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Background: The optimal macronutrient composition of the diet is controversial and many adults attempt to regulate the intake of specific macronutrients for various health-related reasons., Objective: The objective was to compare stability and ranges of intakes of different macronutrients across diverse adult populations in the USA and globally., Methods: US dietary intake data from NHANES 2009-2014 were used to determine macronutrient intake as a percentage of total energy intake. Variability in macronutrient intake was estimated by calculating the difference between 75th and 25th percentile (Q3-Q1) IQRs of macronutrient intake distributions. In addition, intake data from 13 other countries with per capita gross domestic product (GDP) over $10,000 US dollars (USD) were used to assess variability of intake internationally since there are large differences in types of foods consumed in different countries., Results: Protein, carbohydrate, and fat intake (NHANES 2009-2014) was 15.7 ± 0.1, 48.1 ± 0.1, and 32.9 ± 0.1% kcal, respectively, in US adults. The IQR of protein intake distribution (3.73 ± 0.11% kcal) was 41% of carbohydrate intake distribution (9.18 ± 0.20% kcal) and 58% of fat intake distribution (6.40 ± 0.14% kcal). The IQRs of carbohydrate and fat intake distributions were significantly (P <0.01) influenced by age and race; however, the IQR of protein intake was not associated with demographic and lifestyle factors including sex, race, income, physical activity, and body weight. International mean protein intake was 16.3 ± 0.2% kcal, similar to US intake, and there was less variation in protein than carbohydrate or fat intake., Conclusion: Protein intake of the US population and multiple international populations, regardless of demographic and lifestyle factors, was consistently ∼16% of total energy, suggesting biological control mechanism(s) tightly regulate protein intake and, consequently, influence intake of other macronutrients and food constituents. Substantial differences in intake of the other macronutrients observed in US and international populations had little influence on protein intake. This trial was registered at the ISRCTN registry as ISRCTN46157745 (https://www.isrctn.com/ISRCTN4615774)., (Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.)

Energy deficit and dietary macronutrient intake are thought to independently modulate cognition, mood and sleep. To what extent manipulating the dietary ratio of protein-to-carbohydrate affects mood, cognition and sleep during short-term energy deficit is undetermined. Using a randomized, block design, 39 non-obese young adults (21±1 years, BMI 25±1 kg/m(2)) consumed diets containing 0.8 g, 1.6 g or 2.4 g protein per kg body weight per day for 31 days. Carbohydrate intake was reduced to accommodate higher protein intakes while dietary fat was maintained at 30% of total energy intake. Cognitive performance, mood, self-reported sleep quality, and plasma amino acid concentrations were periodically assessed during a 10-day energy balance period and a subsequent 21-day, 40% energy deficit period. Anger, tension and total mood disturbance increased during the initial ten days of energy deficit (P<0.05), but by the end of the energy deficit returned to levels not different from those measured during energy balance. No effects of dietary protein-to-carbohydrate ratio on cognitive performance, mood or self-reported sleep quality were observed during energy balance or energy deficit. Thus, high-protein, low-carbohydrate, moderate-fat diets do not appear to benefit or impair cognition, mood or sleep in non-obese adults during energy deficit. These findings suggest that energy deficit may initially be psychologically difficult for non-obese individuals attempting to lose weight, but that these changes are transient. Employing strategies that alleviate decrements in mood during this initial period of adaptation may help sustain weight loss efforts., (Published by Elsevier Inc.)

