Pre-workout supplements tied to very short sleep in teens and young adults, University of Toronto study shows

Table of Contents

1. Key Highlights:
2. Introduction
3. What the Canadian study found
4. What’s actually in pre-workout supplements?
5. How stimulants disrupt sleep physiology
6. Why the effect is especially worrisome in adolescents and young adults
7. Marketing, accessibility and social drivers behind pre-workout use
8. Practical guidance for clinicians, parents and young users
9. Safer product choices and training strategies
10. Regulatory oversight and labeling challenges
11. Real-world examples: product cases and adverse events
12. Research gaps and where science should go next
13. Communication and education strategies that work
14. Steps users can take immediately
15. Broader implications for public health and sport
16. FAQ

Key Highlights:

• Young people (ages 16–30) who used pre-workout supplements in the past year were more than twice as likely to sleep five hours or less per night than non-users.
• High caffeine and stimulant content in many pre-workout formulas—ranging from about 90 mg to over 350 mg per serving—likely explains much of the association; experts recommend avoiding these products 12–14 hours before bedtime.

Introduction

A growing slice of gym culture now begins not with a warm-up but with a scoop. Pre-workout supplements—powders and ready-to-drink formulas promising sharper focus, bigger lifts, or longer endurance—have become a routine for many adolescents and young adults. A new analysis led by researchers at the University of Toronto connects that habit with a sharp increase in extremely short sleep duration: users were more than twice as likely to report sleeping five hours or less per night.

That level of sleep restriction carries consequences for mood, learning, growth and long-term health. The study draws attention to a conversation that has so far been muted: fitness products marketed as benign performance enhancers can carry stimulant loads that undermine sleep, particularly when used by people whose sleep needs remain high. The research authors and health professionals are urging clearer consumer information and more proactive counseling by clinicians, while recommending practical steps—chiefly, avoiding pre-workout supplements within 12 to 14 hours of planned sleep.

The following report unpacks the study’s findings, explains what’s inside popular pre-workout products, explores how stimulants interact with sleep, outlines the potential short- and long-term harms of chronic short sleep during adolescence and young adulthood, and offers practical guidance for clinicians, parents and young athletes.

What the Canadian study found

The analysis used data from the Canadian Study of Adolescent Behaviors and focused on participants aged 16 to 30. Researchers asked respondents whether they had used pre-workout supplements in the previous year and collected self-reported sleep duration. After adjusting for demographic and behavioral factors, users of pre-workout supplements were more than twice as likely to report sleeping five hours or less per night compared with non-users.

Five hours of sleep per night falls well below recommended targets. National sleep guidelines generally advise adolescents to obtain eight to ten hours nightly, while young adults should aim for seven to nine hours. Short sleep—especially persistent short sleep—during these developmental windows is associated with impaired cognitive performance, mood disorders, poorer school or work performance, and physiological effects ranging from slowed growth in adolescents to metabolic changes.

The study does not establish a direct causal link, but the observed association was strong and consistent. Lead author Kyle T. Ganson, an assistant professor at the Factor-Inwentash Faculty of Social Work at the University of Toronto, framed the findings as a call to action: many of these products contain high levels of caffeine and stimulant-like ingredients that plausibly interfere with sleep. The researchers recommend that health professionals discuss supplement use with their young patients and suggest practical advice such as avoiding pre-workout products for 12 to 14 hours before bedtime.

What’s actually in pre-workout supplements?

Pre-workout supplements vary widely between brands and flavors, but several common components recur:

• Caffeine. Many formulas contain caffeine in amounts that range from roughly 90 mg to more than 350 mg per serving. A standard cup of coffee contains about 100 mg of caffeine, while a can of cola contains roughly 35 mg. Because companies use different serving sizes and sometimes expect users to take more than one serving, actual intake can exceed the amount listed.
• Stimulant analogues and alkaloids. Ingredients such as synephrine, yohimbine and, historically, DMAA (1,3-dimethylamylamine) have appeared in some products. DMAA has been banned or restricted in many jurisdictions after reports of serious adverse events, but other stimulant compounds still appear in products or in blends labeled as proprietary.
• Beta-alanine and creatine. These do not act as stimulants but are often included to reduce muscle fatigue or support muscle performance. Beta-alanine can produce a tingling sensation (paresthesia) that some users equate with efficacy.
• Nitric oxide precursors. Citrulline and arginine aim to increase blood flow and “pump,” but their effects on central nervous system arousal are indirect.
• Proprietary blends. Many products use proprietary or “proprietary” blends that obscure exact quantities of active ingredients, letting companies list components without specifying milligram amounts for each.

