Why protein powders can secretly cause doping bans

By Vijay Kumar MalesuReviewed by Lauren HardakerOct 9 2025

A review in Nutrients uncovers how tainted protein powders and performance supplements can sabotage honest athletes, revealing the hidden chemistry, clever masking tactics, and urgent safeguards needed to keep sport truly clean.

Study: Adulteration of Sports Supplements with Anabolic Steroids—From Innocent Athlete to Vicious Cheater. Image credit: AntonSAN/Shutterstock.com

In a recent review published in Nutrients, a group of authors examined current evidence on adulteration of dietary supplements (DS) with testosterone (T) and other anabolic steroids, outlined patterns of non-medical steroid use, described detection technologies and masking strategies, and recommended protective measures for athletes and clinicians.

Background

Surveys across sports show that some “performance” supplements carry undeclared, pharmacologically active ingredients that can turn an otherwise compliant test result into a positive finding. Athletes use DS to supplement nutrition gaps, recover from injury, or gain a lawful edge, especially when training loads increase. Yet products may be contaminated or deliberately spiked with T analogs and prohormones that promise faster gains than protein alone.

Studies cited in the review found contamination in up to half of the tested supplements, highlighting the scale of the issue. Beyond bans and reputational harm, users face liver strain, lipid disturbances, mood changes, and endocrine suppression. Families, teams, and careers bear the consequences. Clearer screening, smarter choices, and routine verification are needed to prevent unintentional doping.

Scope and methods of the review

This narrative review examines two perspectives: athletes who unknowingly ingest a tainted product, and a cheating athlete who manipulates biology and tests. It maps T biosynthesis from cholesterol, the downstream metabolites used in anti-doping screens, and the analytical techniques that detect abuse.

Evidence spans reviews, original studies, case reports, and World Anti-Doping Agency (WADA) technical documents, emphasizing detection in urine, and emerging use in hair that is being researched but not yet validated by WADA for official testing, with chromatography and mass spectrometry at the core.

Why are supplements getting adulterated, and who pays?

Protein-centric DS are heavily marketed for visible changes in strength and muscle. Because legal nutrition produces gradual gains, some manufacturers illicitly add anabolic steroids or prohormones to produce faster, more noticeable effects and attract positive attention.

Labels often fail to disclose these additions, meaning athletes face strict liability penalties if routine testing returns a positive result. The over-the-counter (OTC) status of these products can also give users a false sense of safety. The consequences can be both personal, such as sanctions and loss of income, and medical, ranging from liver toxicity, acne, hormonal imbalance, and disrupted lipid profiles, all of which erode public trust in sport.

Non-Therapeutic steroid use patterns you’ll encounter

Real-world misuse rarely follows medical protocols. “Cycling” alternates six to twelve weeks “on-cycle” with longer “off-cycle” breaks; “blast and cruise” keeps maintenance doses between high-dose phases to prevent regression; “stacking” combines multiple agents at lower doses to chase additive effects.

Post-cycle therapy commonly adds human chorionic gonadotropin (HCG), aromatase inhibitors (for example, anastrozole, letrozole, exemestane), and antiestrogens (for example, tamoxifen, clomiphene) to hasten hypothalamic-pituitary-gonadal recovery and reduce estrogenic side effects. Psychological drivers like perfectionism, athletic identity, and social pressure reinforce patterns and escalate dosages.

How do laboratories detect abuse?

Modern testing pairs gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), often complemented by isotope ratio mass spectrometry (IR-MS).

The steroidal module of the Athlete Biological Passport (ABP) monitors urine concentrations of T, epitestosterone (E), androsterone (A), etiocholanolone (ETIO), 5-alpha-androstane-3-alpha,17-beta-diol (5-α-ADIOL), and 5-beta-androstane-3-alpha,17-beta-diol (5-β-ADIOL), plus key ratios, classically the T/E ratio. IR-MS uses carbon-13/carbon-12 signatures to distinguish endogenous from plant-derived, semisynthetic sources typical of exogenous steroids. Together, these tools widen the net when single metrics (for example, T/E alone) would miss sophisticated doping.

Masking agents and workarounds: What changes in the profile?

Cheaters exploit biology and pharmacology to hide in plain sight. Dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT) can alter downstream metabolites without predictably lifting T/E. Co-administration of E may “normalize” an elevated T/E.

Luteinizing hormone (LH) or HCG stimulates endogenous T, again blunting T/E changes. Finasteride or dutasteride (5-alpha-reductase inhibitors) shift steroid profiles by reducing DHT-pathway metabolites; aromatase inhibitors suppress conversion to estradiol, limiting gynecomastia and nudging ratios.

Probenecid impairs renal excretion of glucuronidated steroids, lowering urinary concentrations below detection; diuretics dilute analytes. Azole antifungals (for example, ketoconazole, miconazole) inhibit steroidogenesis, decreasing T output and affecting marker ratios. Robust screening therefore quantifies multiple metabolites and ratios and directly targets masking agents.

Practical safeguards for innocent athletes and clinicians

First, treat every DS like a potential exposure. Favor certified batches from programs that test for WADA-prohibited substances; avoid high-risk, novelty, or “hard-gainer” blends and black-market imports.

Before major competitions, lock down a “clean list” with the team physician and sports dietitian; keep photos of labels and lot numbers. If a new product is unavoidable, consider pre-use screening where feasible: capillary electrophoresis (CE), ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS), or surface-enhanced Raman spectroscopy (SERS) can flag adulteration beyond classic high-performance liquid chromatography (HPLC).

Educate athletes on strict liability and help them recognize potential signs of androgen exposure, such as acne, mood shifts, and altered libido. Coordinate mental-health support since the review notes that psychological factors such as stress, anxiety, and perfectionism often precede risky supplement or steroid use.

Where is detection heading?

Because masking can outpace single-analyte assays, multi-modal approaches are expanding. Hair testing extends detection windows (months), though WADA does not currently accept it for anabolic steroids.

Research into microRNA (miRNA) signatures of organ stress (cardiac, renal, hepatic) aims to identify the biological “fingerprint” of chronic steroid exposure that are more difficult to conceal. Genotype-aware panels (for example, uridine diphospho-glucuronosyltransferase 2B17 deletion) and combined blood-plus-urine workflows may further reduce false negatives. Analytical diversity- GC-MS, LC-MS, IR-MS- plus broader biomarker sets is emphasized in the review as the path toward closing analytical loopholes.

Conclusions 

Adulterated DS can turn a compliant competitor into a sanctioned “cheater,” while determined dopers exploit endocrine pharmacology and masking agents to evade simple screens.

The solution requires multiple coordinated steps: athlete education and certified DS sourcing; clinician-led product vetting and documentation; and laboratory strategies that cross-check across metabolites, ratios, and isotope signatures within the WADA ABP. Expanding analytics (UHPLC-QTOF-MS, IR-MS) and exploring miRNA and genotype-aware markers may further improve detection and stay ahead of emerging doping tactics.

Ultimately, protecting honest athletes while deterring fraud restores fairness and keeps performance gains anchored in training, recovery, and evidence-based nutrition, not undeclared pharmacology or analytical blind spots.

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