Title: Soccer and Nutrition
Key words: Glycogen, energy intake, energy expenditure, carbohydrates, fats, proteins, fluid, micronutrients
Date: July 2000
Category: 12. Sports
Author: Dr M Draper
Soccer is known and loved throughout the world. From the child on the street corner to the professional athlete playing in a World Cup Final, soccer stirs the heart and minds of us all, perhaps more than any other sport.
As one of the world's best loved games, soccer is an excellent way of exercising. It combines the benefits of team play, a wide range of different skills and can be played at all levels, at all ages, by males and females alike.
All players want to improve their performance and many spend hours each week in coaching and training sessions. Yet, the extra benefits that can be gained from the right diet are often overlooked, or may even be unknown. This article is designed to fill that gap.
Soccer and Nutrition aims to help players of all skill levels understand how, what and when they eat can affect both how they train and how they play. The special needs of female and young players are also addressed.
Soccer and Nutrition is based on the conclusions of the Consensus Conference on "Foods and Nutrition for Soccer Performance" held in Zurich in February 1994.
The Demands of Soccer
Soccer is a high intensity, intermittent activity which requires both strength and endurance over a period of 90 minutes.
A top class male soccer player will cover approximately 11km (6.8 miles) during a match. Tackling, jumping, accelerating, turning and even getting up from the ground will place further demands on him. He will also need to perform a number of perceptual and motor skills.
During a soccer match, around 1000m (1100 yds) is covered in high intensity running; this will include around 20 very short, fast sprints.
This combination of length of play and quick bursts of high intensity exercise tends to lead to fatigue towards the end of a match. Some players can significantly reduce their energy stores during a game; they literally run out of fuel. Obviously, this seriously limits their performance and can affect the outcome of a match.
Fatigue will affect individual players differently. This will reflect both the effort they have put into the game and how well they have trained and prepared for it.
Knowing how to restore and preserve energy stores is therefore a vital part of player preparation.
In addition, players lose a considerable amount of fluid during a game. In normal weather conditions a player can lose 2kg (4.4 lbs) of body mass, so rehydration is critical too.
However, meeting the demands of the game means more than just getting enough energy and water. The variety of turning manoeuvres and the repeated impacts experienced by players puts great demands on their skeletal and muscular systems. Having the right nutrients can reduce the risk of injuries. Intake of all nutrients must therefore be addressed.
Energy is provided mainly by carbohydrate and fat. Carbohydrate, whether as sugars or starches, is broken down in the body into glucose and either goes to the blood for immediate energy use or is stored as glycogen. Some is stored in the liver until it is needed to raise the blood glucose level and to supply the brain with glucose. The majority is stored in the muscles themselves. Fat is stored in the adipose tissues and muscle cells.
The body uses oxygen to burn up the carbohydrate and fat to provide energy for the muscles to work. This method of energy production is known as aerobic metabolism. The alternative method, anaerobic metabolism, utilises only carbohydrate and does not require oxygen.
During low intensity exercise, the body works aerobically and fat accounts for more than half of energy production. As exercise becomes more intense, carbohydrate becomes the major fuel source. As exercise intensity increases further, the point comes where the body cannot take up enough oxygen to sustain aerobic metabolism; this is known as the maximum oxygen uptake level. Beyond this point, for example, during rapid sprints, energy can only be produced anaerobically, mainly utilising carbohydrate. Anaerobic metabolism uses up carbohydrate very quickly. The process also produces lactic acid, which affects the muscles, causing fatigue.
Training enables the muscles to take up more oxygen from the blood, i.e. it raises the maximum oxygen uptake level, so that energy is produced aerobically for longer. That is why the trained athlete is able to exercise with apparently less exertion than the untrained person.
Training also increases the capacity of the muscles to store glycogen. Glycogen depletion limits the ability of soccer players to maintain high intensity running performance, especially during the latter stages of a match. Without glycogen, the muscle will be forced to rely on fat as fuel. Since fat can only be metabolised at the lower levels of exercise intensity, the player will be forced to slow down.
The level of muscle glycogen prior to the match will influence performance towards the end of a game. This has been shown to be a significant factor, even at the top levels of the game.
A Swedish study looked at thigh muscle glycogen concentrations of five players before, at half-time and after a non-competitive match. It compared these with four other players who started the match with low glycogen levels as a result of physical exercise the day prior to the game. In the group of four players, the muscle glycogen storage was almost depleted by half time.
