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Impact of Melatonin Supplementation on Sports Performance and Circulating Biomarkers in Highly Trained Athletes: A Systematic Review of Randomized Controlled Trials.
Celorrio San Miguel, AM, Roche, E, Herranz-López, M, Celorrio San Miguel, M, Mielgo-Ayuso, J, Fernández-Lázaro, D
Nutrients. 2024;16(7)
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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
Conflicts 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:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
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.
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.
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The NED Journal - Male Health, ADHD and Neurodiversity, Stress and Adrenals
Issue 2_December 2023 Peer-reviewed expert reviews and clinical insights from the Nutrition Evidence Editorial Board and Expert Review Panel
2024
Abstract
In this 2nd edition of the NED Journal, you can read some of the latest expert insights on male health, ADHD and neurodiversity, and stress and adrenals. This NED Journal transforms the science to enable individualised science-based clinical decision making, with 14 peer-reviewed expert reviews. The NED Journal supports BANT members and other integrative and personalised medicine practitioners with their evidence-based practice.
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The efficacy of exogenous melatonin supplement in ameliorating irritable bowel syndrome severity: A meta-analysis of randomized controlled trials.
Chen, KH, Zeng, BY, Zeng, BS, Sun, CK, Cheng, YS, Su, KP, Wu, YC, Chen, TY, Lin, PY, Liang, CS, et al
Journal of the Formosan Medical Association = Taiwan yi zhi. 2023;122(3):276-285
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Irritable bowel syndrome (IBS) is characterised by abdominal distension, change in stool consistency, sensation of incomplete evacuation, or pain relieved with defecation. This study's aim was to provide more evidence and directly address the efficacy of exogenous melatonin supplement in improving IBS severity. This study was a meta-analysis of four randomised controlled trials with a total of 115 participants. Results showed that daily melatonin supplement was associated with significantly better improvement in overall IBS severity, IBS pain severity, and quality of life, but not in abdominal distension or sleep quality. Furthermore, melatonin supplement was not associated with a significantly different safety profile compared to placebo. Authors concluded that their findings provided evidence for the potential benefit of exogenous melatonin supplementation in IBS management, including overall IBS severity, IBS pain severity, and quality of life.
Abstract
BACKGROUND Irritable bowel syndrome (IBS) was found in 11% of the general population worldwide. The current pharmacologic management of IBS was unsatisfactory, and it was accompanied by a number of adverse events. Melatonin was found to play an important role in gastrointestinal smooth muscle motility. Dysregulation of endogenous melatonin secretion has been found in IBS patients. Exogenous melatonin supplement has become one alternative treatment for IBS, but the evidence is inconclusive. The current meta-analysis sought to determine the efficacy of exogenous melatonin supplement in improving IBS severity in IBS patients. METHODS We included randomized controlled trials (RCTs) that investigated the efficacy of exogenous melatonin supplement in ameliorating IBS severity in IBS patients. This meta-analysis was conducted using a random effects model. The primary target outcomes were changes in IBS severity associated with melatonin or placebo. RESULTS This meta-analysis of 4 RCTs and 115 participants revealed that exogenous melatonin supplement was associated with significantly better improvement in overall IBS severity than placebo (k = 4, Hedges' g = 0.746, 95% confidence intervals = 0.401-1.091, p < 0.001). The subgroup without concurrent medication had the same result (p < 0.001). In addition, exogenous melatonin supplement was also associated with significantly better improvement in IBS pain severity (p < 0.001) and quality of life (p = 0.007) than placebo, but not in abdominal distension (p = 0.111) or sleep quality (p = 0.142). Finally, melatonin was associated with similar safety profiles with placebo. CONCLUSION This meta-analysis provides evidence for the use of exogenous melatonin in IBS patients to ameliorate overall IBS severity, IBS pain severity, and quality of life. TRIAL REGISTRATION PROSPERO CRD42021269451.
