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Effect of exercise and recovery on muscle protein synthesis in human subjects. Coyle EF. Fluid and fuel intake during exercise. The rate of protein digestion affects protein gain differently during aging in humans. J Physiol Pt 2 — Regulation of protein synthesis after acute resistance exercise in diabetic rats. When does energy deficit affect soldier physical performance? Net postprandial utilization of [ 15 N]-labeled mild protein nitrogen is influenced by diet composition in humans. J Nutr 4 — Availability of eIF4E regulates skeletal muscle protein synthesis during recovery from exercise.

The influence of adaptation to physical effort on nitrogen balance in man. Nutr Rept Intern — Pre-exercise carbohydrate and fat ingestion: Effects on metabolism and performance. Time course evaluation of protein synthesis and glucose uptake after acute resistance exercise in rats.

J Appl Physiol 88 3 — Muscle glycogen in soldiers on different diets during military field manoeuvres. Aviat Space Environ Med 54 10 — Regulation of protein synthesis by branched-chain amino acids. Invited review: Role of insulin in translational control of protein synthesis in skeletal muscle by amino acids or exercise. J Appl Physiol 93 3 — A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. Independent and combined effects of amino acids and glucose after resistance exercise. Med Sci Sports Exerc 35 3 — Nitrogen homeostasis in man: The diurnal responses of protein synthesis and degradation and amino acid oxidation to diets with increasing protein intakes.

Clin Sci 86 1 — Mixed muscle protein synthesis and breakdown after resistance exercise in humans. Resistance training reduces the acute exercise-induced increase in muscle protein turnover. Eating in combat: A survey of US Marines. Mil Med 12 — Nitrogen homeostasis in man: Influence of protein intake on the amplitude of diurnal cycling of body nitrogen. Nitrogen homoeostasis in man: Diurnal changes in nitrogen excretion, leucine oxidation and whole body leucine kinetics during a reduction from a high to a moderate protein intake.

Clin Sci 86 2 — Quantitative effect of an isoenergetic exchange of fat for carbohydrate on dietary protein utilization in healthy young men. Am J Clin Nutr 32 11 — Exercise, protein metabolism, and muscle growth. Acute response of net muscle protein balance reflects h balance after exercise and amino acid ingestion. Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise.

Med Sci Sports Exerc 36 12 — Postexercise net protein synthesis in human muscle from orally administered amino acids. Nitrogen balance in men with adequate and deficient energy intake at three levels of work. The Committee on Optimization of Nutrient Composition of Military Rations for Short-Term, High-Stress Situations was charged with making recommendations on the composition of a food ration assault ration that will best sustain physical and cognitive performance for short-term use by highly-trained soldiers during high-tempo, stressful, repetitive combat missions; in addition, the food ration will also prevent possible adverse health consequences under the conditions of a hypocaloric diet.

Stress may be due to high physical and cognitive workloads such as exercise, extreme environmental temperature, dehydration, heat exhaustion, threat to personal safety, sleep deprivation, and other operational demands. Important health concerns for soldiers during combat missions are the optimization of gastrointestinal processes and prevention of diarrhea, dehydration, hyperthermia, kidney stones; optimization of the function of immune system; and prevention of infections.

This paper focuses on several aspects of the design of such a ration. Although a lot of the literature presented is from the sports and exercise community, their conclusions can be used to support recommendations for the assault ration described above. This paper attempts to answer the following questions:. What would be the optimal amount of carbohydrates for an assault ration to enhance performance during combat missions? How much is performance going to decline when there is a reduction in both carbohydrates and calories? Costill and. Miller emphasized the need for fluid intake during exercise but recommend against ingesting very much carbohydrate.

This recommendation is understandable for that period of time, given that the physiological benefits of fluid replacement were beginning to be established, as reflected in the American College of Sports Medicine ACSM position-statement, whereas the physiological benefits of carbohydrate ingestion for blood glucose supplementation as well as the physiological mechanisms explaining this benefit were not yet established Hargreaves, In the s, the observation that adding carbohydrate to water temporarily slowed the gastric emptying rate was interpreted to suggest that fluid replacement solutions should not contain much carbohydrate Coyle et al.

Carbohydrate ingestion can delay muscle fatigue during prolonged cycling and running, and it also improves the power output that can be maintained Hargreaves, ; Millard-Stafford, ; Millard-Stafford et al. It is now understood that the slight slowing of gastric emptying caused by solutions containing up to 8 percent of carbohydrate is a relatively minor factor in fluid replacement rate compared with the large influence of increased fluid volume for increasing gastric emptying and fluid replacement rate Coyle and Montain, a, b; Maughan, ; Maughan and Noakes, ; Maughan et al.

The type of carbohydrate can be glucose, sucrose, maltodextrins, or some high-glycemic starches. Fructose intake should be limited to amounts that do not cause gastrointestinal discomfort Casa et al. Benefits of carbohydrate ingestion during performance of high-intensity, intermittent exercise attempted after at least 60 minutes of continuous moderate-intensity exercise i. Power output measured over 5 to 15 minutes of high-. During the past decade, attention has focused on determining if carbohydrate intake during sporting events such as soccer and tennis improves various indices of performance.

Physiological mechanisms for this ergogenic effect of carbohydrate ingestion are not clear and have been theorized to involve more than simply skeletal muscle metabolism, implying a neuromuscular component. The challenges now are identifying the types of physical activity and sporting situations during which carbohydrate ingestion is advisable and those during which such a recommendation is not effective or even counterproductive. Performance or fatigue resistance can be governed by numerous physiological factors involving, primarily, the skeletal muscle, the cardiovascular system, and the nervous system.

