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FA CT S H E ET Sugar in the diet of sports people The right diet is as important as the right amount of training for all sports people. There are benefits to be gained from paying attention to food and fluid intake, for both the serious athlete and those who participate in casual exercise. Diet and nutrition could significantly improve progress, performance and enjoyment during training and competition. Correct nutrition could also reduce the risk of injuries, fatigue and susceptibility to illness. Dietary carbohydrates provide the major energy source in the diet of most people. For sports people, attention to both the quantity and quality of the carbohydrate in the diet can be particularly important. Carbohydrates are provided by a diverse range of foods and drinks and there is no universal system that can adequately describe the diverse metabolic, functional and nutritional features of these various carbohydrate containing foods. Athletes are encouraged by peak sports and nutrition organisations to choose carbohydrate-rich foods and drinks that meet their specific needs in regards to nutrient-density, glycaemic index, eating appeal and practicality according to the requirements of each sporting situation.1 This fact sheet provides an overview of the role of sugars in the diet of sports people. The dietary needs of individuals vary enormously and this is particularly so with sportspeople. The food and nutrition requirements of an endurance athlete who runs marathons will be quite different to the needs of someone who plays a high intensity sport, such as rugby. If you are very serious about your sport, or are simply feeling that you don’t have the energy you need to really enjoy it, you could benefit from one-to-one advice from a qualified health professional such as a sports dietitian. However, there are some basic principles that could apply to everyone and these principles are outlined in this fact sheet. This information summarises recommendations from peak sports and nutrition organisations. For more information you may wish to contact these organisations directly; Australian Institute of Sport (www.ais.org.au), High Performance Sport New Zealand (www.hpsnz.org.nz), Dietitians Association of Australia (www.daa.asn.au) and Dietitians New Zealand (www.dietitians.org.nz). Where does sugar fit in the diet? Carbohydrates, including sugars, are a fuel source for the muscles and central nervous system.2 The availability of carbohydrate can play a key role in exercise performance, therefore, many sports nutrition guidelines promote carbohydrate intake before, sometimes during and after exercise to meet the fuel requirements of the activity.2, 3 CONTINUED OVER ACUTE FUELLING STRATEGIES DAILY NEEDS FOR FUEL AND RECOVERY TABLE 1: RECOMMENDED CARBOHYDRATE INTAKES2 SITUATION RECOMMENDED CARBOHYDRATE INTAKE Low-intensity or skill-based activities 3-5 g/kg body weight Moderate exercise for ~1 hr/day 5-7 g/kg body weight Moderate to high intensity exercise for 1-3 hrs/day 6-10 g/kg body weight Moderate to high intensity exercise for >4-5 hrs/day 8-12 g/kg body weight Preparation for events <1.5 hrs 7-12 g/kg body weight per 24 hrs (as per daily fuel needs) Carbohydrate loading in preparation for events >1.5 hrs of sustained/intermittent exercise 1-4 g/kg body weight (consumed 1-4 hrs pre-competition) During brief exercise (<45 min) Not required During sustained high-intensity exercise (45-75 min) Small amounts including mouth rinse During endurance exercise including “stop and start” sports (1-2.5 hrs) 30-60 g/hr During ultra-endurance exercise (2.5-3 hrs) Up to 90 g/hr using multiple transportable carbohydrates (glucose: fructose mix) Speedy refuelling when there is <8 hrs recovery between two fuel demanding sessions 1-1.2 g/kg body weight every hr for first 4 hrs then resume daily fuel needs 1 FA CT S H E ET CONTINUED Where does sugar fit in the diet? Carbohydrates can be broadly categorised into sugars, starches and dietary fibre, all of which are dealt with quite differently by the body.4 An athlete with inadequate carbohydrate intake or stores may suffer from fatigue, reduced ability to train hard, impaired cognitive performance, and a reduction in immune system function. Hence, athletes who train for longer than 45 minutes may require higher carbohydrate intakes than the general population.2 An athlete’s individual