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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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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.
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Effects of Acute Resistance Exercise with and without Whole-Body Electromyostimulation and Endurance Exercise on the Postprandial Glucose Regulation in Patients with Type 2 Diabetes Mellitus: A Randomized Crossover Study.
Holzer, R, Schulte-Körne, B, Seidler, J, Predel, HG, Brinkmann, C
Nutrients. 2021;13(12)
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Over 460 million people worldwide suffer from Type 2 Diabetes. Previous studies have found that endurance training combined with resistance training increases insulin sensitivity and glucose tolerance. Due to its ability to enhance physical performance and to save time during exercise sessions, electromyostimulation is becoming increasingly popular in health and recreational sports. Using a randomised crossover design, the study measures the effects of different exercise strategies and intensities on glucose regulation post-prandially. To assess the effect of post-prandial glucose regulation on Type 2 Diabetic patients, six patients performed 20 minutes of resistance exercise with whole-body electromyostimulation, conventional exercise without whole-body electromyostimulation, and endurance exercise. All types of exercise were effective at lowering blood glucose levels, even at a short duration of 20 minutes. Electrical stimulation did not affect the effect of exercise in any significant way. It is therefore necessary to conduct further robust long-term studies on the effects of electromyostimulation and resistance or endurance training on lowering postprandial blood glucose levels. The results of this study can be used by healthcare professionals to better understand the relationship between exercise and glucose regulation, which may be useful when making clinical decisions for people with Type 2 Diabetes or obesity.
Abstract
BACKGROUND Long hyperglycemic episodes trigger complications in type 2 diabetes mellitus (T2DM) patients. Postprandial glucose excursions can be reduced by acute physical activity. However, it is not yet clear which type of exercise has the best effect on postprandial glucose levels. METHODS Six T2DM patients participated in three 20-min moderate-intensity exercise sessions after breakfast in a randomized order: resistance exercise with whole-body electromyostimulation (WB-EMS), resistance exercise without electromyostimulation (RES) and cycling endurance exercise (END). A continuous glucose monitoring system recorded glucose dynamics. RESULTS Postprandially-increased glucose levels decreased in all cases. Time to baseline (initial value prior to meal intake) was quite similar for WB-EMS, RES and END. Neither glucose area under the curve (AUC), nor time in range from the start of the experiment to its end (8 h later) differed significantly. A Friedman analysis of variance, however, revealed an overall significant difference for AUC in the post-exercise recovery phase (END seems to have superior effects, but post-hoc tests failed statistical significance). CONCLUSIONS There are no notable differences between the effects of the different types of exercise on glucose levels, especially when comparing values over a longer period of time.
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Stress matters: Randomized controlled trial on the effect of probiotics on neurocognition.
Papalini, S, Michels, F, Kohn, N, Wegman, J, van Hemert, S, Roelofs, K, Arias-Vasquez, A, Aarts, E
Neurobiology of stress. 2019;10:100141
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Increasing animal studies indicate the role of probiotics in regulating mood and cognition through the gut-brain axis, however in human studies evidence of this causal association is lacking. The aim of this double-blind, randomised, placebo-controlled intervention was to investigate the effects of probiotics on neurocognitive measures in 58 healthy participants. Participants were randomly assigned to either probiotic or placebo group and were tested once before and after the 28-day intervention. The neurocognitive outcomes measured included emotion reactivity, emotion regulation, cognitive control and the effects of acute stress on working memory. These were assessed through functional MRI (fMRI) and questionnaires. This study found when stress was induced, probiotic supplementation led to a significant improvement in working memory performance. Without stress, there was no causal association between neurocognitive outcomes and probiotic intake. Based on these results, the authors conclude that during challenging situations, probiotics can aid in buffering the detrimental effects of stress on cognition.