Background: Protein supplements are consumed frequently by athletes and recreationally active adults for various reasons, including improved exercise performance and recovery after exercise. Yet, far too often, the decision to purchase and consume protein supplements is based on marketing claims rather than available evidence-based research., Objective: The purpose of this review was to provide a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements, when combined with carbohydrate, directly enhance endurance performance by sparing muscle glycogen during exercise and increasing the rate of glycogen restoration during recovery. The analysis was used to create evidence statements based on an accepted strength of recommendation taxonomy., Data Sources: English language articles were searched with PubMed and Google Scholar using protein and supplements together with performance, exercise, competition, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers., Study Selection: Inclusion criteria specified recruiting healthy active adults less than 50 years of age and evaluating the effects of protein supplements in combination with carbohydrate on endurance performance metrics such as time-to-exhaustion, time-trial, or total power output during sprint intervals. The literature search identified 28 articles, of which 26 incorporated test metrics that permitted exclusive categorization into one of the following sections: ingestion during an acute bout of exercise (n = 11) and ingestion during and after exercise to affect subsequent endurance performance (n = 15). The remaining two articles contained performance metrics that spanned both categories., Study Appraisal and Synthesis Methods: All papers were read in detail and searched for experimental design confounders such as energy content of the supplements, dietary control, use of trained or untrained participants, number of subjects recruited, direct measures of muscle glycogen utilization and restoration, and the sensitivity of the test metrics to explain the discrepant findings., Results: Our evidence statements assert that when carbohydrate supplementation was delivered at optimal rates during or after exercise, protein supplements provided no further ergogenic effect, regardless of the performance metric used. In addition, the limited data available suggested recovery of muscle glycogen stores together with subsequent rate of utilization during exercise is not related to the potential ergogenic effect of protein supplements., Limitations: Many studies lacked ability to measure direct effects of protein supplementation on muscle metabolism through determination of muscle glycogen, kinetic assessments of protein turnover, or changes in key signaling proteins, and therefore could not substantiate changes in rates of synthesis or degradation of protein. As a result, the interpretation of their data was often biased and inconclusive since they lacked ability to test the proposed underlying mechanism of action., Conclusions: When carbohydrate is delivered at optimal rates during or after endurance exercise, protein supplements appear to have no direct endurance performance enhancing effect.

Objective: Insulin-like growth factor-I (IGF-I) is a key regulator of metabolism during altered energy states. The IGF-I system components respond to prolonged caloric restriction but it is not clear if this system responds similarly to acute caloric restriction. The purpose of this study was to characterize the IGF-I system response to acute caloric restriction with a secondary purpose of determining if two isocaloric diets with different ratios of carbohydrate to fat alter the IGF-I system under conditions of caloric balance., Materials/methods: A double-blind, placebo-controlled crossover design was used in which 27 subjects underwent three, 48-h experimental treatments: 1) caloric restriction 2) carbohydrate and 3) carbohydrate/fat. Blood was sampled periodically (6 time points total) for IGF-I (total and free), IGFBPs1-4, insulin and glucose. ANOVAs were used with significance set at P<0.05., Results: Total IGF-I decreased 7% during CR (P=0.051) and remained stable during CHO and CHO/F. Free IGF-I decreased 43% during CR (P<0.05) and remained stable during CHO and CHO/F. IGFBP-1 increased by 445% during CR (P<0.05) compared to CHO and CHO/F with no changes for IGFBP-2, IGFBP-3 and IGFBP-4. There was no change in glucose or insulin during CR over the course of the study. Insulin and glucose increased (P<0.05) after a meal in both the CHO and CHO/F groups with no difference between these two groups., Conclusion: Our findings indicate that free IGF-I decreases and IGFBP-1 increases during caloric restriction, but they are not altered with diets differing in carbohydrate and fat content. Changes in free IGF-I and IGFBP-1 are sensitive to caloric restriction, and their measurement may be valuable in monitoring the physiological response to refeeding in those consuming suboptimal calories., (Published by Elsevier Inc.)