Some primary causes of fatigue are not influenced by carbohydrate ingestion during exercise; for example, the negative effects of hyperthermia on performing prolonged exercise in a hot environment [e. However, during exercise in a cool environment [i. Under conditions not eliciting hyperthermia, the most important factor for performing prolonged, intense exercise appears to be maintaining carbohydrate availability and thus carbohydrate oxidation, especially from blood glucose oxidation as muscle glycogen concentration declines.

This goal was better achieved by ingesting 7 percent carbohydrate solutions as compared with a 14 percent solution Febbraio et al. Another example of a condition when carbohydrate ingestion during exercise would not be expected to improve performance is when the cause of fatigue is the accumulation of hydrogen ion in skeletal muscle e. Performing exercise that is not sufficiently stressful to cause fatigue, as evidenced by reduced power production, or that does not require high levels of effort to maintain power, as reflected, for example, by high levels of various stress hormones, would not benefit from carbohydrate ingestion.

Furthermore, carbohydrate intake is not generally recommended during events, performed either continuously or intermittently, that are completed in 30 to 45 minutes or less. Although this last concept has not been extensively studied to date, it is a valid assumption based on the practices of athletes competing in events lasting only 30 to 45 minutes. As discussed, carbohydrate ingestion does not appear to lessen fatigue from hyperthermia or dehydration-induced hyperthermia, even when the durations of exercise are prolonged e.

Thus, there does not appear to be any benefit of adding carbohydrate to fluid replacement solution under these conditions. Accordingly, people who exercise at moderate intensity for less than one hour and do not experience fatigue do not appear to benefit from carbohydrate ingestion during exercise. Carbohydrate ingestion during prolonged exercise can benefit performance if inadequate carbohydrate energy from blood glucose is the cause of fatigue Coggan and Coyle, ; Febbraio et al.

This effect on performance is a well-documented physiological mechanism by which the ergogenic benefit of carbohydrate ingestion during exercise can be explained. However, carbohydrate ingestion has been observed to improve performance under conditions in which fatigue is not clearly caused by a lack of aerobic or anaerobic carbohydrate energy.

For example, when the duration of continuous exercise is extended to approximately 60 minutes and thus the intensity is 80 to 90 percent VO 2 max, carbohydrate ingestion during exercise has been shown to improve power output by 6 percent during the to minute period Below et al. Other recent studies have also reported a performance benefit of carbohydrate feeding when the total duration of the performance bout is approximately 60 minutes or more by breaking the time into shorter exercise durations, thereby simulating the demands of many sports basketball, soccer, hockey in which high-intensity exercise is interspersed with periods of recovery Mitchell et al.

The total duration of these work—rest bouts was more. The physiological mechanisms responsible for these performance benefits from carbohydrate ingestion are not clear and have been theorized to involve the central nervous system, skeletal muscle, and the cardiovascular system. It is likely that carbohydrate feeding influences the interactions of all three systems, possibly through the actions of neurotransmitters, hormones, and peptides that are already known e.

Regardless, sufficient evidence is accumulating to recommend carbohydrate ingestion during exercise bouts of continuous or intermittent exercise that lasts for 60 minutes or longer and cause fatigue from factors other than hyperthermia. Carbohydrate ingestion should be used with caution during events lasting approximately 15 to 45 minutes and requiring repeated bouts of intense exercise lasting several minutes followed by several minutes of rest because these events may cause large swings in blood glucose and insulin concentration.

Feeding plans must be specific to the varied intensity and time demands of the event. Those feeding schedules might be more than those described below, yet without data or experience to make more specific recommendations; all that can be done at present, besides recognizing these limitations, is to encourage systematic trial and error. The goal of the feeding schedule should be to create a steady flow of carbohydrate into the blood stream, which will then provide a steady flow of exogenous glucose into the blood.

In other words, if carbohydrate feeding is begun during an event, it should be continued throughout the event in a manner that allows for a steady flow of exogenous glucose into the blood with minimal gastrointestinal discomfort.

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Avoid giving a large bolus of carbohydrate i. This practice will prime the body for glucose metabolism, reduce fat oxidation, and then deprive the body of the fuel it has been primed to metabolize. There is not a clear physiological need to consume any fluid or fuel when beginning exercise while reasonably hydrated and proceeding to exercise at low or moderate intensity for less than one hour without experiencing undo fatigue. However, there is no apparent reason for people to avoid fluid or carbohydrate intake if this is their preference and is well tolerated.

Portions of this manuscript are similar to a recent review by the author published in Journal of Sports Sciences — Fluid and carbohydrate ingestion independently improve performance during 1 h of intense exercise. Med Sci Sports Exerc 27 2 — J Athlet Train 35 2 — Effect of carbohydrate feedings during high-intensity exercise.

J Appl Physiol 65 4 — Carbohydrate ingestion during prolonged exercise: Effects on metabolism and performance. Exerc Sport Sci Rev — Med Sci Sports Exerc 28 1 :i—vii. Costill D, Miller J. Nutrition for edurance sports. Carbohydrate and fluid balance. Int J Sports Med — Benefits of fluid replacement with carbohydrate during exercise.

Carbohydrate and fluid ingestion during exercise: Are there trade-offs? Med Sci Sports Exerc 24 6 — Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate. J Appl Physiol 61 1 — Gastric emptying rates for selected athletic drinks. Res Q 49 2 — Carbohydrate drinks delay fatigue during intermittent, high-intensity cycling in active men and women.

