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The New Carbohydrate Intake Recommendations
Abstract
Carbohydrate intake during prolonged exercise has been shown to increase endurance capacity and improve performance. Until recently, the advice was to ingest 30-60 g of carbohydrate per hour. The upper limit was based on studies that demonstrated that intakes greater than 60-70 g/h would not result in greater exogenous carbohydrate oxidation rates. The lower limit was an estimated guess of the minimum amount of carbohydrate required for ergogenic effects. In addition, the advice was independent of the type, the duration or the intensity of the activity as well as the level of athlete. Since 2004, significant advances in the understanding of the effects of carbohydrate intake during exercise have made it possible to be much more prescriptive and individual with the advice. Studies revealed that oxidation rates can reach much higher values (up to 105 g/h) when multiple transportable carbohydrates are ingested (i.e. glucose:fructose). It has also been observed that carbohydrate ingested during shorter higher intensity exercise (1 h, 80%VO2max) can improve performance, although mechanisms are distinctly different. These findings resulted in new recommendations that are dependent on the duration and intensity of exercise and not only specify the quantity of carbohydrate to be ingested but also the type. Copyright © 2013 Nestec Ltd., Vevey/S. Karger AG, Basel.
... Portion sizes were verified based on the "Album of photographs of food products and dishes" (published by the Polish Institute of Food and Nutrition, Warsaw, Poland) [21]. In the evaluation of the three-day dietary diaries provided by the participants, daily energy intake, content of the main nutrients, vitamins, minerals, cholesterol and dietary fiber were taken into consideration, and the results were compared with the findings of studies on longdistance running [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Data obtained from daily food rations were analyzed using a computer program "Dieta 5" (developed by the National Institute of Public Health, Warsaw, Poland). ...
... Portion sizes were verified based on the "Album of photographs of food products and dishes" (published by the Polish Institute of Food and Nutrition, Warsaw, Poland) [21]. In the evaluation of the three-day dietary diaries provided by the participants, daily energy intake, content of the main nutrients, vitamins, minerals, cholesterol and dietary fiber were taken into consideration, and the results were compared with the findings of studies on long-distance running [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Data obtained from daily food rations were analyzed using a computer program "Dieta 5" (developed by the National Institute of Public Health, Warsaw, Poland). ...
As many as 70% of athletes who practice endurance sports report experiencing gastrointestinal (GI) symptoms, such as abdominal pain, intestinal gurgling or splashing (borborygmus), diarrhea or the presence of blood in the stool, that occur during or after intense physical exercise. The aim of the study was to evaluate the effect of a multi-strain probiotic on the incidence of gastrointestinal symptoms and selected biochemical parameters in the serum of long-distance runners. After a 3-month intervention with a multi-strain probiotic, a high percentage of runners reported subjective improvement in their general health. Moreover, a lower incidence of constipation was observed. In the group of women using the probiotic, a statistically significant (p = 0.035) increase in serum HDL cholesterol concentration and a favorable lower concentration of LDL cholesterol and triglycerides were observed. These changes were not observed in the group of men using the probiotic. Probiotic therapy may reduce the incidence and severity of selected gastrointestinal symptoms in long-distance runners and improve subjectively assessed health condition.
... Although the benefits of carbohydrate ingestion during exercise are generally recognized [38][39][40][41], carbohydrate supplementation during exercise may not have only positive effects. The positive effects may refer to the acute situation, but it has been suggested that chronic use of carbohydrate during exercise may limit training adaptations. ...
... The second reason for training high is related to intestinal function. In longer events, it is clear that ingesting carbohydrates and increasing exogenous carbohydrate oxidation will result in improved endurance performance in most events [38][39][40][41]68]. The effects of training high on intestinal function has been discussed in detail in a separate review article in this Sports Medicine Supplement issue [15]. ...