carbohydrate requirements are dependent on the fuel needs of their training and competition programme, but Table 1, provides general targets from the Australian Institute of Sport.2 Before exercise: Building energy stores for the event Excess glucose is stored in the muscles as glycogen. The amount of glycogen in the muscles at the start of exercise is seen to be proportional to the amount of time an athlete can perform before exhaustion or fatigue sets in. Carbohydrate loading for endurance athletes is a strategy used to increase muscle glycogen stores. It involves changes to training and nutrition patterns one to four days before an endurance event. The Australian Institute of Sport suggests that carbohydrate loading is appropriate for anyone exercising for 90 minutes or longer, for example marathon runners or triathletes.5 Carbohydrate loading enables the muscle glycogen levels to be increased from the normal range of 100-120mmol/kg ww (wet weight) to around 150-200mmol/kg ww. In the past carbohydrate loading was preceded by a period of carbohydrate depletion. However, now the experts recommend exercise taper combined with a high carbohydrate diet (7-12 g/kg body weight) one to four days prior to the event to elevate muscle glycogen levels.5 The extra supply of carbohydrate can help improve performance over a set distance by 2-3% allowing the athlete to exercise for a longer period of time.5 When carbohydrate loading it is suggested to stick to high-carbohydrate, low-fat foods as it can help athletes meet the higher carbohydrate requirements during this time. It is also helpful to cut back on fibre and make use of compact, readily digestible sources of carbohydrate such as sugar, cordial, soft drink, sports drink, jam, honey, jelly and tinned fruit. Athletes who include too many high fibre foods in their carbohydrate loading menu may suffer gastro-intestinal discomfort or find the food too bulky to consume. Consuming too many high fat foods will also make it difficult to consume sufficient carbohydrate.5 A general guide is to have a meal about 3-4 hours before exercise or a lighter snack 1-2 hours before exercise. It has been suggested that low GI foods could be useful in the pre-event meal as they would result in a slower and more sustained release of glucose during exercise, maintaining blood glucose levels for a longer period. However, consuming low GI foods prior to exercise has not been associated with universal benefits on exercise performance. Consuming carbohydrate (e.g. sports drink) during exercise can provide an alternative way to maintain fuel levels throughout the activity and this practice may override the effects of different types of carbohydrate in the pre-event meal. Athletes wishing to achieve optimum results should also consider working with a sports dietitian who can prepare a carb-loading plan to individual needs. During exercise: Getting the most from the event Performance and enjoyment of an event will be enhanced if the athlete has the right fuel on board. The appropriate carbohydrate food or drink to consume generally depends on the athlete’s previous experience, the type of event, gastrointestinal comfort and the need for fluid replacement. If the event duration is greater than 45 minutes then carbohydrate intake during the event may be beneficial (Table 1 provides some general targets). While the GI of foods consumed during exercise has not been thoroughly studied, athletes typically choose moderate to high GI carbohydrate sources, such as specifically developed sports drinks or sports gels. The optimum source and concentration of carbohydrate will depend on individual circumstances, so trialing different types of sports drinks and foods prior to competing is suggested as this can help determine which products work for you. The ingestion of glucose during prolonged intense exercise can prevent the development of hypoglycaemia (low blood glucose) by maintaining or raising the circulating glucose concentration.6 As a result, an improvement in performance is consistently observed with the provision of additional fuel during prolonged moderate intensity or intermittent high-intensity exercise.7 Adequate hydration is also very important. When exercising or participating in an event for longer than 30 minutes, fluid top ups are needed. Water is sufficient for many athletes but if the duration of the event or training is longer