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How to fix sleep schedules naturally: 6 tips to help
Dr Ruscio is a Doctor of Natural Medicine, Doctor of Chiropractic, clinical researcher and author. His podcast, Dr Ruscio Radio presents cutting edge information in health, nutrition and functional medicine distilled into practical advice that can be used to improve our health.
2023
Abstract
Dr Ruscio explores the factors that may contribute to poor quality sleep and how this in turn can impact our health. He reviews six tips to optimise our sleep schedule and work in accordance with our natural circadian rhythm.
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Dietary supplements in neurological diseases and brain aging.
Naureen, Z, Dhuli, K, Medori, MC, Caruso, P, Manganotti, P, Chiurazzi, P, Bertelli, M
Journal of preventive medicine and hygiene. 2022;63(2 Suppl 3):E174-E188
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The rate of neurodegenerative diseases (ND) is increasing at a concerning rate. The condition is characterized by the progressive decline of neuron function in the brain, eventually leading to cognitive impairment and motorneuron disorders. This process appears to be mediated by the complex interplay of factors. The brain is extremely sensitive to oxidative stress, and oxidative stress and inflammation of the nervous tissue appear to be a common denominator in all neurodegenerative diseases. One of the challenges of ND for prevention as well as treatment and treatment development, is that the initial disease progression usually goes unnoticed, with symptoms only becoming apparent in the more advanced stages when irreversible damage has occurred. Diet quality has a significant impact on brain health and hence can also influence ND development. For example, the Mediterranean diet (MedDiet) has demonstrated many valuable attributes that can reduce ND incidences and improve cognitive function. This review looked at dietary components, natural compounds and medicinal plants that have shown to be beneficial for brain health in ND. The authors discussed the MedDiet followed by a brief review of dietary supplements, including N-acetylcysteine (NAC), phospholipids (Phosphatidylserine, Phosphatidylcholine), Gamma-aminobutyric acid, melatonin, omega-3 fatty acids, neurotropic vitamin B (B1, B6 and B12), S-adenosyl methionine (SAMe), the amino acid tryptophan, magnesium and various polyphenols. Several medicinal plants are reviewed that have demonstrated positive effects on preventing or alleviating neurological diseases. This includes Withania somnifera (Ashwagandha), Baccopa monnieri (Brahmi), Acorus calamus (Calamus) and Hypericum perforatum (St. Johns Wort). The review concluded that many bioactive compounds and plant constituents that can be obtained from a qualitative diet, as well as certain medicinal plants and supplements, can help preserve and promote brain health and prevent the onset of ND. Large clinical trials are needed to assess their suitability for their wider use.
Abstract
A healthy diet shapes a healthy mind. Diet quality has a strong association with brain health. Diet influences the onset and consequences of neurological diseases, and dietary factors may influence mental health at individual and population level. The link between unhealthy diet, impaired cognitive function and neurodegenerative diseases indicates that adopting a healthy diet would ultimately afford prevention and management of neurological diseases and brain aging. Neurodegenerative diseases are of multifactorial origin and result in progressive loss of neuronal function in the brain, leading to cognitive impairment and motoneuron disorders. The so-called Mediterranean diet (MedDiet) with its healthy ingredients rich in antioxidant, anti-inflammatory, immune, neuroprotective, antidepressant, antistress and senolytic activity plays an essential role in the prevention and management of neurological diseases and inhibits cognitive decline in neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's diseases. The MedDiet also modulates the gut-brain axis by promoting a diversity of gut microbiota. In view of the importance of diet in neurological diseases management, this review focuses on the dietary components, natural compounds and medicinal plants that have proven beneficial in neurological diseases and for brain health. Among them, polyphenols, omega-3 fatty acids, B vitamins and several ayurvedic herbs have promising beneficial effects.
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Energy Drinks and Sleep among Adolescents.
