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Summary

This scholarly review explores the efficacy and considerations of sports foods and dietary supplements for track-and-field athletes. It distinguishes between sports foods designed for nutritional goals like hydration and anabolism, and performance supplements such as caffeine, creatine, and nitrates, which have evidence-backed benefits for certain events. The authors stress the importance of a pragmatic approach, recommending that athletes only use products that are proven safe, legal, and effective, and have been personally trialled. The text also highlights risks associated with supplement use, including expense, false expectations, and potential contamination with banned substances. Ultimately, it advocates for informed decision-making in collaboration with sports nutrition professionals.

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​Sports Foods and Dietary Supplements for Optimal Function and Performance Enhancement in Track-and-Field Athletes​
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Executive Summary

This scholarly review examines the role of sports foods and dietary supplements in optimising the health, function, and performance of track-and-field athletes. While acknowledging the extensive marketing of such products, the authors emphasise the importance of a "pragmatic approach" based on strong scientific evidence for efficacy, safety, and legality. The document categorises nutritional aids into sports foods, performance supplements, and therapeutic/prophylactic aids, highlighting the limited number of performance supplements with robust evidence. It also outlines significant disadvantages, including expense, false expectancy, and the critical risk of ingesting banned substances. Ultimately, the authors advocate for individualised trials and professional guidance before incorporating any supplements into an athlete's routine.

2. Main Themes

2.1. The Foundation of Athlete Success vs. Supplements

The document stresses that "effective marketing campaigns and athlete endorsements may convince us that certain sports foods and supplements are fundamental in allowing athletes to reach their sporting goals. However, this approach is naive in understanding the true foundations of athlete success." These fundamental elements include:

• Inherent genetic predisposition.
• "Many hours of well-structured/periodised training."
• Appropriate underlying nutrition.
• Adequate sleep and recovery.
• Good overall physical and mental health. Supplements are presented as potentially useful only when these foundational elements are "all accounted for," particularly for elite athletes seeking "marginal performance gains."

2.2. Categorisation and Definition of Nutritional Aids

The review defines a dietary supplement 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."

It then broadly categorises nutritional aids:

• Sports Foods: "Specifically formulated food products that are commercially developed for use by athletes." These aim to support physiological goals such as hydration, fuelling (carbohydrate provision), anabolism (protein ingestion), and osmolality (electrolyte ingestion). While offering practical advantages in terms of convenience and specific nutrient combinations, they should not replace "everyday foods" and can be more expensive.
• Performance Supplements: Products marketed to directly enhance athletic performance. Only a "handful are supported by an evidence base that warrants consideration for trial use by athletes."
• Therapeutic Nutritional Supplements and Prophylactic Aids: Nutritional aids used to "correct a deficiency, (b) assist in the possible prevention of illness and/or injury, or (c) help in the recovery from the stress of physical workloads via an anti-inflammatory effect."

2.3. Prevalence of Supplement Use

A systematic review of 159 studies (Knapik et al., 2016) found high variability in supplement use, ranging from 4% to 62% across different supplement types. Significantly, "elite athlete cohorts (SPE male: ∼69% and SPE female: ∼71%) presented with greater rates of supplement use than their nonelite counterparts (SPE male: ∼48% and SPE female: ∼42%)." Sex differences were also observed, with females using more supplemental iron and males more protein, creatine, and vitamin E.

2.4. Evidence-Based Performance Supplements

The review identifies only five performance supplements with adequate evidence to suggest "marginal performance gains" for elite athletes:

• Caffeine:
• Benefits: "Well-established benefits for enhancing athletic performance across both endurance-based events and short-term, supramaximal tasks." Improves neuromuscular function, vigilance, alertness, and masks pain/perception of effort.
• Dosage: Typically 3–6 mg/kg of body mass (BM) ~60 min pre-exercise. Lower doses (<3 mg/kg BM) also beneficial.
• Challenges: High individual variability (influenced by genetics), requires careful planning for repeated use (e.g., multi-event competitions), potential negative side effects (nausea, anxiousness, insomnia, restlessness) at higher doses (≥9 mg/kg BM). Habitual use has "limited impact" on performance effects.
• Application to Track-and-Field (Table 3): Sprints, sustained sprints, middle distance, long distance, jumps and throws, multievents.
• Creatine Monohydrate (CM):
• Benefits: Increases muscle creatine and phosphocreatine stores, enhancing short-term, high-intensity exercise capacity (<150s, most pronounced <30s). Also aids chronic training adaptations like lean mass gains and improvements in muscular strength and power.
• Dosage: "Loading phase" of ~20g/day (4 x 5g doses) for 5-7 days, followed by a "maintenance phase" of 3-5g daily. Lower doses (2-5g/day) for ~4 weeks also effective. Co-ingestion with protein/carbohydrate can enhance uptake.
• Challenges: Potential weight gain (1-2kg) from increased water storage, which "may be counterproductive for weight-sensitive events." Unclear speculation about negation of benefits by caffeine.
• Application to Track-and-Field (Table 3): Sprints, jumps and throws, multievents.
• Nitrate (e.g., Beetroot Juice):
• Benefits: Enhances NO bioavailability, improving exercise performance (4-25% increased time to exhaustion, 1-3% increased sport-specific performance) in aerobic tasks lasting <40 mins. Also enhances Type II muscle fiber function (3-5% improvement in high-intensity efforts).
• Dosage: Acute benefits within 2-3 hours after 5-9 mmol (310-560 mg) NO3-. Chronic intake (>3 days) also beneficial.
• Challenges: Individual responsiveness, lack of response in athletes with "well-developed aerobic capacity (i.e., VO2max >60 ml/kg)." Potential for minor gastrointestinal upset. Upper limit to benefits.
• Application to Track-and-Field (Table 3): Sustained sprints, middle distance, long distance, multievents.
• β-Alanine:
• Benefits: Increases muscle carnosine content (an intracellular pH buffer), improving "tolerance for maximal exercise in the range of 30 s to 10 min" (0.2-3% performance benefits).
• Dosage: 3.2-6.4 g/day via split doses (0.8-1.6g every 3-4 hours) over 4-12 weeks.
• Challenges: Possible negative side effect of "skin paresthesia." Large interindividual variations in muscle carnosine synthesis.
• Application to Track-and-Field (Table 3): Sustained sprints, middle distance, multievents.
• Sodium Bicarbonate (NaHCO3):
• Benefits: Acts as an extracellular (blood) buffer, enhancing performance (~2%) of short-term, high-intensity sprints lasting ~60 seconds.
• Dosage: 0.2-0.4 g/kg BM. Peak blood bicarbonate levels 75-180 min post-ingestion. Split doses or serial loading proposed to minimise side effects. Co-ingestion with carbohydrate-rich meal.
• Challenges: "Potential for gut disturbances is high risk in running-based events." Reduced efficacy for efforts exceeding 10 minutes.
• Application to Track-and-Field (Table 3): Sustained sprints, middle distance, multievents.

2.5. Therapeutic Nutritional Supplements and Prophylactic Aids

• Iron: "Iron deficiency can impair hematologic adaptation, which left untreated can negatively impact on athletic performance." Correction can positively impact performance.
• Immune Support: Strenuous exercise can cause immunodepression. While some supplements appear promising (e.g., probiotics for immune function), "further intensive investigation fails to provide sufficient evidence of consistent beneficial effects." Glutamine and branched-chain amino acids have "unclear role in supporting immune function."
• Anti-inflammatory/Antioxidant: Food polyphenols (e.g., tart Montmorency cherries, highly coloured vegetables/fruit) show promise in reducing inflammatory and oxidative stress responses to strenuous exercise and aiding recovery. However, "there is currently some controversy about whether high-dose antioxidant supplementation (in the form of pills, powders, and tablets) is advisable to alleviate exercise-induced generation of reactive oxygen/nitrogen species."

2.6. Disadvantages and Risks of Supplement Use

The document highlights significant risks, categorised as:

• Risks of Labeled Content:
• Supplements "cannot necessarily all be considered safe," as regulations often don't require specific testing before market.
• "Proprietary-blend" listings are not transparent.
• Examples given of toxic substances (e.g., DMAA) leading to health issues and even death.
• Risks of Undeclared or Unlabeled Content (Contamination and Doping):
• Supplements can contain "contaminants or health hazards, such as molds, glass, or animal feces."
• Crucially for athletes: "The undeclared presence of substances that are banned under the World Anti-Doping Agency (WADA) anti-doping code." This risk is "still very much present."
• Banned substances found include stimulants, anabolic agents, SARMs, diuretics, anorectics, and β2 agonists.
• "The WADA rules of strict liability mean that the detection of a prohibited substance in an athlete’s specimen will be treated as an anti-doping rule violations, irrespective of the intentions behind it."
• Using third-party tested products helps "lower, but not completely eliminate, this risk." Avoidance of "high-risk multi-ingredient supplements promoted as preworkouts or weight loss and bodybuilding products is recommended."
• Noncontent-Related Risks:
• Any benefit of legal supplementation is "bound to be small."
• Expense: "Finite resources could have been used in other areas of the preparation of an elite athlete’s life."
• "Supplement use may be a stepping stone to taking other substances, including those prohibited by antidoping regulations."