Energy-restricted low glycemic load diets are being used increasingly for weight loss. However, the long-term effects of such regimens on mood and cognitive performance are not known. We assessed the effects of low glycemic load (LG) and high glycemic load (HG) energy-restricted diets on mood and cognitive performance during 6 months of a randomized controlled trial when all food was provided. Subjects were 42 healthy overweight adults (age 35+/-5 years; BMI 27.8+/-1.6 kg/m(2)) with a mean weight loss of 8.7+/-5.0% that did not differ significantly by diet randomization. Mood was assessed by using the Profile of Mood States (POMS) questionnaire. Cognitive performance was assessed by using computerized tests of simple reaction time, vigilance, learning, short-term memory and attention, and language-based logical reasoning. Worsening mood outcome over time was observed in the HG diet group compared to the LG for the depression subscale of POMS (p=0.009 after including hunger as a covariate). There was no significant change over time in any cognitive performance values. These findings suggest a negative effect of an HG weight loss diet on sub-clinical depression but, in contrast to a previous suggestion, provide no support for differential effects of LG versus HD diets on cognitive performance.

Objective: The goal of this project was to evaluate the effects of energy supplementation, as liquid carbohydrate (CHO), on facilitating recovery of cognitive function in soldiers who have been exposed to sustained psychological and physical stress during Survival School Training. PROJECT DESIGN: A double-blind, placebo-controlled design was used. Healthy, male volunteers attending survival training were recruited for participation in the study. At the conclusion of the mock captivity phase of survival training and before a recovery night of sleep, subjects participated in cognitive testing. After this, subjects were randomly assigned to one of three treatment groups. Subjects received either a 6% CHO (35.1 kJ/kg), 12% CHO (70.2 kJ/kg), or placebo beverage in four isovolemic doses. In the morning of the following day, all subjects participated in a second assessment of cognitive functioning., Results: Compared to subjects who received placebo, those who received supplemental CHO beverages exhibited significantly improved performance on a complex cognitive task (i.e., Stroop Test) involving concentration effectiveness associated with selective attention and response inhibition. No differences were observed on a variety of cognitive tasks of lesser complexity., Discussion: These data suggest nutritional interventions enhance the rapid recovery of complex cognitive functions impaired by exposure to significant or sustained stressful conditions. In addition to enhancing speed of recovery of function between operational intervals, the current data suggest that dietary supplement strategies may hold promise for enhancing field performance and a capacity to assist in sustaining operations by military personnel over time.

This study examined effects of a single protein-free (PROT-free), high carbohydrate meal (0% protein, 82% carbohydrate) or control meal (20% protein, 62% carbohydrate) on coping behavior and neurotransmitter levels of male Fischer 344 rats. Meals varying in protein/carbohydrate ratio differentially affect transport of neurotransmitter precursors into the brain and alter neurotransmission. The meals were studied in animals exposed to heat stress and normothermic control animals. Coping behavior was assessed using the Porsolt swim test (N = 39). In other rats, dopamine (DA), epinephrine (EPI), norepinephrine (NE) and serotonin in the striatum were assessed using in vivo microdialysis (N = 35). In control-fed rats, heat stress impaired Porsolt performance in comparison to normothermic controls (p <0.05). The PROT-free, high carbohydrate meal protected animals from adverse effects of stress on coping performance as it reduced the effect of heat stress more than 90%. Significant changes in striatal DA and EPI efflux were observed as a consequence of the nutritional manipulation and heat exposure. It is concluded a single PROT-free, high carbohydrate meal improves ability to cope with heat stress and alters neurotransmission. The neurochemical basis for these effects may be a change in DA efflux, although other mechanisms cannot be ruled out.