than an hour then individuals may benefit from consuming sports drinks.7 Sports drinks can be an efficient option during an event as they provide carbohydrate and fluid. Sports drinks use glucose, glucose polymers, sucrose and fructose as a carbohydrate source, with a total carbohydrate concentration of 4-8% (4-8 g/100mL). Most sports drinks also contain sodium (typically 10-30mmol/L), which is an electrolyte replacement and also aids in the absorption of sugar.7 A specially formulated sports drink is likely to be more effective than a standard juice or soft drink.7 2 FACT SH E ET After exercise: Rebuilding energy stores after the event Refueling after exercise or an event is as important as before and during activity. Recovery from exercise is not a passive process. Tissues undergo repair and reproduction, fluid balance is restored and glycogen stores are replaced. Carbohydrate replacement is one of the most important strategies as the muscle enzymes are receptive to glucose. There is a direct and positive relationship between the quantity of carbohydrate consumed and post-exercise glycogen storage.8 It appears that high GI foods achieve better post-exercise glycogen storage.9 Examples of high GI foods that could be eaten after an event include; sports drinks, some breakfast cereals, jam sandwiches and jellybeans. Not replenishing energy stores may result in low muscle stores, which could lead to early fatigue and poor sports ongoing performance. Injuries and the onset of illness can affect athletes who have low glycogen levels and can occur from 3-72 hours after prolonged exercise (greater than 90 minutes) when immune function may be reduced. To protect against this, having carbohydrate drinks (60g carbohydrate per hour) before, during and after exercise have been shown to raise plasma glucose levels.10 For athletes who have several competitions in a row, it is suggested that carbohydrate replacement should be a priority. The source and spacing of carbohydrates is important to reduce the likelihood of gastrointestinal upsets when competing. Between competitions athletes may find avoiding high fibre and high fat foods helpful, instead opting for white breads, rice, low fibre cereals or a liquid meal. Types of carbohydrates The digestion of carbohydrates is useful for athletes to understand. The digestion process breaks down carbohydrates into glucose, which provides energy to our body, commonly called blood glucose. Excess glucose is stored in the muscles as glycogen, which is used by exercising muscles. The speed of the breakdown of carbohydrate foods into glucose and its subsequent effect on raising blood glucose varies greatly between individuals and is mainly dependent on the overall composition of the food. For example a slice of bread may contain dietary fibre, wheat starch and a small amount of sugar. The breakdown of all these carbohydrate components is interlinked. Sugars and starches Total sugars include monosaccharides, disaccharides, polysaccharides (starches) and polyols.4 All go through a complicated digestion process to ultimately produce glucose. Sugars include glucose, fructose, lactose, maltose and sucrose (table sugar). Sugars are the least complicated of carbohydrates, meaning they are easily digested and absorbed. Hence, an athlete who wants a quick burst of energy during an event might consume a sugary food such as lollies. But if an athlete needs energy over a more extended time period consuming sugar as part of a mixed meal may slow the digestion of the carbohydrate to give a more steady flow of energy. Carbohydrate quality Many foods and drinks contain carbohydrates. When it comes to choosing what sources of carbohydrate an athlete should use it is not as simple as just looking at the total carbohydrate content, or even considering carbohydrate type. High quality carbohydrate foods are generally nutrient-dense, meaning that there are other beneficial nutrients in addition to carbohydrate, and these should be the primary source of carbohydrate in all athletes’ diets.2 Nutrient-poor carbohydrate foods may be beneficial occasionally by providing a compact and readily digestible carbohydrate source around training. From a sports nutrition point of view, the Australian Institute of Sport categorizes carbohydrates as nutrient-dense, nutrient-poor or high-fat, and provides recommendations for how these separate groups should fit into an