Int J Sport Nutr 7 4 — Effects of carbohydrate and chromium ingestion during intermittent high-intensity exercise to fatigue. Effects of branched-chain amino acids and carbohydrate on fatigue during intermittent, high-intensity running. Int J Sports Med 20 5 — Effect of CHO ingestion on exercise metabolism and performance in different ambient temperatures. Med Sci Sports Exerc 28 11 — Water and carbohydrate ingestion during prolonged exercise increase maximal neuromuscular power. J Appl Physiol 88 2 — The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment.

J Sports Sci 18 5 — Hargreaves M. Carbohydrates and exercise performance. Nutr Rev 54 4 Pt 2 :S—S Maughan RJ. Fluid and electrolyte loss and replacement in exercise. J Sports Sci 9 Spec No — Fluid replacement and exercise stress. A brief review of studies on fluid replacement and some guidelines for the athlete. Sports Med 12 1 — Fluid replacement in sport and exercise—A consensus statement.

Br J Sport Med 27 1 Millard-Stafford M. Fluid replacement during exercise in the heat. Review and recommendations. Sports Med 13 4 — Water versus carbohydrate-electrolyte ingestion before and during a km run in the heat. Int J Sport Nutr 7 1 — Influence of carbohydrate dosage on exercise performance and glycogen metabolism.

J Appl Physiol 67 5 — The effect of fluid and carbohydrate feedings during intermittent cycling exercise. Med Sci Sports Exerc 19 6 — Influence of ingesting a carbohydrate-electrolyte solution on endurance capacity during intermittent, high-intensity shuttle running.

J Sports Sci 13 4 — Rehrer NJ. The maintenance of fluid balance during exercise. Int J Sports Med 15 3 — Effects of electrolytes in carbohydrate beverages on gastric emptying and secretion. Med Sci Sports Exerc 25 1 — Gastric emptying, absorption, and carbohydrate oxidation during prolonged exercise. J Appl Physiol 72 2 — Sugiura K, Kobayashi K. Effect of carbohydrate ingestion on sprint performance following continuous and intermittent exercise.

Med Sci Sports Exerc 30 11 — Oxidation rates of orally ingested carbohydrates during prolonged exercise in men. J Appl Physiol 75 6 — Med Sci Sports Exerc 34 4 — The importance of nutrition for cognitive performance in military settings has long been recognized. Cognitive performance refers to intellectual behaviors such as memory, reasoning, attention, vigilance, and choice reaction time.

Mood e. The aspects of cognition that are important in combat settings include the ability to perceive, attend to, and respond appropriately to cues; make prompt decisions; and sustain vigilance IOM, ; Mays, The Committee on Optimization of Nutrient Composition of Military Rations for Short-Term, High-Stress Situations, an ad hoc committee of the CMNR, has been given the task of recommending the nutrient composition of a ration for combat missions to optimize physical and cognitive performance and to prevent adverse health consequences.

This daily ration is intended for repeated short-term use three to seven days followed by one to three days of ad libitum recovery by fit male soldiers during high-tempo, stressful combat missions. Stress may be caused by physical and cognitive workloads, extreme temperature, threats to safety, and sleep deprivation, all of which can interfere with cognitive performance Lieberman et al. The purpose of this report is to briefly review relevant evidence on the effects of energy and macronutrients i.

Because factors associated with combat operations are likely to lead to cognitive deficits relative to normal functioning, the realistic goal in optimizing the nutrient composition of the ration should be to decrease these deficits, rather than to enhance performance beyond normal bounds. What would be the optimal macronutrient balance between carbohydrate, protein, and fat for such an assault ration to enhance cognitive performance during combat missions?

For the purpose of this paper, it has been assumed that other nutrional requirements of the soldiers e. If these other requirements are not met, the results could override the importance of macronutrient requirements. For instance, it is well established that hypohydration Wilson and Morley, and iron deficiency Sandstead, present significant detriments to cognitive performance. In the combat situation, particularly during extreme temperatures, the highest priority for reducing cognitive impairment is adequate hydration IOM, The maximum weight of the macronutrient component of a 1, gram-ration is approximately g [calculated from a standard, approximately 2,kcal ration, comprising 50 percent of energy as carbohydrate g , 30 percent as fat 80 g , and 20 percent as protein g ], with the remaining g comprised of noncaloric components, including moisture, fiber, and micronutrients.

Theoretically, g could provide between 2, kcal i. The question is: Should the energy content of the ration be maximized, or is there a more optimal ratio of macronutrients for cognitive performance? The acute effects hours of energy ingestion on cognitive performance have been examined in a number of studies in healthy, nonstressed subjects. Several reviews of the literature have concluded that the provision of energy in the morning breakfast generally improves cognitive performance over the next 30 minutes to 2 h, compared with no energy provision, with more robust effects on tests of memory and less consistent effects on tests of attention or vigilance Bellisle et al.

Green, ; Pollitt and Matthews, The mechanism for these results has not been elucidated, but likely both gut-mediated and centrally acting postabsorptive signals are involved Kaplan et al. By contrast to the breakfast studies, large meals provided at mid-day lunch consistently impair cognitive performance e. A few studies have examined the short-term effects of energy intake on cognitive performance and mood under stressful conditions, showing the benefits of increased energy intake.

