How do you decide whether a supplement is worth the risk?

Prevalence estimates for supplement use in athletes commonly range from about 40% to 70%, depending on the sport, the competitive level, the age and sex of the group. It also depends on methodology; how the survey was done. Most athletes and coaches ask the question: does it work? That is a reasonable question, and for a small number of supplements we can answer it well, although it is hardly ever a "yes" or "no", it is usually a answer that is more like “maybe but it depends”. On its own it is the wrong question, because a supplement that in theory works can still cause harm and end a career. In a new review in Translational Sports Medicine, led by Laura Mancin and Giuseppe D'Antona, with Graeme Close, Stefano Palermi and colleagues, we argue for replacing the question with a harder one: does the expected benefit outweigh the risk for this athlete, using this product, at this time?

The reason the question has to be phrased that way is strict liability. Under the World Anti-Doping Code, an athlete is responsible for any prohibited substance found in their sample, regardless of intent or source. A contaminated product can therefore produce an adverse analytical finding and an anti-doping rule violation, with disqualification, suspension, financial loss and reputational damage following from it. Intent and fault may reduce a sanction; they do not remove the responsibility. Athlete Support Personnel (physicians, dietitians, coaches and trainers) can also be implicated when they recommend, provide or facilitate the use of a high-risk product.

How large is the supplement contamination risk?

Often the assumption is made that a contaminated batch is somebody else's problem, but supplement contamination is not rare, and under strict liability the athlete carries the consequence whether or not the substance was on the label. How many supplements are contaminated? The new review does not give a single number, and the reason is worth explaining, because a headline percentage is what most people would expect from a paper like this. Large laboratory surveys have repeatedly found undeclared anabolic agents, stimulants, selective androgen receptor modulators (SARMs) and other pharmacologically active compounds in products sold as supplements. But the sampling in those surveys is often opportunistic and over-represents higher-risk categories and online sources, so the percentages they report are likely overestimations.

The true population-level contribution of contaminated supplements to anti-doping rule violations remains difficult to quantify, and a precise figure quoted without those caveats over-reads the data.

Real-world cases run into the opposite problem: by the time a violation is investigated the product may no longer be available, batch-level testing may not be performed, and athletes do not always disclose everything they took.

So the true population-level contribution of contaminated supplements to anti-doping rule violations remains difficult to quantify, and a precise figure quoted without those caveats over-reads the data. What can be said is that the risk is real, that it is not evenly distributed across products, and that it is large enough to matter clinically. That last point is the practical one: the risk can be managed by choosing differently rather than by avoiding supplements altogether.

Risk is a property of the product, not of the category

It is not binary and it is impossible to say: these are products with a problem and these are safe. However, a single-ingredient creatine monohydrate supplement that is certified has a substantially different risk profile from an uncertified multi-ingredient preworkout or a "testosterone booster". They may be sold in the same store, may even sit on the same shelf and are regulated under the same framework. In many jurisdictions regulation is very limited: the Dietary Supplement Health and Education Act of 1994 in the United States shifted substantial responsibility for safety and labelling to manufacturers rather than regulators, and similar asymmetries exist internationally.

Contamination reaches a product by more than one route. Unintentional cross-contamination occurs when manufacturing lines process multiple products, including products containing prohormones, stimulants or other pharmacologically active substances, and is made more likely by inadequate cleaning, poor raw-material control and insufficient batch testing. Intentional adulteration is also well documented, and it clusters in a predictable set of products: those marketed for rapid weight loss, pre-workout stimulation, body composition change, muscle growth, or hormonal enhancement. An active substance may be added deliberately to produce a perceptible effect without being mentioned on the label. Proprietary blends make it harder to detect, because ingredients can be listed under unfamiliar chemical names, declared in inaccurate quantities, or left off the label entirely.

Certification reduces supplement risk, it does not remove it

Third-party certification programmes such as Informed Sport, NSF Certified for Sport, the Cologne List, BSCG and NZVT test selected products or batches against lists of prohibited substances, and they do reduce the likelihood of contamination. They are a risk-minimisation tool rather than a guarantee. Certification status can change, logos can be misused, and not every manufactured batch may be tested. The practical consequence is specific: check the product and the batch number in the certifier's own database or app before use, rather than trusting the logo on the tub.