Abstract
Probiotics are microorganisms that provide health benefits when consumed. In animals, probiotics reverse gut microbiome-related alterations in depression-like symptoms, in cognition, and in hormonal stress response. However, in humans, a causal understanding of the gut-brain link in emotion and cognition is lacking. Additionally, whether the effects of probiotics on neurocognition are visible only in presence of stress, remains unclear. We investigated the effects of a multispecies probiotic (Ecologic®Barrier) on specific neurocognitive measures of emotion reactivity, emotion regulation, and cognitive control using fMRI. Critically, we also tested whether probiotics can buffer against the detrimental effects of acute stress on working memory. In a double blind, randomized, placebo-controlled, between-subjects intervention study, 58 healthy participants were tested once before and once after a 28-day intervention. Without stress induction, probiotics did not affect brain, behavioral, or related self-report measures. However, relative to placebo, the probiotics group did show a significant stress-related increase in working memory performance after supplementation. This change was associated with intervention-related neural changes in frontal cortex during cognitive control exclusively in the probiotics group. Overall, our results show neurocognitive effects of a multispecies probiotic in healthy women only under challenging situations, buffering against the detrimental effects of stress on cognition.
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Zinc, Magnesium, Selenium and Depression: A Review of the Evidence, Potential Mechanisms and Implications.
Wang, J, Um, P, Dickerman, BA, Liu, J
Nutrients. 2018;10(5)
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Adequate micronutrient consumption and mental health are of major public health importance. Recent findings suggest micronutrient deficiencies may play a role in the development and progression of depression, yet the findings remain unclear. The aim of this review is to present the recent evidence on the association between several micronutrients and depression and discuss the potential mechanisms and clinical implications. Based on the current literature, evidence shows an association between both zinc and magnesium deficiency and the risk of depression, with stronger evidence supporting zinc. Studies on selenium are limited or inconclusive. According to these findings, the authors support the importance of adequate micronutrient consumption for promoting mental health. They suggest future research should investigate the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression to better inform current prevention and treatment strategies.
Abstract
Micronutrient deficiency and depression are major global health problems. Here, we first review recent empirical evidence of the association between several micronutrients—zinc, magnesium, selenium—and depression. We then present potential mechanisms of action and discuss the clinical implications for each micronutrient. Collectively, empirical evidence most strongly supports a positive association between zinc deficiency and the risk of depression and an inverse association between zinc supplementation and depressive symptoms. Less evidence is available regarding the relationship between magnesium and selenium deficiency and depression, and studies have been inconclusive. Potential mechanisms of action involve the HPA axis, glutamate homeostasis and inflammatory pathways. Findings support the importance of adequate consumption of micronutrients in the promotion of mental health, and the most common dietary sources for zinc and other micronutrients are provided. Future research is needed to prospectively investigate the association between micronutrient levels and depression as well as the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression.
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Impact of Experimentally Induced Cognitive Dietary Restraint on Eating Behavior Traits, Appetite Sensations, and Markers of Stress during Energy Restriction in Overweight/Obese Women.
Morin, I, Bégin, C, Maltais-Giguère, J, Bédard, A, Tchernof, A, Lemieux, S
Journal of obesity. 2018;2018:4259389
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The treatment of obesity has become a public health priority given the negative impact of this condition on physical and mental health. The aim of this study was to compare the effects of energy restriction alone or in combination with induced cognitive dietary restraint (CDR) on eating behaviour traits, appetite sensations, and markers of stress in overweight and obese premenopausal women. The study is a single-blinded randomised clinical study which recruited premenopausal women aged between 26 and 50 years. The participants were randomised to either an energy-restriction-plus-induced CDR condition (CDR+group) or an energy-restriction-without induced CDR condition (CDR−group). Results indicate that inducing CDR in a context of energy restriction had no further effects on eating behaviour traits, appetite sensations, and markers of stress in the short term as well as in the longer term than energy restriction alone. Authors conclude that increasing CDR has no negative impact on factors regulating energy balance in the context of energy restriction.