It is becoming increasingly clear that adaptations, initiated by exercise, can be amplified or reduced by nutrition. Various methods have been discussed to optimize training adaptations and some of these methods have been subject to extensive study. To date, most methods have focused on skeletal muscle, but it is important to note that training effects also include adaptations in other tissues (e.g., brain, vasculature), improvements in the absorptive capacity of the intestine, increases in tolerance to dehydration, and other effects that have received less attention in the literature. The purpose of this review is to define the concept of periodized nutrition (also referred to as nutritional training) and summarize the wide variety of methods available to athletes. The reader is referred to several other recent review articles that have discussed aspects of periodized nutrition in much more detail with primarily a focus on adaptations in the muscle. The purpose of this review is not to discuss the literature in great detail but to clearly define the concept and to give a complete overview of the methods available, with an emphasis on adaptations that are not in the muscle. Whilst there is good evidence for some methods, other proposed methods are mere theories that remain to be tested. ‘Periodized nutrition’ refers to the strategic combined use of exercise training and nutrition, or nutrition only, with the overall aim to obtain adaptations that support exercise performance. The term nutritional training is sometimes used to describe the same methods and these terms can be used interchangeably. In this review, an overview is given of some of the most common methods of periodized nutrition including ‘training low’ and ‘training high’, and training with low- and high-carbohydrate availability, respectively. ‘Training low’ in particular has received considerable attention and several variations of ‘train low’ have been proposed. ‘Training-low’ studies have generally shown beneficial effects in terms of signaling and transcription, but to date, few studies have been able to show any effects on performance. In addition to ‘train low’ and ‘train high’, methods have been developed to ‘train the gut’, train hypohydrated (to reduce the negative effects of dehydration), and train with various supplements that may increase the training adaptations longer term. Which of these methods should be used depends on the specific goals of the individual and there is no method (or diet) that will address all needs of an individual in all situations. Therefore, appropriate practical application lies in the optimal combination of different nutritional training methods. Some of these methods have already found their way into training practices of athletes, even though evidence for their efficacy is sometimes scarce at best. Many pragmatic questions remain unanswered and another goal of this review is to identify some of the remaining questions that may have great practical relevance and should be the focus of future research.
... • Ağır antrenmanlarda bağırsakla ilgili fonksiyonlar önemlidir. Uzun süreli egzersizlerde CHO sindirimi ve exogenous CHO oksidasyonun artması dayanıklılık performansını gelişmesiyle sonuçlanır (Jeukendrup, 2013). ...
... CHO intake has been shown to delay the onset of fatigue and improve endurance capacity (11)(12)(13). Current recommendations (1,(14)(15)(16) suggest that athletes consume large amounts of CHO before and during prolonged exercise to optimize performance. For example, the recommended CHO intake is more than 30 to 60 g/h. ...
The present guidelines for sports nutrition recommend relatively higher doses of carbohydrates (CHO) for endurance exercise. There is a need for novel food products that are solid but easy to swallow and supply a large dose of CHO without gastrointestinal distress (ingesting a large amount of sugar solution may cause gastrointestinal distress because of its high osmolality). We prepared a modified rice cake (SPRC, sweet potato rice cake) and assessed its properties in swallowing and mastication; we also assessed the availability of this modified rice cake as a CHO source during endurance exercise. The number of chewing strokes with the SPRC tended to be lower compared to glutinous rice cakes. The exercise protocol consisted of 1 h at 80% VO2max plus a continuous time trial. The subjects were administered a commercially available jelly drink (CHO gel) or SPRC at 0 and 30 min during exercise and immediately after completing the time trial. Heart rate, oxygen consumption, blood glucose elevation, and the rate of perceived exertion did not differ among the trials during exercise. However, the visual analog scale rating revealed that SPRC significantly suppressed hunger and sweetness ratings (p<0.05) and tended to suppress thirst ratings (p<0.10) during exercise. The palatability rating did not differ between the SPRC and CHO gel during exercise at 80% VO2max and immediately after the time trial. In conclusion, pre- and during exercise ingestion of the SPRC suppressed sweetness, thirst, and hungry ratings without interfering with exercise performance.
... Ingesting carbohydrate in any of these forms allows the athlete to go harder longer as the provision of carbohydrate decreases the use of stored glycogen. [72][73][74][75][76][77][78] A rate of ≈30 to 60 grams/hour will maintain blood glucose 79,80 and are recommended for exercise lasting more than an hour. 73,[81][82][83][84][85] While sports beverages provide the allure of rehydrating as well as a source of carbohydrate, athletes are warned against products that have a carbohydrate concentration greater than 7% as they reduce gastric emptying, the anatomic limiting step to rehydration efforts. ...
With the continued increase in international travel and immigration to Georgia, the Department of Public Health (DPH) continued its mission to prevent and respond to Zika virus (ZIKV) transmission.
Methods:
We analyzed surveillance data from the DPH to compare the geographical distribution of counties conducting surveillance, total number, and overall percentage of mosquito species collected in 2016 and 2017. Mosquito surveillance in 2017 was mapped by county and species using ArcMap 10.2.0.