Popular brand names that have become part of the mainstream fitness market—Bang!, Jack3D, and C4—were specifically mentioned in the recent reporting of the study. Their formulas differ, but all highlight the point: marketing emphasizes immediate performance benefits, while stimulant content can be substantial.

How stimulants disrupt sleep physiology

Caffeine and other stimulants act on the central nervous system to increase alertness, delay the perception of fatigue and enhance aspects of cognitive and physical performance. Those effects come at a cost for sleep.

• Adenosine blockade. Caffeine works primarily by blocking adenosine receptors. Adenosine accumulates during wakefulness and promotes sleepiness. By occupying adenosine receptors, caffeine reduces sleep pressure and delays the onset of sleep.
• Half-life and residual effects. The biological half-life of caffeine in adults is typically about five to six hours, but it varies considerably by individual. For some people, especially younger users or those with slower metabolic clearance, stimulant effects can persist far longer than expected. That explains recommendations to avoid caffeine 12 to 14 hours before bedtime in order to prevent residual arousal.
• Increased sleep latency and decreased sleep duration. Stimulants delay sleep onset and reduce total sleep time when taken sufficiently close to bedtime. Even if a person falls asleep, stimulant exposure can fragment sleep architecture, reducing slow-wave and REM sleep, which are essential for physical recovery and memory consolidation.
• Stimulant stacking and cumulative exposure. Users may not realize that caffeine sources add up: a pre-workout scoop plus a coffee, energy drink, or caffeinated soda during the day can push total intake into levels associated with insomnia, jitteriness, or cardiovascular symptoms.
• Interaction with circadian rhythm. Nighttime stimulant use can shift circadian timing indirectly. Repeated late-day stimulant consumption conditions wakefulness at hours the biological clock expects sleep, reinforcing delayed sleep patterns and potentially contributing to chronic short sleep.

Young bodies and brains are still developing signal pathways for sleep and arousal. Adolescents and some young adults already face tendencies toward later sleep timing driven by biological changes in puberty; introducing exogenous stimulants can compound the problem, pushing sleep even later and truncating total duration.

Why the effect is especially worrisome in adolescents and young adults

The ages covered by the study—16 to 30—span a period of ongoing brain development and significant life demands. Sleep plays a foundational role across multiple domains:

• Cognitive performance and learning. Sleep supports consolidation of new memories and learning. Adolescents and students of any age require consistent sleep to perform well academically. Even modest reductions in nightly sleep duration erode attention, working memory and decision-making.
• Mental health. Depression and anxiety are strongly linked to insufficient sleep. The relationship is bidirectional: poor sleep can precipitate mood disorders, and mood disorders can disrupt sleep. Studies repeatedly show higher rates of mood disturbances among young people with chronic short sleep.
• Physical growth and metabolism. Adolescence remains a period of physical maturation. Sleep influences hormonal cascades that regulate growth, appetite and metabolic balance. Chronic sleep restriction associates with weight gain, insulin resistance, and dysregulated appetite hormones.
• Risk-taking and substance use. Sleep loss increases impulsivity and risk-taking behaviors. That interacts with environments where supplement use, alcohol consumption or other substance use may be present.
• Athletic performance and recovery. While pre-workouts aim to boost training, insufficient sleep undermines recovery, neuromuscular function and adaptation to training. Gains achieved through enhanced training sessions may be blunted if recovery is inadequate.

The combination of heavy stimulant use and chronic sleep restriction may therefore be counterproductive: short-term priming for a high-intensity session may come at the expense of longer-term physiological and psychological recovery.

Marketing, accessibility and social drivers behind pre-workout use

Pre-workout supplements have become culturally normalized within fitness communities for several reasons:

• Performance narratives. Advertising and influencer marketing frame pre-workouts as tools for superior performance—bigger lifts, sharper focus, better endurance. That messaging appeals to novices and experienced lifters alike. Social media amplifies before-and-after narratives and creates peer pressure to use the same products.
• Immediate reinforcement. Unlike supplements intended for weeks-long loading phases, pre-workouts provide an immediate, perceivable change: an energy surge, tingling sensations, or heightened focus. Those immediate effects reward continued use.
• Accessibility. Many pre-workout products are sold in gyms, supplement stores and online, often without age checks or medical guidance. Young consumers can access them with minimal gatekeeping.
• Misperception of safety. Pre-workouts are marketed as “fitness” products rather than psychoactive or pharmacological agents. That framing encourages a view of these substances as benign, particularly among adolescents and young adults.
• Stacking culture. Enthusiasts may combine pre-workout powders with other supplements, energy drinks or stimulants to intensify effects, sometimes disregarding cumulative stimulant loads.