Abstract
Weight loss has been associated with changes in eating behaviors and appetite sensations that favor a regain in body weight. Since traditional weight loss approaches emphasize the importance of increasing cognitive dietary restraint (CDR) to achieve negative energy imbalance, it is difficult to untangle the respective contributions of energy restriction and increases in CDR on factors that can eventually lead to body weight regain. The present study aimed at comparing the effects of energy restriction alone or in combination with experimentally induced CDR on eating behavior traits, appetite sensations, and markers of stress in overweight and obese women. We hypothesized that the combination of energy restriction and induced CDR would lead to more prevalent food cravings, increased appetite sensations, and higher cortisol concentrations than when energy restriction is not coupled with induced CDR. A total of 60 premenopausal women (mean BMI: 32.0 kg/m2; mean age: 39.4 y) were provided with a low energy density diet corresponding to 85% of their energy needs during a 4-week fully controlled period. At the same time, women were randomized to either a condition inducing an increase in CDR (CDR+ group) or a condition in which CDR was not induced (CRD- group). Eating behavior traits (Three-Factor Eating Questionnaire and Food Craving Questionnaire), appetite sensations (after standardized breakfast), and markers of stress (Perceived Stress Scale; postawakening salivary cortisol) were measured before (T = 0 week) and after (T = 4 weeks) the 4-week energy restriction, as well as 3 months later. There was an increase in CDR in the CDR+ group while no such change was observed in the CDR- group (p=0.0037). No between-group differences were observed for disinhibition, hunger, cravings, appetite sensations, perceived stress, and cortisol concentrations. These results suggest that a slight increase in CDR has no negative impact on factors regulating energy balance in the context of energy restriction.
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Association between weight bias internalization and metabolic syndrome among treatment-seeking individuals with obesity.
Pearl, RL, Wadden, TA, Hopkins, CM, Shaw, JA, Hayes, MR, Bakizada, ZM, Alfaris, N, Chao, AM, Pinkasavage, E, Berkowitz, RI, et al
Obesity (Silver Spring, Md.). 2017;25(2):317-322
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Weight stigma is a psychosocial consequence in which individuals with obesity experience public discrimination and devaluation. Some individuals apply these negative stereotypes to themselves, which creates a self-directed stigma referred to as weight bias internalization (WBI). While studies have found perceived weight discrimination to be associated with an increased risk of mortality, no study has investigated the relationship between WBI and obesity on the risk of developing metabolic syndrome (MetS). The aim of this study is to examine the relationship between WBI and MetS. The authors hypothesised that among obese individuals, higher levels of WBI would be associated with increased odds of having MetS. Among the 178 obese adults recruited, 159 completed the study. Tests included anthropometric measurements, blood analysis, the Weight Bias Internalization Scale (WBIS) and the Patient Health Questionnaire. This study found that individuals who self-stigmatise may have a heightened risk of dyslipidemia, one component of MetS. Based on these results, the authors conclude that weight stigma is a chronic stressor and may contribute to poor health. Future studies are needed to identify specific pathways in which WBI exacerbates cardiometaoblic risk factors.
Abstract
OBJECTIVE Weight stigma is a chronic stressor that may increase cardiometabolic risk. Some individuals with obesity self-stigmatize (i.e., weight bias internalization, WBI). No study to date has examined whether WBI is associated with metabolic syndrome. METHODS Blood pressure, waist circumference, and fasting glucose, triglycerides, and high-density lipoprotein cholesterol were measured at baseline in 178 adults with obesity enrolled in a weight-loss trial. Medication use for hypertension, dyslipidemia, and prediabetes was included in criteria for metabolic syndrome. One hundred fifty-nine participants (88.1% female, 67.3% black, mean BMI = 41.1 kg/m2 ) completed the Weight Bias Internalization Scale and Patient Health Questionnaire (PHQ-9, to assess depressive symptoms). Odds ratios and partial correlations were calculated adjusting for demographics, BMI, and PHQ-9 scores. RESULTS Fifty-one participants (32.1%) met criteria for metabolic syndrome. Odds of meeting criteria for metabolic syndrome were greater among participants with higher WBI, but not when controlling for all covariates (OR = 1.46, 95% CI = 1.00-2.13, P = 0.052). Higher WBI predicted greater odds of having high triglycerides (OR = 1.88, 95% CI = 1.14-3.09, P = 0.043). Analyzed categorically, high (vs. low) WBI predicted greater odds of metabolic syndrome and high triglycerides (Ps < 0.05). CONCLUSIONS Individuals with obesity who self-stigmatize may have heightened cardiometabolic risk. Biological and behavioral pathways linking WBI and metabolic syndrome require further exploration.