One study found no changes in mood after low-energy intake during breakfast and lunch kcal as compared with a higher energy intake 1, kcal; consistent with energy needs of the subjects during a nonstressful condition Macht, However, when participants were subjected to emotionally stressful white noise, those with a low-energy intake experienced a degradation in mood i.

Another study strongly supports a beneficial effect of increased energy ingestion on cognitive performance and mood under stressful conditions Lieberman et al. In this study, male subjects from an elite combat unit were tested during periods of intense physical activity over 10 h, during which energy needs were not met with regular meals approximately kcal Lieberman et al. Energy supplementation carbohydrate-containing drink throughout the day improved vigilance and mood i.

The strongest effects on performance resulted from the highest energy drink approximately 1, kcal , followed by the medium-energy drink approximately kcal , and the placebo 0 kcal Figure B It is impossible to determine from this study whether the beneficial effects were caused by an increase in energy ingestion or an increase in carbohydrate ingestion.

The medium-term effects days of dieting to lose weight consistently impair cognitive performance and mood Leigh Gibson and Green, The effects are attributed to the act of dieting, rather than to inherent differences between dieters and nondieters because the impedence on performance is not observed when the same individuals are not dieting Green and Rogers, It has been suggested that this impairment is caused more by a psychological pre-occupation with food and feelings of hunger than by a physiologic effect of low. FIGURE B-9 Vigilance performance of soldiers who received carbohydrate CHO beverages or placebo in addition to regular meals providing approximately kcal while engaging in various activities over 10 h.

American Society for Clinical Nutrition. This conclusion is based on evidence that 1 individuals perform worse on cognitive tests when they are dieting, even when no actual weight is lost; 2 the magnitude and structure of the deficits is comparable to those caused by anxiety and depression; and 3 performance is not clearly affected by weight loss in the absence of other stress.

It has been hypothesized that task-irrelevant feelings of hunger and thoughts of food may impair performance by interfering with normal working memory function. A study using a similar eating pattern as would be consumed by combat soldiers several days of hypocaloric intake followed by ad libitum intake supports the hypothesis that energy restriction impedes performance in the absence of significant weight loss Laessle et al.

During the low-calorie periods, subjects reported stronger feelings of hunger and thoughts about food as well as demonstrating. Repeated episodes of low energy intakes over the 4 weeks did not reduce feelings of hunger. The implication of this study is that the negative effects of hunger are unlikely to be reduced during periods of low energy intake when soldiers repeatedly eat hypocaloric diets followed by ad libitum recovery periods.

In other words, it may be very difficult to train soldiers to ignore their hunger feelings. It should be noted, however, that this study was performed with women and not under the unique added stressors of combat missions. The hypothesis presented suggests that psychological feelings of hunger contribute to cognitive deficits during periods of low energy intake; however, the physiologic consequences of low energy intake and negative energy balance cannot be ruled out as contributing factors because other acute evidence presented earlier and longer term evidence under the stressful conditions presented below do not clearly indicate the mechanism involved.

Most likely, both psychological and physiological factors associated with low energy intake, particularly under stressful conditions, contribute to the performance deficit. The evidence that increased appetite interferes with the ability to perform optimally suggests that reducing hunger may be beneficial for mood and cognitive performance. Indeed, declining hunger sensations have been associated with being more energetic, lively, calm, and relaxed Fischer et al.

The macronutrient composition of foods can play an important role in minimizing hunger. Protein consistently and robustly induces greater satiety than carbohydrate or fat on a per calorie basis Westerterp-Plantenga, and has a greater effect on satiety than do substantially higher energy intakes from the other macronutrients Stubbs and Whybrow, ; Stubbs et al.

Carbohydrate appears to induce greater satiety than fat does on a per calorie basis Stubbs et al. Thus, to reduce the negative effects of hunger on cognitive performance and mood, it may be beneficial to increase the protein content of hypocaloric military rations and to reduce the fat content. Various types of each macronutrient also have different effects on satiety Stubbs et al.

A review concluded that high glycemic index carbohydrates i. However, these effects are not likely caused entirely by changes in blood glucose Kaplan and Greenwood, The data implicating different effects of fat type on satiety are mixed, with some suggesting that polyunsaturated fatty acids have a stronger effect on increasing satiety than monounsaturated or saturated fatty acids do French and Robinson, ; Lawton et al.

Medium-chain triglycerides, which are rapidly metabolized, have been shown to exert a stronger effect on satiety than long-chain triglycerides do; however, only a few human studies are available and the results are inconclusive French and Robinson, ; St-Onge and Jones, Research on the effects of protein type on satiety is also limited because evidence in human studies suggesting that some proteins might suppress appetite more than others is inconsistent Anderson and Moore, ; Westerterp-Plantenga, It is important to note that, although it is argued here that reducing hunger in soldiers consuming hypocaloric rations may be beneficial for cognitive performance, this may not be relevant if appetite is suppressed by hypohydration, physical activity, or stress to the extent that feelings of hunger and thoughts of food are eliminated.

It is well documented that soldiers tend to underconsume foods, and this may be partially due to a suppression of appetite IOM, Thus, it is important to determine whether the expected increase in appetite. There is evidence, however, that when military rations provide only 60 percent of energy needs i. The long-term effects weeks or months of energy intake on cognitive performance are not relevant if soldiers are able to consume enough excess energy during the one- to- three-day ad libitum recovery period to make up for the negative energy balance during the three to seven days, such that they do not lose weight.