Tomanic, M, Paunovic, K, Lackovic, M, Djurdjevic, K, Nestorovic, M, Jakovljevic, A, Markovic, M
Nutrients. 2022;14(18)
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Sleep deprivation is a common problem among adolescents. There has been an increase in the consumption of energy drinks among adolescents in recent years. It is well known that energy drinks contain caffeine, sugar, and amino acids such as taurine, B vitamins, Ginseng, and guarana, which have psychoactive properties and disrupt the circadian rhythm. Insufficient sleep can affect genes involved in circadian rhythm and serotonin pathways, resulting in a higher risk of developing mental health problems. Therefore, researchers accessed the data from a population-based cross-sectional study to evaluate the effect of an energy drink on sufficient sleep in male and female adolescents. This study found that high energy drink consumption negatively affected sufficient sleep in male and female adolescents, with boys consuming energy drinks more frequently. The intake of vegetables and water, as well as regular physical activity, were positively correlated with adequate sleep in male adolescents. Physical activity and sufficient sleep were positively correlated in girls. Girls who used sedatives were less likely to get sufficient sleep. In order to determine how the different ingredients of energy drinks affect the sleep quality and neurodevelopment of adolescents individually and synergistically, further robust studies are required. The results of this study may help healthcare professionals to understand the adverse effects of energy drinks on adolescents.
Abstract
Many adolescents worldwide have the problem of meeting recommended nightly sleep hours. The causes of sleep disturbance are multifactorial, but interest in food's effect on sleep has dramatically increased lately. In this study, we investigated the association between regular energy drink (ED) intake (weekly or more frequent) and sufficient sleep (SS) (≥8 h) in adolescents. Additional objectives were to examine the relationship between health-related behaviors and SS, stratified by gender. A population-based cross-sectional study was conducted during the 2019/2020 school year from 12 schools in Belgrade. There were 1287 students aged 15 to 19 who participated (37.4% male). We used a modified version of the food frequency questionnaire adapted for Serbian adolescents. Logistic regression revealed that regular ED consumption was an independent risk factor negatively related to SS in both sexes. Additionally, daily vegetable and water intake (≥2 L) showed a positive correlation with SS in boys, while in girls, the odds of realizing SS decreased with statements of sedative use. In conclusion, we show that ED intake is negatively associated with SS in both sexes; daily vegetable and water intake (≥2 L) may raise the odds of SS in boys, while sedative use may decrease the chances of SS in girls.
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The effect of Melatonin on Improving the benign Prostatic Hyperplasia Urinary Symptoms, a Randomized Clinical Trial.
Fotovat, A, Samadzadeh, B, Ayati, M, Nowroozi, MR, Momeni, SA, Yavari, S, Nasseri, A, Sharifi, L
Urology journal. 2022;19(5):406-411
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Benign prostatic hyperplasia (BPH) is a common issue in men older than 40. BPH is accompanied by irritating and obstructive symptoms that sometimes lead to surgery due to lack of recovery. Tamsulosin is an alpha-receptor blocker that is considered a standard treatment for patients. The aim of this study was to investigate the effect of melatonin [a hormone secreted by the pineal gland at night that regulates the sleep-wake cycle] along with standard treatment on improving the BPH urinary symptoms as well as patients’ quality of life due to their urinary problems. This study is a single centre, parallel group randomised, double-blind clinical trial with balanced randomisation. Patients (n = 108) were randomly allocated to one of the two groups. Results show the combination of melatonin and tamsulosin was significantly effective in treating the symptoms of frequency and nocturia in patients with BPH. Authors conclude that their findings can be used to pave the way to improving the symptoms of patients with BPH.