Results:
From 2016 and 2017, mosquito surveillance increased from 60 to 159 counties (165% increase). A total of 145,346 mosquitoes were trapped and identified in 2016 compared to 152,593 in 2017 (5.43% increase). There was a difference in the type of mosquito species found by year. Some species collected in previous years were not collected in 2017, while other species found in 2017 were not previously collected during mosquito surveillance. Also, certain mosquito species were found outside of their expected geographical range.
Conclusion:
The continued collaborative response to ZIKV by the DPH allowed a continued increase in its surveillance program. Existing and new partnerships continued to develop with military and local health departments to expand and share data. This additional surveillance data allowed DPH to make sound public health decisions regarding mosquito-borne disease risks and close gaps in data related to vector distribution.
... 34,52 A fat-burning adapted Ironman triathlete is able to use the fat stores in his or her body to fuel the race effectively at that oxidation rate for the entire race compared with a carbohydrateburning athlete who would need to consume another 90 to 105 g per hour to maintain performance. 5,14 Studies addressing the effects of low-carbohydrate diets on the ease of weight control in athletes, the capacity to train and recover, immune function and injury risk, or hand-eye coordination or capacity to concentrate in sports are lacking. 29 Additionally, some endurance athletes can be insulin resistant, and eating a diet high in carbohydrates may not be best for their long-term health. ...
Context:
Proper nutrition is crucial for an athlete to optimize his or her performance for training and competition. Athletes should be able to meet their dietary needs through eating a wide variety of whole food sources.
Evidence acquisition:
PubMed was searched for relevant articles published from 1980 to 2016.
Study design:
Clinical review.
Level of evidence:
Level 4.
Results:
An athlete should have both daily and activity-specific goals for obtaining the fuel necessary for successful training. Depending on the timing of their season, athletes may be either trying to gain lean muscle mass, lose fat, or maintain their current weight.
Conclusion:
An athlete will have different macronutrient goals depending on sport, timing of exercise, and season status. There are no specific athletic micronutrient guidelines, but testing should be considered for athletes with deficiency or injury. Also, some athletes who eliminate certain whole food groups (eg, vegetarian) may need to supplement their diet to avoid deficiencies.
Carbohydrate ingestion can improve endurance capacity and performance. Since the 1980s, research has focused on optimizing the delivery strategies of these carbohydrates. The optimal dose of carbohydrate is still subject to debate, but recent evidence suggests that there may be a dose–response effect as long as the carbohydrate ingested is also oxidized and does not result in gastrointestinal distress. Oxidation rates of a single type of carbohydrate do not exceed 60 g·h−1. However, when multiple transportable carbohydrates are ingested (i.e. glucose and fructose), these oxidation rates can be increased significantly (up to 105 g·h−1). To achieve these high oxidation rates, carbohydrate needs to be ingested at high rates and this has often been associated with poor fluid delivery as well as gastrointestinal distress. However, it has been suggested that using multiple transportable carbohydrates may enhance fluid delivery compared with a single carbohydrate and may cause relatively little gastrointestinal distress. More research is needed to investigate the practical applications of some of the recent findings discussed in this review.
When ingested at high rates (1.8-2.4 g·min(-1)) in concentrated solutions, carbohydrates absorbed by multiple (e.g., fructose and glucose) vs. single intestinal transporters can increase exogenous carbohydrate oxidation and endurance performance, but their effect when ingested at lower, more realistic, rates during intermittent high-intensity endurance competition and trials is unknown. Trained cyclists participated in two independent randomized crossover investigations comprising mountain-bike races (average 141 min; n = 10) and laboratory trials (94-min high-intensity intervals followed by 10 maximal sprints; n = 16). Solutions ingested during exercise contained electrolytes and fructose + maltodextrin or glucose + maltodextrin in 1:2 ratio ingested, on average, at 1.2 g carbohydrate·kg(-1)·h(-1). Exertion, muscle fatigue, and gastrointestinal discomfort were recorded. Data were analysed using mixed models with gastrointestinal discomfort as a mechanism covariate; inferences were made against substantiveness thresholds (1.2% for performance) and standardized difference. The fructose-maltodextrin solution substantially reduced race time (-1.8%; 90% confidence interval = ±1.8%) and abdominal cramps (-8.1 on a 0-100 scale; ±6.6). After accounting for gastrointestinal discomfort, the effect of the fructose-maltodextrin solution on lap time was reduced (-1.1%; ±2.4%), suggesting that gastrointestinal discomfort explained part of the effect of fructose-maltodextrin on performance. In the laboratory, mean sprint power was enhanced (1.4%; ±0.8%) with fructose-maltodextrin, but the effect on peak power was unclear (0.7%; ±1.5%). Adjusting out gastrointestinal discomfort augmented the fructose-maltodextrin effect on mean (2.6%; ±1.9%) and peak (2.5%; ±3.0%) power. Ingestion of multiple transportable vs. single transportable carbohydrates enhanced mountain-bike race and high-intensity laboratory cycling performance, with inconsistent but not irreconcilable effects of gut discomfort as a possible mediating mechanism.