Understanding the market forces explains why public health messaging that focuses narrowly on caffeine content may be insufficient. Effective responses require addressing how these products are presented and sold, particularly to younger consumers.

Practical guidance for clinicians, parents and young users

The research team recommended that pediatricians, family physicians and social workers routinely ask young patients about supplement use. That recommendation is practical and actionable. Clinicians can integrate a few simple questions and concrete counseling points into routine care:

• Ask directly. Providers should ask patients whether they use pre-workout products, the brand and typical timing relative to sleep. Adolescents may not volunteer this information unless prompted.
• Quantify intake. Encourage patients to track all sources of caffeine over 24 hours—coffee, tea, soda, energy drinks, chocolate and supplements. Many underestimate their total daily intake.
• Recommend timing. Avoiding pre-workout supplements for 12 to 14 hours before the intended bedtime reduces the likelihood of residual stimulant effects. For someone who goes to bed at 11 p.m., that means avoiding stimulant-containing supplements after the previous morning or early afternoon, depending on individual sensitivity.
• Counsel about dosing. Warn against taking multiple scoops or mixing products. Many adverse events stem from using more than the recommended serving size or combining multiple stimulant-containing products.
• Promote alternatives. For those seeking a pre-workout edge but concerned about sleep, consider caffeine-free options or non-stimulant strategies: proper fueling with carbohydrates and protein, dynamic warm-ups, strategic hydration, and structured sleep routines.
• Address underlying sleep hygiene. Counsel on consistent sleep schedules, limiting electronic device use near bedtime, and creating a dark, cool sleep environment.
• Consider underlying causes of poor sleep. If sleep remains inadequate despite reducing stimulant exposure, evaluate for insomnia, delayed sleep phase disorder, mood disorders or other medical issues.
• Educate parents and guardians. For adolescents living at home, parents should be advised to check supplement packaging and model healthy use of caffeine-containing products.

Clinicians will need practical scripts: “Do you use any powders or drinks before exercise?” followed by “What brand and how late in the day do you take it?” Those short questions can open a preventive conversation.

Safer product choices and training strategies

Young athletes and fitness enthusiasts who want to preserve sleep while supporting performance have several options:

• Choose low-caffeine or caffeine-free pre-workout blends. Some products explicitly market low or no caffeine alternatives that contain beta-alanine, creatine, citrulline or other non-stimulant ingredients aimed at performance without central nervous system arousal.
• Time workouts strategically. When possible, schedule high-intensity sessions earlier in the day so that any stimulant taken has time to clear before bedtime. Morning or early afternoon training reduces the conflict between stimulant use and sleep.
• Use food and hydration. A carbohydrate-and-protein snack 60–90 minutes before training can provide energy without stimulant side effects. Proper hydration and a light warm-up also improve performance.
• Start with low doses. If choosing a stimulant-based product, start at half the recommended serving to assess tolerance and sensitivity before increasing. Never combine with energy drinks or other concentrated caffeine sources.
• Read labels carefully. Be wary of proprietary blends that conceal ingredient amounts. Look for products that list specific milligrams per ingredient and avoid ones that hide quantities.
• Monitor side effects. Jitteriness, palpitations, gastrointestinal upset, excessive anxiety or insomnia are signs to stop use and seek medical advice.

These steps help balance short-term training goals with the long-term need for adequate recovery.

Regulatory oversight and labeling challenges

Dietary supplements occupy a unique regulatory space in many countries. In Canada and the United States, pre-workout products are often regulated differently than prescription drugs. This legal framework allows products to enter the market with variable oversight of ingredients and labeling.

Two regulatory concerns stand out:

• Transparency of ingredients and dosage. Proprietary blends and vague labeling make it difficult for consumers to know how much of each stimulant they ingest. Without precise mg listings, users cannot accurately aggregate caffeine exposure across products.
• Emerging or novel stimulants. Manufacturers sometimes introduce novel compounds or analogues that have not been rigorously studied in young populations. The historical example of DMAA illustrates risks: when evidence accumulated linking the compound to adverse cardiovascular events and deaths, regulators acted to limit its use. Similar episodes can recur when new stimulants reach the market without comprehensive safety data.