By contrast, if soldiers are in a state of negative energy balance over weeks and months because of repeated consumption of hypocaloric diets and inadequate recovery periods, then the long-term effects of low energy intake are relevant. Evidence on the long-term effects of low energy intake on cognitive performance shows that those effects are minimal in the absence of significant stress but are significant if stress is present. In a review of the effects of underconsumption of military rations on cognitive performance, Mays concluded that underconsumption leading to weight loss up to 6 percent over 10 to 45 days does not affect performance in the absence of significant stress.

A more recent study over a day trial supports this conclusion Shukitt-Hale et al.


However, consistent with the long-term dieting data e. Based on the available data, Mays proposed a relationship between long-term negative energy balance and cognitive performance Figure B These data suggest that consumption levels of 75 to 90 percent of requirements may actually enhance performance in the first 3 to 15 days, whereas consumption of 50 percent or less of requirements degrades performance, particularly under stressful conditions.

Over the longer term, performance continues to degrade along with negative energy balance. Thus, if repeated short-term periods of low energy intake during combat operations lead to long-term negative energy balance, deficits in cognitive performance can be expected. FIGURE B Proposed relationship between energy intake as a percentage of energy expenditure and cognitive performance over two months, based on the results of several studies. It does not include dietary fiber, resistant starch, or other nondigestible carbohydrates that do not provide energy as a carbohydrate.

A large number of studies conducted over the past 20 years have shown beneficial effects of glucose ingestion on cognitive performance as compared with noncaloric sweetened placebos e. Cognitive impairments associated with hypoglycemic episodes have also been a consistent finding. McCall, Since that time, others have shown that consuming glucose can improve performance in young adults if cognitive tasks are sufficiently demanding Benton, ; however, the magnitude of the effects depends on glucose regulation and baseline cognitive abilities Awad et al.

The beneficial effects of consuming glucose are dependent on the type of cognitive test, task difficulty, and glucose dose Greenwood, ; Messier, In contrast with the data showing the benefits of eating breakfast and the detriments of eating lunch, the effects of consuming glucose appear to be positive in both the morning and the afternoon Sunram-Lea et al.

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The effects of glucose are strongest on functions mediated by the medial temporal lobe and surrounding areas, including long-term verbal memory, and less robust for other tasks, including short-term memory, attention, and reaction time. Glucose consumption can, however, improve performance on a wide range of tasks as long as the tasks are of sufficient difficulty.

For instance, Kennedy and Scholey found glucose ingestion improved performance in young adults on a difficult test serial sevens, which requires subjects to count backwards by sevens , but not on two easier tests Figure B These findings suggest that an increased brain requirement for glucose is needed before benefits of glucose ingestion can be observed.

Conditions for which glucose could reverse deficits in performance caused by increased brain requirements for glucose include those of aging McNay and Gold, , increased cognitive demand Fairclough and Houston, , and physical activity Brun et al. Thus, carbohydrate ingestion is likely to benefit cognitive performance during combat operations for which brain glucose requirements would likely be increased because of the demanding nature of the tasks and high levels of physical activity.

The dose of glucose that enhances cognitive performance follows an inverted U-shaped response in humans and animals. Consistently, low doses have no effect on performance, intermediate doses 25 to 75 g improve performance, and high doses have no effect or impair performance Greenwood, ; Greenwood et al. Taken together, these findings suggest that a moderate amount of glucose improves performance on a range of demanding cognitive tests in young adults, or on tasks in demanding situations e.

There is no consensus on the mechanism that explains the effects of glucose on cognitive performance, but several hypotheses have been proposed. The following effects of glucose ingestion have been most commonly suggested as. FIGURE B Mean number of responses subtractions or words produced made on each of three tasks after ingestion of noncaloric saccharin-sweetened placebo or of 25 g glucose drinks. As noted earlier, one study found that a carbohydrate-containing beverage provided in addition to regular hypocaloric meals benefited vigilance and mood during combat training Figure B-9 , but it is impossible to determine whether the benefits were due to increased energy intake or to carbohydrate intake Lieberman et al.

The authors suggested that the benefits could have been due to an increased supply of glucose to the brain, which could have helped. FIGURE B Logical memory scores in elderly subjects 5 and 40 minutes after glucose ingestion, presented as differences from placebo saccharin. Significant memory enhancement was observed after 25 g glucose, but not at the higher or lower doses.

Other studies suggest that carbohydrate, independent of energy intake, benefits performance under hypocaloric Wing et al. Under nonexercise, adequate energy situations, carbohydrate ingestion has been associated with both better and worse moods Benton, ; Leigh Gibson and Green, , which may be dependent on the testing time after ingestion. Carbohydrate may improve mood up to 30 minutes after ingestion, but it is. However, the effect of carbohydrate on serotonin is abolished with the ingestion of as little as 4-percent protein Benton, ; Benton and Donohoe, ; Benton and Nabb, ; Spring et al.

Another hypothesis suggests that beneficial effects of carbohydrate on mood are related to an increased release of endorphins relevant to the ingestion of any palatable food, rather than to carbohydrate per se Benton, The type of carbohydrate may be important for cognitive performance although research in this area is limited to two studies. In one study in healthy elderly subjects, 50 g of carbohydrate from glucose, potato high glycemic index , or barley low glycemic index all improved performance on memory and a test of general brain function up to one hour after ingestion, particularly in subjects with poorer baseline memory and glucose regulation Kaplan et al.