Background. Oropharyngeal receptors signal presence of carbohydrate to the brain. Mouth rinses with a carbohydrate solution facilitate corticomotor output and improve time-trial performance in well-trained subjects in a fasted state. We tested for this effect in nonathletic subjects in fasted and nonfasted state.
Methods. 13 healthy non-athletic males performed 5 tests on a cycle ergometer. After measuring maximum power output (Wmax), the subjects cycled four times at 60% Wmax until exhaustion while rinsing their mouth every 5 minutes with either a 6.4% maltodextrin solution or water, one time after an overnight fast and another after a carbohydrate rich breakfast.
Results. Mouth rinsing with maltodextrin improved time-to-exhaustion in pre- and postprandial states. This was accompanied by reductions in the average and maximal rates of perceived exertion but no change in average or maximal heart rate was observed.
Conclusions. Carbohydrate mouth rinsing improves endurance capacity in both fed and fasted states in non-athletic subjects.
We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group; n = 8) or an energy-matched low-carbohydrate group (Low group; n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 micromol x g(-1) x min(-1), P < 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g (P < 0.01) in the High group with no change in the Low group. Cycling performance improved by approximately 6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance.
Exercise studies have suggested that the presence of carbohydrate in the human mouth activates regions of the brain that can enhance exercise performance but direct evidence of such a mechanism is limited. The first aim of the present study was to observe how rinsing the mouth with solutions containing glucose and maltodextrin, disguised with artificial sweetener, would affect exercise performance. The second aim was to use functional magnetic resonance imaging (fMRI) to identify the brain regions activated by these substances. In Study 1A, eight endurance-trained cyclists ( 60.8 ± 4.1 ml kg−1 min−1) completed a cycle time trial (total work = 914 ± 29 kJ) significantly faster when rinsing their mouths with a 6.4% glucose solution compared with a placebo containing saccharin (60.4 ± 3.7 and 61.6 ± 3.8 min, respectively, P= 0.007). The corresponding fMRI study (Study 1B) revealed that oral exposure to glucose activated reward-related brain regions, including the anterior cingulate cortex and striatum, which were unresponsive to saccharin. In Study 2A, eight endurance-trained cyclists ( 57.8 ± 3.2 ml kg−1 min−1) tested the effect of rinsing with a 6.4% maltodextrin solution on exercise performance, showing it to significantly reduce the time to complete the cycle time trial (total work = 837 ± 68 kJ) compared to an artificially sweetened placebo (62.6 ± 4.7 and 64.6 ± 4.9 min, respectively, P= 0.012). The second neuroimaging study (Study 2B) compared the cortical response to oral maltodextrin and glucose, revealing a similar pattern of brain activation in response to the two carbohydrate solutions, including areas of the insula/frontal operculum, orbitofrontal cortex and striatum. The results suggest that the improvement in exercise performance that is observed when carbohydrate is present in the mouth may be due to the activation of brain regions believed to be involved in reward and motor control. The findings also suggest that there may be a class of so far unidentified oral receptors that respond to carbohydrate independently of those for sweetness.
Carbohydrate feeding has been shown to enhance endurance performance. During exercise of 2 h or more, the delivery of carbohydrates to the muscle is the crucial step and appears to be limited by intestinal absorption. It is therefore important to identify ways to overcome this limitation and study the positive and negative effects of chronic carbohydrate supplementation. There is evidence that intestinal absorption can, at least partly, be overcome by making use of multiple transportable carbohydrates. Ingestion of these carbohydrates may result in higher intestinal absorption rates and has been shown to lead to higher rates of exogenous carbohydrate oxidation which can result in better endurance performance. It also seems possible to increase the absorptive capacity of the intestine by adapting to a high-carbohydrate diet. Carbohydrate supplementation during exercise has been suggested to reduce training adaptations, but at present there is little or no evidence to support this. Despite the fact that it has long been known that carbohydrate supplementation can enhance endurance performance, there are still many unanswered questions. However, there is potential to develop strategies that enhance the delivery of carbohydrates and thereby improve endurance performance.