The evidence differs by supplement category, and so does the risk

Grouping supplements by evidence is familiar from the Australian Institute of Sport framework, and in the review we mapped anti-doping risk onto it. Creatine and caffeine have the most consistent evidence for selected performance outcomes. Beta-alanine, dietary nitrate and sodium bicarbonate show benefits that are real but context-specific: beta-alanine mainly for efforts of roughly one to four minutes and repeated high-intensity work, and it requires chronic loading, while sodium bicarbonate increases extracellular buffering capacity but gastrointestinal symptoms often limit its usefulness. Iron and vitamin D have clear indications when deficiency or insufficiency is documented, and both are rated lower than creatine or caffeine precisely because the performance case in replete athletes is weak. Iron supplementation in iron-replete athletes is inappropriate and may cause adverse effects, and vitamin D should follow an assessment of serum status rather than routine high-dose use.

Many recovery- and health-oriented products rest on smaller, heterogeneous studies or on indirect outcomes. Collagen or gelatin with vitamin C has a plausible mechanistic role in connective tissue remodelling when combined with appropriate loading, but the clinical evidence for injury prevention or return to play is still emerging, and probiotic effects are strain-specific and cannot be generalised across products. Magnesium, BCAA, HMB, vitamin E, prebiotics and tyrosine are promoted on mechanistic claims that exceed the evidence. Stimulants, SARMs, prohormones, peptide hormones, metabolic modulators, masking agents and diuretics have no legitimate role in evidence-based supplementation and should be avoided entirely.

One point in that table is easy to miss. A higher evidence category is not an automatic indication to supplement. Evidence that a supplement improves an outcome in some athletes is not evidence that this athlete needs it now, and efficacy alone does not justify use.

Seven questions before an athlete takes anything

The review sets out ten practical strategies, and the decision framework in Figure 1 is the order in which they are applied. Seven questions come before the product is taken. Some answers stop the process outright; others send the athlete back to fix something before going on. None of them can be traded off against a "yes" further down.

1. Is supplementation necessary? Is there a nutritional deficiency, a clinical indication, or a performance goal that diet cannot meet? If not, optimise diet and lifestyle first.

2. Is there evidence supporting use in this situation, for this outcome?

3. What is the contamination risk of this specific product? Multi-ingredient formulations, unregulated markets, "natural" or herbal products and a contamination history in the category all raise it.

4. Is the product third-party tested?

5. Has this batch been verified in the certifier's database or app, using the batch number on the tub? (always check the batch number on the certifier database! Don’t just trust a logo on a product)

6. Is use supervised by a qualified sports physician or sports dietitian, as part of an individualised plan?

7. Is the decision documented: product, brand, batch number, indication, dose and timing, start and review dates, and who advised it?

Only when all seven have a "yes" does supplementation proceed, and the remaining three strategies apply from that point on: monitor the effect, monitor for adverse effects, and review whether the original indication still holds. Nothing about that sequence eliminates risk. It reduces it, and it makes the residual risk visible.

Conclusion

Supplement use should be treated as a controlled, individualised and documented intervention rather than as casual or routine practice. The evidence is not uniform across supplement categories, the contamination risk is not uniform across products, and the athlete carries the consequence either way. If a practitioner has recommended or provided a supplement, they will be implemented too.

Certification and batch testing are analytical solutions to a problem that is partly behavioural. Athletes do not choose supplements on nutritional need alone: peer influence, coach recommendations, perceived performance pressure, sponsorship, body-image concerns and social media marketing all shape the decision, and the belief that "natural" or legally available means safe is common. Education, risk perception and organisational policy therefore have to do work that testing cannot.

This does not mean supplements should be abandoned. Used for a clear indication and sourced from verified products, several of them do exactly what athletes want them to do. The argument in the review is: the decision needs to be deliberate, justified and traceable, and it needs to be made with the same care as any other clinical decision in an athlete's programme.

References

1. Mancin L, Close GL, Jeukendrup A, Freschi M, Pugh J, Sala M, Baioccato V, Vecchiato M, D'Antona G, Palermi S. Reducing the Risk of Unintentional Doping From Supplements: A Practical Guide for Athletes and Support Teams. Translational Sports Medicine 2026; 2026:5919439. Open access: https://doi.org/10.1155/tsm2/5919439