Calls for stronger oversight focus on mandatory disclosure of stimulant content, clearer serving information, and age-appropriate warnings. Some public health advocates argue for restricting marketing aimed at minors and for clearer labeling that alerts consumers to recommended daily caffeine limits and the recommended time gap between intake and bedtime.

Until regulatory systems adapt, consumers bear the burden of vetting products. Health-care providers and educators can fill that gap with evidence-based guidance tailored to young people.

Real-world examples: product cases and adverse events

Several episodes in recent years illustrate the spectrum of risks associated with stimulant-containing fitness supplements:

• DMAA controversies. DMAA appeared in some pre-workout products and was linked to serious adverse cardiovascular events. Regulatory authorities in multiple countries moved to restrict or ban DMAA once case reports and toxicological evidence mounted. That case demonstrates how stimulant compounds added for perceived performance benefits can carry outsized health risks.
• Overdose and stacking incidents. Emergency departments report cases where users consume multiple scoops of pre-workout powder, combine supplements with energy drinks or take pre-workouts in the context of other stimulant medications. The resulting stimulant overload can cause palpitations, hypertension, anxiety attacks or worse.
• Consumer misunderstandings. Marketing that emphasizes “natural” or “clinically tested” can mislead consumers about safety. Natural-origin stimulants are not inherently safe simply because of their source.

These real-world events underscore the need for vigilance. They also highlight that while many users experience no immediate harm, a subset will face significant health consequences—particularly when products are misused or combined with other stimulants.

Research gaps and where science should go next

The University of Toronto analysis establishes a meaningful association, but several questions merit follow-up research:

• Causality and directionality. Cross-sectional associations cannot definitively prove that pre-workout use causes short sleep. Longitudinal studies tracking supplement use and sleep patterns over time would help clarify directionality.
• Dose–response relationships. How does the amount of caffeine or specific stimulants correlate with the degree of sleep loss? Precise measurement of intake is essential to answer this.
• Differential vulnerability. Are adolescents more vulnerable to stimulant-induced sleep disruption than older young adults? Genetic factors, sex differences, and individual metabolism could moderate effects.
• Broader health outcomes. Research should examine downstream consequences of combined stimulant use and short sleep on academic outcomes, mental health, cardiometabolic markers and athletic performance.
• Population-level exposure. Better surveillance of supplement use among minors and university students would inform policy and targeted education.

Answers to these questions would guide clinicians, regulators and educators in shaping recommendations that balance performance goals with health priorities.

Communication and education strategies that work

Preventive messages about stimulant-containing supplements should avoid scaring young people and instead focus on clear, practical information:

• Normalize questions in clinical encounters. When clinicians routinely ask about supplement use, young patients are more likely to disclose and receive guidance.
• Use comparative framing. Explaining how a single serving of certain pre-workouts can equal multiple cups of coffee or several cans of cola helps users intuit the magnitude of stimulant exposure.
• Show concrete trade-offs. Emphasize how improved gym performance may be offset by poorer recovery if sleep is chronically inadequate.
• Involve peers and coaches. Athletic coaches, trainers and gym staff often shape supplement culture. Equipping those influencers with accurate information multiplies the reach of safe-practice messages.
• Digital outreach where young people are. Educational campaigns on social platforms and streaming services can meet users where marketing currently exerts influence.

Clear, consistent messaging that respects young people’s autonomy while providing actionable steps will likely be more effective than admonitions alone.

Steps users can take immediately

For readers who use pre-workout supplements or are considering them, the following checklist offers immediate, practical steps:

• Audit your caffeine intake. List all sources of caffeine across a typical day and calculate total milligrams.
• Read the label. Check whether the product lists milligrams for caffeine and other stimulants. Avoid products that hide quantities behind proprietary blends.
• Time your intake. Keep stimulant-containing pre-workouts at least 12–14 hours away from planned sleep. For many, this means reserving such products for morning training sessions or choosing caffeine-free alternatives for evening workouts.
• Start low. Begin with the smallest effective dose; don’t assume you need a full scoop to get benefit.
• Avoid stacking. Do not combine with energy drinks, multiple supplements or other high-caffeine sources.
• Monitor sleep and mood. Keep a simple sleep diary for two weeks to see whether supplement use correlates with delayed sleep or daytime sleepiness.
• Talk to a clinician if you have health conditions. Those with hypertension, cardiac conditions, anxiety disorders or sleep disorders should consult a physician before using stimulant-containing products.