Abstract
PURPOSE to investigate the effect of melatonin along with tamsulosin in improving BPH urinary symptoms. MATERIALS AND METHODS A total of 108 men with BPH symptoms, age of ≥ 50 years, and International Prostate Symptom Score (IPSS) ≥ 8 entered into the parallel group randomized, double-blind clinical trial with balanced randomization. The treatment group received of 3mg melatonin plus 0.4mg tamsulosin and the control group received placebo plus 0.4mg tamsulosin. Patients and physicians were concealed by sealed and opaque envelopes. Symptoms were assessed at baseline and 1 month after treatment. Finally all scores at the initial and end of the study were compared and analyzed using SPSS software. RESULTS This study showed that adding melatonin to the classic treatment of BPH patients with tamsulosin could significantly reduce the likelihood of nocturia by 2.39 times (95% CI: 1.07-5.32, OR = 2.39, p = 0.033) and could also reduce the frequency of urination by 2.59 times (95% CI: 1.15-5.84, OR = 2.59, p = 0.021). There was no statistically significant difference between the two groups in IPSS, intermittency, incomplete emptying, straining, urgency, and weak stream. CONCLUSION Melatonin plus tamsulosin treatment is associated with a significant improvement of nocturia and frequency in patients with benign proststic hyperplasia. However, it is necessary to do more studies.
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Evidence for the Benefits of Melatonin in Cardiovascular Disease.
Tobeiha, M, Jafari, A, Fadaei, S, Mirazimi, SMA, Dashti, F, Amiri, A, Khan, H, Asemi, Z, Reiter, RJ, Hamblin, MR, et al
Frontiers in cardiovascular medicine. 2022;9:888319
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Cardiovascular disease (CVD) encompasses a group of disorders involving blood vessels or the heart. The beneficial effects of melatonin [hormone] in treating various human diseases have been broadly investigated. Melatonin is an indoleamine-derived molecule, which is synthesised at night. The aim of this review was to point out therapeutic potentials of melatonin in the treatment of CVDs with an emphasis on the molecular mechanisms of action. This review shows that: - nearly all the studies have reported positive effects of melatonin on cardiovascular physiology, and the prevention of damage to the myocardium after heart attack, reperfusion injury, or sepsis. - melatonin can help blood pressure and heart arrhythmia. - some clinical trials indicated that the utilization of melatonin in CVDs is associated with more inconsistencies regarding its cardioprotective effects. Authors conclude that further preclinical and clinical studies are required to better delineate the cardiovascular benefits of melatonin.
Abstract
The pineal gland is a neuroendocrine gland which produces melatonin, a neuroendocrine hormone with critical physiological roles in the circadian rhythm and sleep-wake cycle. Melatonin has been shown to possess anti-oxidant activity and neuroprotective properties. Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.
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Essential Hypertension and Oxidative Stress: Novel Future Perspectives.
Franco, C, Sciatti, E, Favero, G, Bonomini, F, Vizzardi, E, Rezzani, R
International journal of molecular sciences. 2022;23(22)
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High blood pressure is one of the main risk factors for cardiovascular disease and a significant contributor to the development of strokes, heart attacks, and heart and kidney failure leading to early disability and reduced life expectancy. Essential or primary hypotension makes up 95% of high blood pressure cases, which is abnormally elevated blood pressure that is not a result of any other medical condition. Essential hypertension arises from various factors such as diet, lifestyle, environmental and genetic influences. Despite many available medications, not all patients attain well-managed blood pressure levels. Unmanaged high blood pressure can, over time, lead to narrowing and stiffening of the blood vessels and ultimately to structural and functional changes in the blood tissues. In part, this is mediated by oxidative stress, changes in antioxidant capacity and chronic low-grade inflammation, which damage the blood vessels' endothelial tissue and result in vascular stiffness. Melatonin is one of the most potent antioxidants found in nature and has been studied in short-term trials for its blood pressure lowering, antioxidant and vascular protective effects. This small open-label randomised study sought to get a better understanding of the long-term use of melatonin. Initially, the study assessed endothelial tissue damage, oxidative status and vascular stiffness in patients with high blood pressure. Subsequently, some of the participants received a low-dose melatonin supplement (1 mg/day) for one year, whilst being monitored for clinical and structural vascular changes. The study included 23 patients and 14 in the final analysis. After one year, the results showed a significant improvement in arterial stiffness in the melatonin group (11) and an improvement in endothelial tissue function, though the latter was not at statistically significant levels. Improvement in arterial stiffness seemed to be linked to a reduction in total antioxidant capacity (TAC). These findings suggest that melatonin can contribute to restoring oxidative balance in blood plasma, which reflects improved arterial stiffness. The study also demonstrated that besides being a well-tolerated intervention, melatonin also has clinical benefits even when administered at lower doses than normal.