These findings were supported by a recent study that found that a high-carbohydrate meal with a lower glycemic index improved memory in young adults up to 3 h after ingestion, but a higher glycemic index meal did not Benton et al. The findings could not be related to blood glucose levels, but these data, along with the evidence showing an inverted U-shaped dose response for glucose, suggest that a prolonged increase in blood glucose and insulin levels, rather than rapid fluctuations, may be beneficial.

It is noteworthy that virtually all studies examining the effects of carbohydrate on cognitive performance or mood have used glucose or glucose polymers e. A few studies have examined the effects of fructose which is metabolized differently from glucose, in rats, but the evidence is mixed Messier, Until evidence to the contrary is available in humans, it should be assumed that the beneficial effects of carbohydrate are limited to sources of glucose or glucose polymers.

Protein has the potential to influence cognitive performance because several amino acids, including tryptophan, tyrosine, phenylalanine, arginine, histadine,. Indeed, individual amino acids have been shown to influence cognitive performance; however, these effects are likely not relevant when examining the effects of protein consumed as part of a food ration Greenwood, In particular, tyrosine benefits cognitive performance in sleep deprived, stressed subjects, likely by its role as a precursor for the neurotransmitters norepinephrine and dopamine Lieberman, Tryptophan may be beneficial as a sleep aid, by way of its effects on increasing synthesis of serotonin, and it improves vigilance by way of increasing the release of melatonin Lieberman, However, any potential benefits of these amino acids would likely be as between-meal supplements, rather than as part of normal meals Greenwood, As noted in the carbohydrate section above, several reports have concluded that high-carbohydrate—low-protein meals are sedating because they cause an increase in serotonin synthesis, whereas protein-rich meals are arousing and can improve reaction time and vigilance Dye and Blundell, ; IOM, ; Leigh Gibson and Green, However, as noted, these findings are likely not relevant for mixed macronutrient military rations because as little as 4 percent protein prevents the effect on serotonin.

Moreover, other data do not support a negative influence on mood by consumption of a high-carbohydrate—low-protein diet. A review by Benton and Donohoe concluded that diets higher in carbohydrate and lower in protein are associated with less depression, anger, and tension and with being more energetic. Although the fat content of diets can have an effect on cognitive performance over the long term i. Nevertheless, some studies have found acute effects of fat on performance and mood, but the data are inconsistent. Recent reviews concluded that in general, high-fat—low-carbohydrate meals can lead to declines in alertness and reaction time, particularly when they differ from habitual fat intake Dye and Blundell, ; Leigh Gibson and Green, Few direct comparisons between pure macronutrients have been made.

Kaplan and colleagues found that in healthy elderly persons, pure protein, carbohydrate, and fat could all improve memory performance 15 minutes after ingestion compared with a noncaloric placebo, suggesting a general benefit of energy ingestion, likely mediated by a peripheral mechanism, which could include gut peptides or signals to the brain by way of the vagus nerve. However, it was also found that each macronutrient had unique effects on performance.

For instance, as shown in Figure B , only glucose tended to improve memory 60 minutes after ingestion, and performance on a visual-motor task; and protein was the only macronutrient to slow the rate of forgetting. Various peripheral and. NOTE: Lower scores represent better performance. Another study also found unique effects of each macronutrient in healthy young adults Fischer et al. Carbohydrate improved choice reaction and short-term memory time after one hour; protein improved choice reaction time after two hours; fat improved performance on short-term memory and attention.

Taken together, several reviews have concluded that, although macronutrients have been shown to have different effects on cognitive performance, the effects have been inconsistent, and few overall conclusions can be made at this time about an optimal ratio of macronutrients for cognitive performance Bellisle et al. Despite discrepancies in the literature, some conclusions can be made about the effects of energy ingestion on cognitive performance. Thus, minimizing hunger may minimize the negative effects on performance. Hunger can be minimized with higher protein and lower fat ingestion.

The review of the research presented in this paper shows that the scientific literature in this area is inconsistant and contradictory; therefore, it is difficult to make definitive recommendations regarding the questions posed in the introduction. The research, although not conclusive, supports the following conclusions described below.

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The following are desired characteristics of an assault ration designed for cognitive performance:. Adequate and sustained glucose supply to the brain. The provision of glucose or carbohydrate to the brain improves mood and performance when brain glucose requirements increase, which appears to occur during cognitively demanding tasks, particularly under hypocaloric, stressful, or physically demanding conditions.

Moderate fluctuations in blood glucose.

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Consistent evidence shows that both hypoglycemia and hyperglycemia impair cognitive performance; that intermediate, but not high or low, doses of glucose improve performance;. Thus moderate, rather than extreme, fluctuations in blood glucose are desirable. Minimize feelings of hunger. Hypocaloric intakes are associated with deficits in cognitive performance and mood, and this is caused, in part, by feelings of hunger and thoughts of food interfering with normal cognitive processes. Reducing feelings of hunger is desirable.

Minimize long-term negative energy balance. Sufficient data indicate that long-term energy deficits resulting in negative energy balance and weight loss are associated with deficits in cognitive performance and mood under stressful situations. Long-term negative energy balance should be minimized. Plant Physiol.


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Metal enrichment experiments in the Weddell-Scotia Seas: effects of iron and manganese on various plankton communities. Iron III -siderophore coordination chemistry: reactivity of marine siderophores. The influence of temperature and pH on trace metal speciation in seawater. Overexpression and characterization of an iron storage and DNA-binding Dps protein from Trichodesmium erythraeum.