Background: The brain requires a continuous supply of glucose to function adequately. During aerobic exercise, peripheral glucose requirements increase and carbohydrate supplementation improves physical performance. The brain's utilization of glucose also increases during aerobic exercise. However, the effects of energy supplementation on cognitive function during sustained aerobic exercise are not well characterized., Objective: The effects of energy supplementation, as liquid carbohydrate, on cognitive function during sustained aerobic activity were examined., Design: A double-blind, placebo-controlled, between-subjects design was used. Young, healthy men (n = 143) were randomly assigned to 1 of 3 treatment groups. The groups received either a 6% (by vol) carbohydrate (35.1 kJ/kg), 12% (by vol) carbohydrate (70.2 kJ/kg), or placebo beverage in 6 isovolumic doses, and all groups consumed 2 meals (3200 kJ). Over the 10-h study, the subjects performed physically demanding tasks, including a 19.3-km road march and two 4.8-km runs, interspersed with rest and other activities. Wrist-worn vigilance monitors, which emitted auditory stimuli (20/h) to which the subjects responded as rapidly as possible, and a standardized self-report mood questionnaire were used to assess cognitive function., Results: Vigilance consistently improved with supplemental carbohydrates in a dose-related manner; the 12% carbohydrate group performed the best and the placebo group the worst (P < 0.001). Mood-questionnaire results corroborated the results from the monitors; the subjects who received carbohydrates reported less confusion (P = 0.040) and greater vigor (P = 0.025) than did those who received the placebo., Conclusions: Supplemental carbohydrate beverages enhance vigilance and mood during sustained physical activity and interspersed rest. In addition, ambulatory monitoring devices can continuously assess the effects of nutritional factors on cognition as individuals conduct their daily activities or participate in experiments.

Background: Nutritional intake by military personnel is typically inadequate during field exercises, potentially compromising health and performance., Hypothesis: Drinking a supplemental carbohydrate (CHO) beverage will increase total caloric intake and maintain nutritional status during military training in the desert., Methods: A total of 63 volunteers were randomly assigned to one of two groups to receive either a CHO or placebo beverage with military rations during an 11-d desert field exercise. Fluid intake was ad libitum and adequate rations were provided. Blood samples were collected twice to assess nutritional status, and nutrient intake was determined with consumption data. Mood state was examined by questionnaire., Results: Energy intake was significantly higher in the CHO group (3050 kcal x d(-1) vs. 2631 kcal x d(-1)), with additional CHO from the beverage providing energy with some compensation by reduced fat and protein intake. Intakes of energy, folacin, calcium, magnesium, iron, and zinc in both groups were inadequate, with intakes significantly lower (p<0.05) for calcium, magnesium, and zinc in the CHO beverage group. Blood parameters of nutritional status remained within normal ranges with no differences between groups, but significant decreases were seen in pre-albumin. No changes in mood were seen during the training, nor after exposure to desert conditions., Conclusions: The operational ration supplemented with a CHO beverage significantly increases CHO and energy intakes compared with standard rations and maintains nutritional status for short exercises. Fortification with micronutrients most at risk for deficient intake from foods may be needed for longer deployments.

Two groups of obese individuals who consume excessive calories primarily as snack foods have been identified. Carbohydrate cravers consume most or all snacks as carbohydrate-rich foods despite the equal accessibility of protein-rich snacks. Noncarbohydrate cravers consume about equal amounts of protein- and carbohydrate-rich snack foods. Using standardized self-report questionnaires, we measured mood before and 2 h after consumption of a high-carbohydrate lunch (104 g CHO). Responses to the meal differed significantly: noncarbohydrate cravers reported feeling considerably less alert, more fatigued and sleepy, while carbohydrate cravers described little or no change in these aspects of mood. Moreover, noncarbohydrate cravers experienced an increase in depression, while carbohydrate cravers reported feeling less depressed. Findings suggest that snacking habits of obese individuals may be related to subsequent mood states.

It is well established that the ratio of the plasma tryptophan concentration to those of the other large neutral amino acids determines the transport of tryptophan into the brain. Brain tryptophan levels, in turn, control production of the neurotransmitter serotonin. Protein-rich meals, when consumed in the morning after an overnight fast, have been shown to decrease the plasma tryptophan ratio, while carbohydrate-rich meals have the opposite effect. We now show that these meals have similar effects when consumed for lunch, even if they are preceded by a small breakfast meal.