Abstract
Among cardiovascular diseases, hypertension is one of the main risk factors predisposing to fatal complications. Oxidative stress and chronic inflammation have been identified as potentially responsible for the development of endothelial damage and vascular stiffness, two of the primum movens of hypertension and cardiovascular diseases. Based on these data, we conducted an open-label randomized study, first, to evaluate the endothelial damage and vascular stiffness in hypertense patients; second, to test the effect of supplementation with a physiological antioxidant (melatonin 1 mg/day for 1 year) in patients with essential hypertension vs. hypertensive controls. Twenty-three patients of either gender were enrolled and randomized 1:1 in two groups (control and supplemented group). The plasmatic total antioxidant capacity (as a marker of oxidative stress), blood pressure, arterial stiffness, and peripheral endothelial function were evaluated at the beginning of the study and after 1 year in both groups. Our results showed that arterial stiffness improved significantly (p = 0.022) in supplemented patients. The endothelial function increased too, even if not significantly (p = 0.688), after 1 year of melatonin administration. Moreover, the supplemented group showed a significative reduction in TAC levels (p = 0.041) correlated with the improvement of arterial stiffness. These data suggest that melatonin may play an important role in reducing the serum levels of TAC and, consequently, in improving arterial stiffness.
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The Window Matters: A Systematic Review of Time Restricted Eating Strategies in Relation to Cortisol and Melatonin Secretion.
Chawla, S, Beretoulis, S, Deere, A, Radenkovic, D
Nutrients. 2021;13(8)
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Time-Restricted Eating (TRE) is an eating pattern based on the circadian rhythm that gives the body a daily fasting period. This involves limiting daily food intake to 8–12 hours with an intention to prolong the time spent in a fasting state. In fact, chrono-nutrition is an emerging field of nutritional science that aims to understand how timing of food-intake may impact our health by affecting our circadian rhythm. The aim of this study was to examine the effects of two patterns of TRE, traditional TRE (a predetermined window of eating and fasting) and Ramadan fasting, on two markers of circadian rhythm, cortisol and melatonin. This study was a systematic review and meta-analysis of fourteen studies (13 reported results on cortisol, and four on melatonin). Results showed that: - Ramadan practice of TRE resulted in a reduced waking response of cortisol, and in most cases a statistically significant increase relative to non-Ramadan in the evening. - the Ramadan studies also found significant reductions in levels of nocturnal melatonin during Ramadan compared to baseline. - in the non-Ramadan TRE studies, skipping dinner led to a decreased evening cortisol level, and, potentially, an elevated morning level (however not in all cases waking time was accounted for). - skipping breakfast led to a relative increase in midday cortisol. Authors conclude that their findings indicated a potential blunting of the circadian cortisol rhythm during Ramadan and a reduction in melatonin which could lead to poor sleep duration and quality.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Other human and animal studies have highlighted the benefits of restricting the feeding window for longevity and metabolic health.
- Whether one chooses early or late TRE may help to determine the optimal time of alertness and sleep.
- Early TRE, which involves skipping dinner, may allow for greater alertness in the morning as the lower levels of cortisol at night can improve sleep quality and higher morning cortisol raises alertness, optimising wakefulness and productivity.
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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X
B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction:
This systematic review aimed to examine the effects of two patterns of Time Restricted Feeding (TRE): (1) traditional TRE, and (2) Ramadan fasting, on two markers of circadian rhythm: (1) cortisol and (2) melatonin.
Methods
- A search was performed on PubMed, and Web of Science (all databases) up to December 2020 using search terms relating to “time-restricted eating”, “intermittent fasting”, “cortisol”, “melatonin”, and “orexin”.