Oceanic phytoplankton, atmospheric sulfur, cloud albedo and climate. Effects of iron, manganese, copper, and zinc enrichments on productivity and biomass in the subarctic Pacific. Copper complexation in the northeast Pacific. Spatial and temporal variation of copper complexation in the North Pacific. Control of community growth and export production by upwelled iron in the equatorial Pacific Ocean. Southern ocean iron enrichment experiment: carbon cycling in high- and low-Si waters. Molybdenum in the northeast Pacific Ocean.

Influence of zinc and iron enrichments on phytoplankton growth in the northeastern subarctic Pacific. Algae acquire vitamin B 12 through a symbiotic relationship with bacteria. Nature , 90— The distribution of dissolved zinc in the Atlantic sector of the Southern Ocean. II 58 , — Production of extracellular ligands by eucaryotic phytoplankton in response to Cu stress. Thermodynamic characterization of the partitioning of iron between soluble and colloidal species in the Atlantic Ocean. Effects of dissolved carbon dioxide, zinc, and manganese on the cadmium to phosphorus ratio in natural phytoplankton assemblages.

The Biological Chemistry of the Elements. Atmospheric transport of iron and its deposition in the ocean. Ni uptake and limitation in marine Synechococcus strains. Diversity, function and evolution of genes coding for putative Ni-containing superoxide dismutases. Flux comparisons between sediments and sediment traps in the eastern tropical Pacific: implications for atmospheric CO2 variations during the Pleistocene. Zinc and cadmium speciation in subantarctic waters east of New Zealand.

Zinc speciation in the Northeastern Atlantic Ocean. Determination of organic complexation of cobalt in seawater by cathodic stripping voltammetry. Environmental oxidation rate of manganese II : bacterial catalysis. Acta 46 , — Ocean anoxia and the concentration of molybdenum and vanadium in seawater. Evolution of the nitrogen cycle and its influence on the biological sequestration of CO 2 in the ocean. Photochemical and biochemical controls on reactive oxygen and iron speciation in the pelagic surface ocean.

Primary production of the biosphere: integrating terrestrial and oceanic components. Transition metal speciation in the cell: insights from the chemistry of metal ion receptors. Iron and zinc effects on silicic acid and nitrate uptake kinetics in three high-nutrient, low-chlorophyll HNLC regions. The organic complexation of iron in the marine environment: a review. Determination of complexation of iron III with natural organic complexing ligands in seawater using cathodic stripping voltammetry. Effects of cobalt and vitamin B12 on the growth of Crysochromulina polylepis Prymnesiophyceae.

Copper-uptake kinetics of coastal and oceanic diatoms. The effects of iron and copper availability on the copper stoichiometry of marine phytoplankton. Zinc finger proteins as potential targets for toxic metal ions: differential effects on structure and function. Redox Signal. Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean — role in Fe binding, chemical reactivity, and bioavailability. Saccharides enhance iron bioavailability to southern ocean phytoplankton.

The elemental composition of some marine phytoplankton. Interactive influences of iron and light limitation on phytoplankton at subsurface chlorophyll maxima in the eastern North Pacific. Iron transporters in marine prokaryotic genomes.

Nutrition A comprehensive treatise Vol 1 Macro-nutrients and nutrient elements -

The role of siderophores in iron acquisition by photosynthetic marine microorganisms. Biometals 22 , — Iron transport in marine phytoplankton: kinetics of cellular and medium coordination reactions. Which aqueous species control the rates of trace metal uptake by aquatic biota? Observations and predictions of non-equilibrium effects. Total Environ. Trace metal transport by marine microorganisms: implications of metal coordination kinetics.

Iron-binding ligands and their role in the ocean biogeochemistry of iron. Grazer-mediated regeneration and assimilation of Fe, Zn, and Mn from planktonic prey. Iron and regenerated production: evidence for biological iron recycling in two marine environments. Phytoplankton iron limitation in the Humboldt current and Peru upwelling. Competition among marine phytoplankton for different chelated iron speciation. Structure of synechobactins, new siderophores of the marine cyanobacterium Synechococcus sp. PCC T , Evidence for the linked biogeochemical cycling of zinc, cobalt, and phosphorus in the western North Atlantic Ocean.

Global Biogeochem. Cycles 22 , GB Global iron connections between desert dust, ocean biogeochemistry and climate. Science , 67— Cobalt, copper, manganese and nickel in the Sargasso Sea. What controls dissolved iron concentrations in the world ocean? Trace metal reduction by phytoplankton: the role of plasmalemma redox enzymes. The role of reduction in iron uptake processes in a unicellular, planktonic cyanobacterium. Controls on iron III hydroxide solubility in seawater: the influence of pH and natural organic chelators. Sequence analysis and transcriptional regulation of iron acquisition genes in two marine diatoms.

Iron requirements for dinitrogen and ammonium supported growth in cultures of Trichodesmium IMS : comparison with nitrogen fixation rates and iron:carbon ratios of field populations. A revised estimate of the iron use efficiency of nitrogen fixation, with special reference to the marine cynaobacterium trichodesmium spp. Extracellular production of superoxide by marine diatoms: contrasting effects on iron redox chemistry and bioavailabilty. Flavodoxin as an in situ marker for iron stress in phytoplankton.