These steps help reduce immediate risk while preserving the option to use performance aids when appropriate.

Broader implications for public health and sport

The intersection of supplement marketing, youth culture and physiological vulnerability raises important public health questions. If a sizable proportion of adolescents and young adults are repeatedly exposed to high stimulant loads that shorten sleep, the downstream burden could include increased rates of mood disorders, impaired academic performance and worsened cardiometabolic risk profiles.

Sporting organizations and educational institutions may need to examine guidance for athletes. Coaches and athletic trainers play crucial roles in shaping safe practices. Schools and universities could incorporate basic supplement literacy into health education, helping students make informed choices.

Regulators will face pressure to balance consumer freedom with protection. Policies that require transparent labeling of stimulant content, restrict marketing to minors and mandate clear warnings about sleep disruption would target the heart of the problem. Until such measures are in place, clinicians, parents and educators must act as front-line safeguards.

FAQ

Q: How strong is the evidence that pre-workout supplements cause short sleep? A: The University of Toronto study found a strong association: users were more than twice as likely to report sleeping five hours or less per night. The study is observational and does not prove causation, but the biological plausibility—driven mainly by high caffeine and stimulant content—supports a likely causal contribution in many cases.

Q: How much caffeine is in pre-workout supplements? A: It varies widely. The study and product labels show a range roughly from 90 mg to more than 350 mg per serving. Differences in serving size and user behavior (e.g., taking more than one serving) can push intake higher.

Q: Why 12 to 14 hours as a recommended gap before bedtime? A: Caffeine’s effects can persist for many hours. While the average half-life is five to six hours, residual physiological effects can occur later. A 12- to 14-hour window reduces the chance that stimulant levels remain high enough to interfere with sleep onset and sleep quality.

Q: Are there safer pre-workout options? A: Yes. Some pre-workout products are low- or no-caffeine and emphasize non-stimulant ingredients like citrulline, creatine and beta-alanine. Non-pharmacological strategies—adequate nutrition, hydration, warm-ups and sleep—also support performance without risking sleep disruption.

Q: Can pre-workout supplements stunt growth in adolescents? A: There is no direct evidence that typical pre-workout use stunts growth. However, chronic sleep restriction during adolescence can impair growth-related hormonal processes. Because pre-workouts can contribute to short sleep, they may carry indirect risk to growth by shortening sleep duration.

Q: Should parents be worried if their teenager uses pre-workout supplements? A: Parents should be informed. Talk with the teenager about what product they use, examine the label, and ask about timing and dose. If a teen is regularly sleeping five hours or less, reducing or eliminating stimulant-containing supplements is a sensible first step.

Q: Are these products regulated for safety? A: Supplements are regulated differently from prescription drugs in many jurisdictions. That can result in variable oversight of ingredient disclosure and limited pre-market safety testing. Transparency around stimulant content and clearer consumer warnings would improve safety.

Q: What if a young athlete relies on pre-workouts for competitive advantage? A: Discuss alternatives with coaches and trainers. For many athletes, scheduling training earlier, optimizing nutrition, and using non-stimulant performance aids can maintain or improve performance without compromising sleep. If stimulant use continues, careful timing and dosing are essential.

Q: How can clinicians incorporate these findings into practice? A: Ask routine screening questions about supplement use, quantify total caffeine intake, counsel on timing (12–14 hours before bedtime), advise on dosing and stacking risks, and evaluate persistent sleep problems for medical causes.

Q: Where can I learn more? A: Start with trusted health-care providers and reputable sleep medicine resources. Product labels and third-party testing services can offer specifics on ingredient content. For population-level findings, look for peer-reviewed publications and official guidance from pediatric and sleep medicine associations.

The rapid rise of pre-workout supplements among young people has yielded immediate performance benefits for some users, but the University of Toronto study exposes a trade-off that deserves greater attention: routine stimulant consumption that undermines sleep during a developmental window when sleep matters most. Addressing that trade-off requires clear, practical advice, better product transparency and more proactive conversations among clinicians, coaches, parents and young athletes.