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The Effect of Post-Resistance Exercise Amino Acids on Plasma MCP-1 and CCR2 Expression.
Wells, AJ, Hoffman, JR, Jajtner, AR, Varanoske, AN, Church, DD, Gonzalez, AM, Townsend, JR, Boone, CH, Baker, KM, Beyer, KS, et al
Nutrients. 2016;8(7)
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Background: Innate immune response is generally considered to have an important role in tissue remodeling of the damaged localised skeletal muscle as a result of intense resistance exercise. Monocytes are leukocytes that also influence our adaptive immune system. Aim & Objective: The purpose of this study was to examine the changes in the markers of monocytes recruitment after a bout of high resistance exercise and ingestion of amino acid supplement. Method: Ten resistant trained men between the ages of 18 and 35 were recruited in this randomised crossover design study. Blood sample were taken at various time to measure and assess the plasma concentrations of monocyte chemoattractant protein 1 (MCP-1), myoglobin, cortisol and insulin concentrations; and expressions of C-C chemokine receptor-2 (CCR2), and macrophage-1 antigen (CD11b) on classical monocytes. Result & conclusion: No significant differences were noted for the markers myoglobin, insulin or cortisol in the treatment group in this study. Ingestion of supplement increased the CCR2 expression on CD14+ monocytes at 1H, 2H and 5H(P’s ≤ 0.001) after the exercise, but did not appear to have any influence on CD11b expression on CD14++CD16- ́ monocytes. To conclude it seems that amino acids are important regulator of immune response but more research is needed.
Abstract
The recruitment and infiltration of classical monocytes into damaged muscle is critical for optimal tissue remodeling. This study examined the effects of an amino acid supplement on classical monocyte recruitment following an acute bout of lower body resistance exercise. Ten resistance-trained men (24.7 ± 3.4 years; 90.1 ± 11.3 kg; 176.0 ± 4.9 cm) ingested supplement (SUPP) or placebo (PL) immediately post-exercise in a randomized, cross-over design. Blood samples were obtained at baseline (BL), immediately (IP), 30-min (30P), 1-h (1H), 2-h (2H), and 5-h (5H) post-exercise to assess plasma concentrations of monocyte chemoattractant protein 1 (MCP-1), myoglobin, cortisol and insulin concentrations; and expressions of C-C chemokine receptor-2 (CCR2), and macrophage-1 antigen (CD11b) on classical monocytes. Magnitude-based inferences were used to provide inferences on the true effects of SUPP compared to PL. Changes in myoglobin, cortisol, and insulin concentrations were similar between treatments. Compared to PL, plasma MCP-1 was "very likely greater" (98.1% likelihood effect) in SUPP at 2H. CCR2 expression was "likely greater" at IP (84.9% likelihood effect), "likely greater" at 1H (87.7% likelihood effect), "very likely greater" at 2H (97.0% likelihood effect), and "likely greater" at 5H (90.1% likelihood effect) in SUPP, compared to PL. Ingestion of SUPP did not influence CD11b expression. Ingestion of an amino acid supplement immediately post-exercise appears to help maintain plasma MCP-1 concentrations and augment CCR2 expression in resistance trained men.
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Excessive Sugar Consumption May Be a Difficult Habit to Break: A View From the Brain and Body.
