Article - Impact of Melatonin Supplementation on Sports Performance and Circulating Biomarkers in Highly Trained Athletes: A Systematic Review of Randomized Controlled Trials.

Plain Language Summary

Melatonin (N-acetyl-5 methoxytryptamine) is an indolic neurohormone known for its antioxidant, anti-inflammatory, and immunoregulatory properties. Highly demanding training exponentially increases physical and biochemical demands, particularly in the skeletal muscle and the liver. This study aimed to critically review the effects of melatonin supplementation on sports performance and circulating biomarkers in highly trained athletes. This study was a systematic review of twenty-one randomised controlled trials. The dose of melatonin supplemented in the trials ranged from 5 mg to 100 mg, administered before or after exercise. Results showed that melatonin supplementation improved antioxidant status and inflammatory response. Additionally, it reversed liver and muscle damage, and moderate effects were also observed in modulating glycaemia, total cholesterol, triglycerides, and creatinine. Authors concluded that melatonin has a high safety profile. In fact, melatonin supplementation could act indirectly to improve performance by preventing tissue damage, reduce inflammation caused by reactive oxygen and nitrogen species, and restore circulating biomarkers in highly trained athletes during demanding exercises.

Expert Review

Reviewer: Chloe Steele

11th Sep 2024

Conflict of interest

None

Take home message

Diet and lifestyle modifications should always be made first to ensure that athletes have sufficient melatonin levels.
Adequate light exposure at appropriate times and specific foods which contain melatonin may help.
During periods of intense training, supplementation may be needed to reach adequate levels and to aid recovery.

Evidence category

B: Systematic reviews including RCTs of limited number

Summary review

Introduction

High-intensity exercise can disrupt inflammatory and immune processes within the body resulting in inflammation, poor immune function, and poor recovery.
Melatonin is a neurohormone that has anti-inflammatory and antioxidant properties, and has the potential to be of benefit to recovery following strenuous exercise.
This systematic review of randomised control trials aimed to determine the effect of melatonin on sports performance and circulating health biomarkers.

Methods

This was a systematic review of randomised control trials (RCTs).
The study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.
Studies that were included looked at the use of melatonin by trained sports professional and athletes.

Results

21 RCTs were included in the review.
Melatonin doses ranged from 5mg to 100mg in the studies.
Melatonin was administered either acutely or for periods of 3 to 30 days pre and post exercise.
None of the studies were rated low risk of bias.
Seven studies had a high risk of bias.
There was a high degree of heterogeneity, which prevented a meta-analysis being performed.
The study showed that melatonin supplementation had some effect on white blood cell count levels and immunoglobulins but results were conflicting.
Moderate effects were seen on blood glucose, cholesterol, triglycerides, and phospholipids but did not affect high density lipoprotein or low-density lipoprotein.
Improvements were seen in antioxidant status and inflammation.
Reversal of kidney and liver damage was reported following supplementation.
Promising effects were seen on sports performance with some studies reporting improvements in aerobic capacity, agility, and sprint performance.
No effects were apparent on hormonal response of cortisol, testosterone, or growth hormone.
No adverse effects were seen following melatonin supplementation.

Conclusion

Melatonin supplementation may mitigate some of the damaging effects of extreme exercise.
However, it is unclear as to how this might occur.

Clinical practice applications

Sufficient melatonin levels may be necessary in highly trained athletes.
This may limit inflammation and oxidative stress and help prevent tissue damage and aid recovery.
During periods of intense training or when quick recovery is needed, melatonin supplementation may be of benefit.

Considerations for future research

More studies on the mechanisms through which melatonin may be supporting athletic performance and preventing liver and kidney damage are needed.
Studies on the effects of melatonin on mitochondrial function may be of benefit.

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Abstract

Melatonin (N-acetyl-5 methoxytryptamine) is an indolic neurohormone that modulates a variety of physiological functions due to its antioxidant, anti-inflammatory, and immunoregulatory properties. Therefore, the purpose of this study was to critically review the effects of melatonin supplementation in sports performance and circulating biomarkers related to the health status of highly trained athletes. Data were obtained by performing searches in the following three bibliography databases: Web of Science, PubMed, and Scopus. The terms used were "Highly Trained Athletes", "Melatonin", and "Sports Performance", "Health Biomarkers" using "Humans" as a filter. The search update was carried out in February 2024 from original articles published with a controlled trial design. The PRISMA rules, the modified McMaster critical review form for quantitative studies, the PEDro scale, and the Cochrane risk of bias were applied. According to the inclusion and exclusion criteria, 21 articles were selected out of 294 references. The dose of melatonin supplemented in the trials ranged between 5 mg to 100 mg administered before or after exercise. The outcomes showed improvements in antioxidant status and inflammatory response and reversed liver damage and muscle damage. Moderate effects on modulating glycemia, total cholesterol, triglycerides, and creatinine were reported. Promising data were found regarding the potential benefits of melatonin in hematological biomarkers, hormonal responses, and sports performance. Therefore, the true efficiency of melatonin to directly improve sports performance remains to be assessed. Nevertheless, an indirect effect of melatonin supplementation in sports performance could be evaluated through improvements in health biomarkers.