

For sports foods and medical supplements, it is important to assess your nutritional status to determine whether you are already getting the nutrients you need from your diet. In many cases, an adequate, varied diet meets foundational nutrient needs while also providing other beneficial ingredients like fiber. Whole foods also have a lower risk of containing banned substances than supplements.⁶A sports dietitian can assess your dietary intake and help you determine, along with your doctor, if a supplement is needed.

A performance supplement can be used to meet nutrient needs that cannot be adequately met by food alone. When considering a performance supplement, consider your goals to determine which supplement might be most appropriate.

Situations in which a supplement may be helpful:

• Convenient, portable fueling
• Nutrient deficiencies
• Food allergies
• Dietary limitations
• Digestive intolerance
• Increased nutrient demand
• Recovery support
• Performance enhancement

Is taking a supplement safe & legal?

Supplements are not regulated like over-the-counter drugs and medications, and regulations vary around the world. In the United States, supplements are not regulated by the Food and Drug Administration (FDA).² This means that their manufacturing is not checked for quality or safety, and there is a risk of contamination and mislabeling.^7,8

In addition to safety concerns, the lack of regulation also means that supplements could inadvertently contain banned substances that can impact your ability to compete. A 2025 study examining 200 commercial products found that 35% contained substances banned by the World Anti-Doping Agency (WADA).⁹ A review suggests that 10-30% of supplements contain prohibited substances.¹⁰

The WADA List of Prohibited Substances and Methods provides a list of substances that are banned in sport. Athletes should be up to speed to understand which are banned and in what situations; the list is reviewed annually and updated every January.

To ensure supplements do not have banned substances, look for products that have been tested for quality and purity by third-party verification.

NSF Certified for Sport

Informed Sport

Banned Substance Control Group

Cologne List

HASTA