3. Key Takeaways and Recommendations for Athletes

• Prioritise Fundamentals: Athlete success is built on genetics, structured training, proper nutrition, adequate sleep, recovery, and overall health. Supplements are marginal gains.
• Evidence is Paramount: Only consider supplements with a "strong evidence base supports their use as safe, legal, and effective."
• Individualised Trial: "Such supplements are trialed thoroughly by the individual before committing to use in a competition setting" due to individual variability and potential side effects.
• Professional Guidance: Consult qualified sports nutrition professionals, sports physicians, and sports science experts for guidance on supplement choices, dosage, and integration into training plans.
• Understand Risks: Be fully aware of the potential for undeclared banned substances and the WADA "strict liability" rule, which holds athletes responsible for any prohibited substance found in their system, regardless of intent.
• Avoid High-Risk Products: Be cautious of "proprietary-blend" supplements and avoid high-risk multi-ingredient products (e.g., pre-workouts, weight loss, bodybuilding supplements) due to high contamination risk.
• Cost-Benefit Analysis: Consider the financial cost versus the potentially small performance benefits. Many nutritional goals can be met with cheaper "everyday foods."

Quiz: Short-Answer Questions

Answer each question in 2-3 sentences.

1. What is the primary distinction between "sports foods" and "everyday foods" as described in the text, beyond their commercial formulation for athletes?
2. List the four main physiological goals that sports foods generally help to support in athletes.
3. According to the text, which five performance supplements have an adequate level of evidence to suggest marginal performance gains for elite athletes?
4. Explain why caffeine habituation has limited impact on the performance effects of caffeine, contrary to earlier beliefs about the need for caffeine withdrawal.
5. What is the main physiological mechanism by which creatine monohydrate supplementation enhances exercise capacity?
6. Describe two potential disadvantages of creatine monohydrate supplementation, particularly in the context of specific track-and-field events.
7. How does nitrate supplementation enhance exercise performance, and for which type of exercise tasks is it primarily effective?
8. What is the primary mechanism by which beta-alanine supplementation is believed to improve exercise performance, and what is a common negative side effect?
9. Explain the key difference in buffering mechanisms between beta-alanine and sodium bicarbonate supplementation.
10. What are the three main categories of risks associated with the decision to take dietary supplements?

Answer Key

1. While both can contain similar nutrients, sports foods offer the practical advantage of combining specific nutrients for a goal in a single source, and their manufacturing optimises convenience, digestibility, storage, and transport. Unlike everyday foods, they may consist of only a few nutrients, making them supplementary rather than dietary replacements.
2. The four main physiological goals supported by sports foods are: hydration (fluid ingestion), fuelling (carbohydrate provision), anabolism (protein ingestion for adaptation and recovery), and osmolality (electrolyte ingestion to replenish sweat loss).
3. The five performance supplements with adequate evidence for marginal performance gains in elite athletes are: caffeine, creatine monohydrate, nitrate/beetroot juice, $\beta$-alanine, and bicarbonate (sodium bicarbonate).
4. Caffeine habituation has limited impact because high-habitual users tend to experience similar performance benefits as those with low and moderate intakes. Earlier studies suggesting a need for withdrawal may have been measuring the reversal of negative withdrawal effects (like headache or fatigue) rather than a unique performance benefit.
5. Creatine monohydrate supplementation increases muscle creatine and phosphocreatine stores. This sustains exercise that would otherwise be limited by the inability of phosphocreatine resynthesis to keep pace with fuel demands during high-intensity, short-duration exercise.
6. Two potential disadvantages are weight gain of 1-2 kg, which can be counterproductive for weight-sensitive events like jumps and distance races, and potential interactions with other concurrently used supplements, although the literature on this for creatine and caffeine is unclear.
7. Nitrate enhances NO bioavailability, augmenting exercise performance via improved Type II muscle fibre function, reduced ATP cost of muscle force production, and increased mitochondrial respiration efficiency. It is primarily effective for tasks stressing the aerobic energy system, such as endurance events, and high-intensity efforts lasting less than 40 minutes.
8. The primary mechanism for $\beta$-alanine's performance benefit is believed to be enhanced buffering capacity due to increased muscle carnosine content. A possible negative side effect is skin paresthesia.
9. $\beta$-alanine supplementation achieves a chronic elevation in intracellular buffering capacity by increasing muscle carnosine. In contrast, sodium bicarbonate ingestion results in an acute increase in extracellular (blood) buffering capacity.
10. The three main categories of risks are: risks of labeled content (e.g., unrecognized ingredients, lack of pre-market testing, toxic substances), risks of undeclared or unlabeled content (e.g., contaminants like molds or banned WADA substances), and non-content related risks (e.g., false expectations, high expense, being a stepping stone to banned substances).