Tryon, MS, Stanhope, KL, Epel, ES, Mason, AE, Brown, R, Medici, V, Havel, PJ, Laugero, KD
The Journal of clinical endocrinology and metabolism. 2015;100(6):2239-47
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It is widely known that people eat to relieve stress. Rodent studies have shown that sugar consumption switches off activity in the networks that mediate the stress induced hypothalamic-pituitary-adrenal (HPA) autonomic nervous system. This study aimed to compare the effects of consuming drinks, sweetened with either sucrose or aspartame, on cortisol responses induced by stress. The researchers found that sucrose consumption was associated reduced stress induced cortisol, and a trend towards lower cortisol. Aspartame did not have the same effect. The Montreal Imaging Stress Task (MIST) was used to map areas of the brain associated with stress. It was found that sugar consumption caused a diminished response to MIST after two weeks of sucrose consumption, and cortisol was elevated after two weeks of aspartame. The study concluded that brain negative feedback pathways are affected by sugar, and consequently may make stressed individuals more reliant or addicted to sugar. In turn, this increases the likelihood of obesity and its associated chronic diseases.
Abstract
CONTEXT Sugar overconsumption and chronic stress are growing health concerns because they both may increase the risk for obesity and its related diseases. Rodent studies suggest that sugar consumption may activate a glucocorticoid-metabolic-brain-negative feedback pathway, which may turn off the stress response and thereby reinforce habitual sugar overconsumption. OBJECTIVE The objective of the study was to test our hypothesized glucocorticoid-metabolic-brain model in women consuming beverages sweetened with either aspartame of sucrose. DESIGN This was a parallel-arm, double-masked diet intervention study. SETTING The study was conducted at the University of California, Davis, Clinical and Translational Science Center's Clinical Research Center and the University of California, Davis, Medical Center Imaging Research Center. PARTICIPANTS Nineteen women (age range 18-40 y) with a body mass index (range 20-34 kg/m(2)) who were a subgroup from a National Institutes of Health-funded investigation of 188 participants assigned to eight experimental groups. INTERVENTION The intervention consisted of sucrose- or aspartame-sweetened beverage consumption three times per day for 2 weeks. MAIN OUTCOME MEASURES Salivary cortisol and regional brain responses to the Montreal Imaging Stress Task were measured. RESULTS Compared with aspartame, sucrose consumption was associated with significantly higher activity in the left hippocampus (P = .001). Sucrose, but not aspartame, consumption associated with reduced (P = .024) stress-induced cortisol. The sucrose group also had a lower reactivity to naltrexone, significantly (P = .041) lower nausea, and a trend (P = .080) toward lower cortisol. CONCLUSION These experimental findings support a metabolic-brain-negative feedback pathway that is affected by sugar and may make some people under stress more hooked on sugar and possibly more vulnerable to obesity and its related conditions.
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Influence of a montmorency cherry juice blend on indices of exercise-induced stress and upper respiratory tract symptoms following marathon running--a pilot investigation.
Dimitriou, L, Hill, JA, Jehnali, A, Dunbar, J, Brouner, J, McHugh, MP, Howatson, G
Journal of the International Society of Sports Nutrition. 2015;12:22
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Prolonged exercise, such as marathon running, is associated with upper respiratory tract (URT) symptoms and airway inflammation. Tart Montmorency cherry juice, high in phytochemicals such as anthocyanins and quercetin, has been shown to have anti-inflammatory and anti-oxidative properties and therefore may help reduce inflammation and oxidative stress triggered by exercise. In this pilot study, twenty marathon runners were randomly assigned to receive two servings a day of either a placebo drink or cherry juice for eight days ─ prior, during and after a marathon run. Any URT symptoms were reported, and inflammatory markers were measured pre- and post-race and 24 and 48 hrs after the race, from saliva (immunoglobulins and cortisol) and serum (C-reactive protein, CRP). No differences in the effect on immunoglobulins and cortisol were found between the two groups. The increase in CRP was significantly lower in the cherry juice group compared to the placebo group. 50% of the runners in the placebo group developed URT symptoms, while none were reported in the cherry juice group. The authors conclude that Montmorency cherry juice may protect the URT from inflammatory symptoms triggered by exercise. They propose further studies with larger sample size of participants, suffering from various inflammatory respiratory conditions.