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  • Nutrition A comprehensive treatise Vol 1 Macro-nutrients and nutrient elements.
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  • Evidence for geochemical control of iron by humic substances in seawater. The contrasting biogeochemistry of iron and manganese in the Pacific Ocean. Acta 51 , 29— The interaction between inorganic iron and cadmium uptake in the marine diatom Thalassiosira oceanica. Effects of iron limitation on intracellular cadmium of cultured phytoplankton: implications for surface dissolved cadmium to phosphate ratios. Regulation of carbonic anhydrase expression by zinc, cobalt, and carbon dioxidein the marine diatom Thalassiosira weissflogii.

    Evidence for strong copper I complexation by organic matter in seawater. Iron and zinc enrichments in the northeastern subarctic Pacific: ligand production and zinc availability in response to phytoplankton growth. Sargasso Sea phosphorus biogeochemistry: an important role for dissolved organic phosphorus DOP. Biogeosciences 7 , — The solubility of iron in seawater. Collection and detection of natural iron-binding ligands from seawater. Copper-dependent iron transport in coastal and oceanic diatoms. Co-limitation of phytoplankton growth by light and Fe during winter in the NE subarctic Pacific Ocean.

    Influence of N substrate on Fe requirements of marine centric diatoms. Reduction and transport of organically bound iron by Thalassiosira oceanica. Aquisition of iron bound to strong organic complexes, with different Fe binding groups and photochemical reactivities, by plankton communities in Fe-limited subantarctic waters. Cycles 19 , GB4S Iron requirements of the pennate diatom Pseudo-nitzschia : comparison of oceanic high-nitrate, low-chlorophyll waters and coastal species. Ferritin is used for iron storage in bloom-forming marine pennate diatoms. Glacial-interglacial CO2 change: the iron hypothesis.

    Paleoceanography 5 , 1— Toronto: D. C Health and Co. Iron deficiency limits phytoplankton growth in the north-east Pacific subarctic. Iron in Antarctic waters. The case for iron. Self-assembling amphiphilic siderophores from marine bacteria. Southern Ocean dust-climate coupling over the past four million years. Hydroxamate siderophores: occurrence and importance in the Atlantic Ocean. Production of siderophore type chelates in Atlantic Ocean waters enriched with different carbon and nitrogen sources.

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    • Seasonal variations in the distribution of Fe and Al in the surface waters of the Arabian Sea. Microbially mediated cerium oxidation in sea water. Temporal and spatial variability of strong copper complexing ligands in the Sargasso Sea. Production of strong, extracellular Cu chelators by marine cyanobacteria in response to Cu stress. Oxidation of cobalt and manganese in seawater via a common microbially catalyzed pathway. Acta 60 , — Measurement of copper I in surface waters of the subtropical Atlantic and Gulf of Mexico.

      Acta 52 , — High rates of N 2 fixation by unicellular diazotrophs in the oligotrophic Pacific Ocean. Upper ocean ecosystem dynamics and iron cycling in a global three-dimensional model. Sedimentary and mineral dust sources of dissolved iron to the world ocean. Biogeoscience 5 , — Iron cycling and nutrient-limitation patterns in surface waters of the World Ocean.

      II 49 , — The role of unchelated Fe in the iron nutrition of phytoplankton. Zinc and carbon co-limitation of marine phytoplankton. Geochemistry of redox sensitive trace metals in sediments. Acta 63 , — Iron enrichment and photoreduction of iron under UVand PAR in the presence of hydroxycarboxylic acid: implications for phytoplankton growth in the Southern Ocean. II 51 , — Potential cobalt limitation of vitamin B12 synthesis in the North Atlantic Ocean.

      Diversity of the cadmium-containing carbonic anhydrase in marine diatoms and natural waters. A role for manganese in superoxide dismutases and growth of iron-deficient diatoms. Copper-containing plastocyanin used for electron transport by an oceanic diatom. Copper requirements for iron acquisition and growth of coastal and oceanic diatoms. Viral release of iron and its bioavailability to marine plankton. The equatorial Pacific Ocean: grazer-controlled phytoplancton population in an iron-limited ecosystem.

      Iron and nitrogen nutrition of equitorial Pacific plankton. Cadmium and cobalt substitution for zinc in a marine diatom. Colimitation of phytoplankton growth by nickel and nitrogen. The iron and molybdenum use efficiences of plant growth with different energy, carbon and nitrogen sources. New Phytol. Predictions of Mn and Fe use efficiencies of phototrophic growth as a function of light availability for growth and C assimilation pathway.

      The role of trace metals in photosynthetic electron transport in O2-evolving organisms. Hill M. Use of superoxide as an electron shuttle for iron acquisition by the marine cyanobacterium Lyngbya majuscula. Persistence of iron II in surface waters of the western subarctic Pacific. Dust- and mineral-iron utilization by the marine dinitrogen-fixer Trichodesmium.

      Domoic acid binds iron and copper: a possible role for the toxin produced by the marine diatom Pseudo-nitzschia. Complexation of iron III by natural organic-ligands in the central north pacific as determined by a new competitive ligand equilibration adsorptive cathodic stripping voltammetric method. Theoretical iron limitation of microbial N 2 fixation in the oceans. Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii. Zinc-cobalt colimitation of Phaeocystis antarctica. This book has hardback covers.

      In good all round condition. No dust jacket. Please note the Image in this listing is a stock photo and may not match the covers of the actual item,grams, ISBN: Seller Inventory More information about this seller Contact this seller 2. Published by Academic Press , London About this Item: Academic Press , London, Condition: Very Good. Seller Inventory PAB More information about this seller Contact this seller 3.

      Hardbound Clothbinding. No Jacket. For individual volumes, please enquire. Solidly bound copy with minimal external wear, crisp pages and clean text. No dj.