Glossary of Key Terms

• Anabolism: The metabolic processes that construct molecules from smaller units, often associated with building muscle mass or tissue repair.
• Anti-Doping Rule Violations (ADRV): A breach of the anti-doping rules set forth by bodies like the World Anti-Doping Agency (WADA), which can result in sanctions for athletes and support personnel.
• Antioxidant: A substance that inhibits oxidation, a process that can produce free radicals and damage cells.
• ATP (Adenosine Triphosphate): The main energy currency of the cell, used to power various cellular processes, including muscle contraction.
• $\beta$-alanine: A non-essential amino acid that is a precursor to carnosine, used as a supplement to increase muscle carnosine levels and enhance buffering capacity.
• Bicarbonate (Sodium Bicarbonate, NaHCO3): An alkaline salt used as a supplement to increase extracellular (blood) buffering capacity during high-intensity exercise.
• Caffeine: A stimulant known for its ergogenic effects, enhancing athletic performance across various event types by acting as an adenosine receptor antagonist.
• Carnosine: An intracellular dipeptide (composed of $\beta$-alanine and histidine) found in muscle, known for its buffering, antioxidant, and anti-inflammatory properties.
• Contaminants: Unintended or undesirable substances present in a product, which can include banned substances in dietary supplements.
• Creatine Monohydrate (CM): A nitrogenous organic acid that helps supply energy to cells, primarily muscle, by increasing phosphocreatine stores, thereby improving short-term, high-intensity exercise capacity.
• Dietary Supplement: A food, food component, nutrient, or non-food compound purposefully ingested in addition to the habitually consumed diet to achieve a specific health and/or performance benefit.
• DMAA (1,3-dimethylhexanamine): A stimulant that was previously included in some dietary supplements but is now banned by WADA and has been associated with serious health risks.
• Ergogenic Aids: Substances, practices, or phenomena that improve athletic performance.
• Gastrointestinal Distress: Unpleasant symptoms related to the digestive system, such as nausea, cramping, or diarrhoea, often experienced as a side effect of certain supplements.
• Immunodepression: A weakened state of the immune system, often temporarily experienced by athletes after strenuous exercise.
• Immunonutrition: The study and application of nutritional strategies to support or modulate the immune system, particularly in the context of exercise.
• Inadvertent Doping: An anti-doping rule violation that occurs without the athlete's intention to cheat, often due to contamination of supplements or unawareness of banned substances.
• Nitrate (NO3-): An inorganic compound, often consumed via beetroot juice, that enhances nitric oxide (NO) bioavailability, improving exercise performance by affecting muscle function and blood flow.
• Nitric Oxide (NO): A molecule that plays a crucial role in various physiological processes, including vasodilation (widening of blood vessels) and muscle function.
• Osmolality: The concentration of a solution, often referring to the balance of water and electrolytes in the body.
• Paresthesia: A burning or prickling sensation, often felt in the extremities, a common side effect of $\beta$-alanine supplementation.
• Performance Supplements: Dietary supplements specifically marketed and used with the aim of directly enhancing athletic performance.
• Phosphocreatine (PCr): A high-energy phosphate compound stored in muscle, used to rapidly regenerate ATP during short, intense bursts of activity.
• Physiological Goals (of Sports Foods): The specific bodily functions or states that sports foods aim to support, such as hydration, fuelling, anabolism, and osmolality.
• Proprietary Blend: A mix of ingredients in a supplement where the specific amounts of each ingredient are not disclosed, often raising concerns about transparency and safety.
• Sports Foods: Specifically formulated food products commercially developed for use by athletes to target nutritional goals related to training adaptation, recovery, and competition performance.
• Strict Liability: A principle in anti-doping rules stating that athletes are solely responsible for any prohibited substance found in their body, regardless of intent.
• Supramaximal Tasks: Exercise efforts that exceed an individual's maximal aerobic capacity, often short in duration and highly intense.
• Therapeutic Nutritional Aids/Supplements: Nutritional supplements used to correct a deficiency, prevent illness/injury, or aid recovery (e.g., through anti-inflammatory effects).
• VO2max (Maximal Oxygen Uptake): The maximum rate of oxygen consumption attainable during maximal exercise, an indicator of aerobic fitness.
• World Anti-Doping Agency (WADA): An international independent agency responsible for promoting, coordinating, and monitoring the fight against doping in sport.

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