Abstract
BACKGROUND Prolonged exercise, such as marathon running, has been associated with an increase in respiratory mucosal inflammation. The aim of this pilot study was to examine the effects of Montmorency cherry juice on markers of stress, immunity and inflammation following a Marathon. METHODS Twenty recreational Marathon runners consumed either cherry juice (CJ) or placebo (PL) before and after a Marathon race. Markers of mucosal immunity secretory immunoglobulin A (sIgA), immunoglobulin G (IgG), salivary cortisol, inflammation (CRP) and self-reported incidence and severity of upper respiratory tract symptoms (URTS) were measured before and following the race. RESULTS All variables except secretory IgA and IgG concentrations in saliva showed a significant time effect (P <0.01). Serum CRP showed a significant interaction and treatment effect (P < 0.01). The CRP increase at 24 and 48 h post-Marathon was lower (P < 0.01) in the CJ group compared to PL group. Mucosal immunity and salivary cortisol showed no interaction effect or treatment effect. The incidence and severity of URTS was significantly greater than baseline at 24 h and 48 h following the race in the PL group and was also greater than the CJ group (P < 0.05). No URTS were reported in the CJ group whereas 50 % of runners in the PL group reported URTS at 24 h and 48 h post-Marathon. CONCLUSIONS This is the first study that provides encouraging evidence of the potential role of Montmorency cherries in reducing the development of URTS post-Marathon possibly caused by exercise-induced hyperventilation trauma, and/or other infectious and non-infectious factors.
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Modifying influence of dietary sugar in the relationship between cortisol and visceral adipose tissue in minority youth.
Gyllenhammer, LE, Weigensberg, MJ, Spruijt-Metz, D, Allayee, H, Goran, MI, Davis, JN
Obesity (Silver Spring, Md.). 2014;22(2):474-81
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Visceral adipose tissue (VAT) is one of the strongest risk factors associated with obesity and related co-morbidities. A potential mechanism for this association involves cortisol and cortisol receptors, however the specific interaction of cortisol and diet upon fat deposition has not yet been explored in humans. The purpose of this cross-sectional study was to assess the impact of a high-fat, high-sugar diet on the association between stress and visceral fat in 165 overweight minority youth. The results of this study showed that cortisol was significantly associated with elevated VAT under conditions of high sugar intake in this population. Based on these findings, the authors conclude that dietary sugar may play a crucial role in moderating the adverse effects of cortisol.
Abstract
OBJECTIVE Cortisol has been associated with preferential visceral adipose tissue (VAT) deposition; however, findings in humans are mixed, which may be clarified when diet is considered. DESIGN AND METHODS Participants included 165 African-American and Latino, overweight adolescents (BMI% 97.2±3.2%, ages 13-18, 67% Latino, 66% female). Body composition was determined by dual energy X-ray absorptiometry, abdominal fat depots [VAT, subcutaneous (SAT)] by multiple-slice MRI, time-controlled serum sample to measure cortisol, and 2-day multi-pass 24-hour dietary recall. Linear regression analysis examined the cross-sectional relationship between cortisol, and the interaction of diet and cortisol on adiposity measures. Sex, race, age, and total body fat were a priori covariates. RESULTS There was a significant interaction between cortisol and sugar (total and added) in the prediction of VAT (P(interaction) ≤ 0.05). Amongst participants with high total or added-sugar intake, cortisol was significantly associated with VAT (ß = 0.031 P < 0.001; ß = 0.026 P < 0.001), with no relationship in low consumers of total or added-sugar. CONCLUSION Dietary sugar may play an important role in modifying the relationship between cortisol and VAT, such that cortisol is significantly associated with elevated VAT under conditions of high sugar intake.