# DON'T FORGET THE GUT—IT IS AN IMPORTANT ATHLETIC ORGAN! {#article-title-2}
to the editor: It was with great interest that we read the Journal of Applied Physiology Viewpoint on the 2-h marathon barrier ([3][1]). We would argue that, alongside having a superlative V̇o2max, lactate threshold,
Carbohydrate feeding has been shown to be ergogenic, but recently substantial advances have been made in optimizing the guidelines for carbohydrate intake during prolonged exercise.
It was found that limitations to carbohydrate oxidation were in the absorptive process most likely because of a saturation of carbohydrate transporters. By using a combination of carbohydrates that use different intestinal transporters for absorption it was shown that carbohydrate delivery and oxidation could be increased. Studies demonstrated increases in exogenous carbohydrate oxidation rates of up to 65% of glucose: fructose compared with glucose only. Exogenous carbohydrate oxidation rates reach values of 1.75 g/min whereas previously it was thought that 1 g/min was the absolute maximum. The increased carbohydrate oxidation with multiple transportable carbohydrates was accompanied by increased fluid delivery and improved oxidation efficiency, and thus the likelihood of gastrointestinal distress may be diminished. Studies also demonstrated reduced fatigue and improved exercise performance with multiple transportable carbohydrates compared with a single carbohydrate.
Multiple transportable carbohydrates, ingested at high rates, can be beneficial during endurance sports in which the duration of exercise is 3 h or more.
Carbohydrate during exercise has been demonstrated to improve exercise performance even when the exercise is of high intensity (>75% VO2max) and relatively short duration (approximately 1 h). It has become clear that the underlying mechanisms for the ergogenic effect during this type of activity are not metabolic but may reside in the central nervous system.
Carbohydrate mouth rinses have been shown to result in similar performance improvements. This would suggest that the beneficial effects of carbohydrate feeding during exercise are not confined to its conventional metabolic advantage but may also serve as a positive afferent signal capable of modifying motor output. These effects are specific to carbohydrate and are independent of taste. The receptors in the oral cavity have not (yet) been identified and the exact role of various brain areas is not clearly understood. Further research is warranted to fully understand the separate taste transduction pathways for simple and complex carbohydrates and how these differ between mammalian species, particularly in humans.
Carbohydrate is detected in oral cavity by unidentified receptors and this can be linked to improvements in exercise performance.
Recently, it has been shown that ingestion of solutions with glucose (GLU) and fructose (FRC) leads to 20%–50% higher CHO oxidation rates compared with GLU alone. Although most laboratory studies used solutions to deliver CHO, in practice, athletes often ingest CHO in the form of gels (semisolid). It is currently not known if CHO ingested in the form of a gel is oxidized as effectively as a drink.
To investigate exogenous CHO oxidation from CHO provided in semisolid (GEL) or solution (DRINK) form during cycling.
Eight well-trained cyclists(age = 34 ± 7 yr, mass = 76 ± 9 kg, VO2max = 61 ± 7 mL·kg−¹·min−¹) performed three exercise trials in random order. The trials consisted of cycling at 59% ± 4% VO2max for 180 min while receiving one of the following three treatments: GEL plus plain water, DRINK, or plain water. Both CHO treatments delivered GLU plus FRC in a ratio of 2:1 at a rate of 1.8 g·min−¹ (108 g·h−¹). Fluid intake was matched between treatments at 867 mL·h−¹.
Exogenous CHO oxidation from GEL and DRINK showed a similar time course,with peak exogenous CHO oxidation rates being reached at the end of the 180-min exercise. Peak exogenous CHO oxidation rates were not significantly different (P = 0.40) between GEL and DRINK (1.44 ± 0.29 vs 1.42 ± 0.23 g·min−¹, respectively). Furthermore, oxidation efficiency was not significantly different (P = 0.36) between GEL and DRINK (71% ± 15% vs 69% ± 13%, respectively).
This study demonstrates that a GLU + FRC mixture is oxidized to the same degree then administered as either semisolid GEL or liquid DRINK, leading to similarly high peak oxidation rates and oxidation efficiencies.