athlete’s diet (Table 2).2 Dietary fibre Dietary fibre is described as being resistant to digestion and absorption in the small intestine.4 However; this can be misleading as some dietary fibre is digested. This takes place in the large intestine rather than in the stomach by normal digestive processes. These carbohydrates move through the body’s system relatively unchanged. Dietary fibre confers many benefits including slowing the release of energy from foods, stabilising blood glucose levels, as well as keeping our digestive tract healthy. Sugars and starches are found in carbohydrate-rich foods such as breads, cereals, pastas, fruits and vegetables as well as many pre-prepared and ready to eat meals and beverages. 3 FA CT S H E ET TABLE 2: CARBOHYDRATE CATEGORIES FROM A SPORTS NUTRITION PERSPECTIVE2 CATEGORY DESCRIPTION EXAMPLES USE FOR ATHLETES Nutrient-dense carbohydrate Foods and drinks that are rich sources of other nutrients including protein vitamins, minerals, fibre and antioxidants in addition to carbohydrate Breads and cereals grains (e.g. pasta, rice), fruit starchy vegetables (e.g. potato, corn) legumes and low-fat dairy products Everyday food that should form the base of an athlete’s diet. Helps to meet other nutrient targets Nutrient-poor carbohydrate Foods and drinks that contain carbohydrate but minimal or no other nutrients Soft drinks, energy drinks lollies, carbohydrate gels sports drink and cordial Shouldn’t be a major part of the everyday diet but may provide a compact carbohydrate source around training High-fat carbohydrate Foods that contain carbohydrate but are high in fat Pastries, cakes, chips (hot and crisps) and chocolate ‘Sometimes’ foods best not consumed around training sessions The Glycaemic Index (GI) is another tool for athletes to work out what food suits them best for their sport and personal choice. Glycaemic Index is a ranking of how quickly carbohydrate foods raise blood glucose levels in the body following ingestion. Athletes who need a quick release of energy from their food could benefit from consuming high GI foods, while those who need a sustained release of food energy, such as endurance athletes, may benefit from consuming low GI foods.2 Refer to the Glycaemic Index website for more information (www.glycemicindex.com). Conclusion A balanced diet made up of a variety of foods can make a real difference to a sports person’s performance and exercise enjoyment. An integral and valuable part of such a diet is carbohydrate, which can include sugars. Last updated August 2014 REFERENCES 1. Burke, L M. Dietary carbohydrates. In: The Encyclopaedia of Sports Medicine. Vol VII Nutrition in Sport, edited by R.J. Maughan. Oxford: Blackwell Science, 2000, p.73-84. Sourced from http://www.ausport.gov.au/ais/nutrition/research/overview) 2. Australian Institute of Sport. Sports Nutrition 2014 Fact Sheet: Carbohydrate- the facts. Available at: http://www.ausport.gov.au/ais/nutrition/factsheets/basics/carbohydrate__how_much 3. Millennium Institute of Sport & Health & Nestle New Zealand, 2009. Carbohydrate and sports performance. Available at: http://www.autmillennium.org.nz/wpcontent/uploads/2013/01/CARBOHYDRATE.pdf 4. Cummings JH and Stephen AM. Carbohydrates terminology and classification. FAO/WHO scientific update on carbohydrates in human nutrition. Eur J Clin Nutr. Dec 2007;61 Suppl 1:S5-18 5. Australian Institute of Sport. Sports Nutrition 2009 Fact Sheet: Carbohydrate loading. Available at: http://www.ausport.gov.au/ais/nutrition/factsheets/competition_and_training/carbohydrate_loading 6. Wilmore, J.H. & Costill, DL. (1994) Physiology of Sport end Exercise, Human Kinetics, USA 7. Australian Institute of Sport. Sports Nutrition 2009 Fact sheet: Fluid- who needs it? Available at: http://www.ausport.gov.au/ais/nutrition/factsheets/hydration/fluid_-_who_needs_it 8. Burke LM, Kiens B, Ivy JL. Carbohydrates and fat for training and recovery. J Sports Sci. 2004;22(1):15-30. 9. Burke & Deakin (2007). Clinical Sports Nutrition. 3rd edition. McGraw-Hill, Sydney The Sugar Research Advisory Service (SRAS) is a scientific information service, advised by a panel of independent health and nutrition experts. To contact SRAS and for further information please go to www.SRASANZ.org Contact details are: The Secretariat SRAS PO Box 5224 Wellesley Street Auckland Fax 09 308 9456 Email [email protected] 10. Exercise Immunology review 4: 64-76, 1998 4