- 14 randomised controlled trials and observational studies that met the criteria were included.
- Quality assessment of all studies was performed
Results
14 studies met the inclusion criteria. 10 of the studies used TRE in the context of Ramadan (total n=242) whilst 4 followed non-Ramadan TRE protocols (total n=124). Of the 14 studies identified in the literature review, 13 reported results on cortisol, and 4 on melatonin.
- All 4 melatonin studies found a statistically significant reduction of melatonin (p < 0.05) during Ramadan.
- 2 of 3 studies assessing 24-h serum cortisol changes during Ramadan noted an “abolishing” of the circadian rhythm of cortisol (p < 0.05), meaning there was a flattening of cortisol levels during the fasting month compared with the non-fasting month.
- All 13 cortisol studies recorded a cortisol shift in response to time restricted eating, albeit over different time frames and different cortisol recording methods.
- 1 randomised 4-day crossover study (n=11) found skipping dinner resulted in significantly reduced evening cortisol (p=0.03) and non-significantly raised morning cortisol. Skipping breakfast resulted in significantly reduced morning cortisol (p=0.10) .
- 1 observational study of females aged 18-45 (n-65) found that skipping breakfast demonstrated decreased morning (waking) cortisol, elevated midday cortisol, and no significant evening cortisol differences compared to the control group.
Conclusion
The potential blunting of the circadian cortisol rhythm during Ramadan may impact the HPA axis and is associated with poor cardio-metabolic outcomes. A reduction in melatonin could lead to poor sleep duration and quality.
Clinical practice applications:
- The mechanisms behind these findings are not well understood, but are likely to include: the complex endocrine interplay with insulin response and glucocorticoid secretion.
- Caution must be taken in terms of generalisability due to the small sample size of the included studies
Early or late TRE can determine the optimal time of alertness and sleep:
- Early TRE (eating 8am-2pm / skipping dinner), may allow for greater alertness in the morning as the lower levels of cortisol at night can improve sleep quality and higher morning cortisol raises alertness, optimising wakefulness and productivity.
- Late TRE (skipping breakfast) may provide greater alertness mid-day, due to an intensified cortisol response mid-day.
Considerations for future research:
In order to better understand the effects of meal timing on health outcomes, further larger studies should be conducted. They should:
- Examine TRE during the inactive and active phases of the circadian rhythm under controlled conditions.
- Exclude studies relating to pregnancy, pathology, and athletic status.
- Ensure sufficient control for confounding factors that can affect serum parameters, including sleep duration and timing, total energy expenditure, and light exposure
Abstract
Time-Restricted Eating is an eating pattern based on the circadian rhythm which limits daily food intake (usually to ≤12 h/day), unique in that no overt restriction is imposed on the quality, nor quantity, of food intake. This paper aimed to examine the effects of two patterns of TRE, traditional TRE, and Ramadan fasting, on two markers of circadian rhythm, cortisol and melatonin. PubMed and Web of Science were searched up to December 2020 for studies examining the effects of time restricted eating on cortisol and melatonin. Fourteen studies met our inclusion criteria. All Ramadan papers found statistically significant decrease in melatonin (p < 0.05) during Ramadan. Two out of the three Ramadan papers noted an abolishing of the circadian rhythm of cortisol (p < 0.05). The non-Ramadan TRE papers did not examine melatonin, and cortisol changes were mixed. In studies comparing TRE to control diets, Stratton et al. found increased cortisol levels in the non-TRE fasting group (p = 0.0018) and McAllister et al. noted no difference. Dinner-skipping resulted in significantly reduced evening cortisol and non-significantly raised morning cortisol. Conversely, breakfast skipping resulted in significantly reduced morning cortisol. This blunting indicates a dysfunctional HPA axis, and may be associated with poor cardio-metabolic outcomes. There is a paucity of research examining the effects of TRE on cortisol and melatonin. The contrasting effect of dinner and breakfast-skipping should be further examined to ascertain whether timing the feeding window indeed has an impact on circadian rhythmicity.