Good sources of carbohydrate are sugars, fruit, rice, bread, pasta, potatoes, breakfast cereals, confectionery, cakes and soft drinks.
Energy values: 1g carbohydrate = 4 Calories (4 Kcal or 17 kJ)
Carbohydrate is likely to provide the majority of energy during a soccer match. It is an important contributor to aerobic metabolism and is the only fuel available for high intensity, anaerobic exercise.
It is well accepted that endurance exercise performance is enhanced by increasing carbohydrate availability before and during strenuous exercise. There is now increasing evidence that increased carbohydrate availability will enhance high intensity exercise performance as well.
However, busy competition and training schedules, inadequate recovery time and muscle trauma can make it difficult to keep up adequate liver and muscle glycogen reserves. Soccer players, therefore, need to make the effort to ensure they have enough carbohydrate in their diet.
To guide players towards selecting a high carbohydrate diet the glycaemic index can be used. The glycaemic index refers to the rate of absorption of carbohydrate food.
To ensure adequate glycogen resynthesis, soccer players should be counselled to consume 55-65% of their total daily energy in the form of high to moderate glycaemic foods. These foods are basic foods known in most geographical regions and appropriate to all cultures.
Food eaten 1 hour before exercise should provide 1-2 grams of carbohydrate per kg of body weight. If food is eaten 4 hours before exercise, the recommended carbohydrate content is 5 grams per kg body weight.
Simple carbohydrates (sugars) are quicker to digest than complex carbohydrates (starches); liquids are easier to digest than solids. Players hesitant to eat solid foods immediately prior to competition should be guided toward liquid carbohydrates.
Players are also likely to benefit from taking in carbohydrate during a match. This has been shown to reduce the overall amount of muscle glycogen used and to enhance performance.
During endurance exercise, consuming 25 grams of carbohydrate every 30 minutes has been found to delay fatigue.
Carbohydrate taken in the recovery period will help replenish liver and muscle glycogen stores. This can be in the form of complex starches or simple carbohydrates (except fructose), in either liquid or solid form.
Players should be encouraged to consume carbohydrate rich foods as soon as play stops and to maintain consumption over the next two hours. This is the time when glycogen stores can be most efficiently replenished.
An effective way of increasing muscle glycogen stores is repeatedly to deplete muscle glycogen by intensive exercise, followed by high intakes of carbohydrate. This is often referred to as 'supercompensation'. However, this can cause fatigue, irritability and decreased cognitive abilities. An alternative is the 'over compensation' method, whereby for three to four days before competition a reduced exercise programme is undertaken in conjunction with a high carbohydrate diet.
Whichever regime is preferred, food intake should include easily digested high carbohydrate foods that are familiar, palatable and psychologically satisfying. As with all food choices, individual food preferences need to be taken into account.
Different players will increase their carbohydrate intakes with widely different food selections; if they are able to select the foods they prefer, they are more likely to stick to the recommended intake levels long term.
Good sources of fat are oil, butter, margarine and other spreads, meat, milk, fish and nuts.
Energy values: 1g fat = 9 Calories (9Kcal or 37kJ)
Dietary fat intake is useful in meeting the increased energy demands of exercise but may need to be reduced to allow for increased carbohydrate intake. Fat intake should not exceed 30% of total calories, with less than 10% of total calories as saturated fats.
Good sources of protein are meat, milk, poultry, fish, dairy foods, nuts, eggs, legumes and pulses.
Energy values: 1g protein = 4 Calories (4Kcal or 17kJ)
Studies with continuous exercise, at a work rate and duration similar to soccer, have indicated that protein may contribute around 10% of total energy production. Amino acids (which are components of protein) can be turned into energy for exercise, using oxygen. During moderately intense, prolonged exercise, amino acids serve as an important auxiliary fuel source as glycogen availability is reduced. Endurance training further enhances amino acid oxidation, thus potentially further delaying fatigue.
Protein has traditionally been associated with bodybuilding, although the evidence to support the theory has not been clear cut. Recent experiments suggest that dietary protein intake in excess of the current RDA (Recommended Daily Allowance: 10-16% of energy), combined with heavy resistance training, may well enhance muscle strength/size development.
Failure to consume adequate dietary protein will cause significant problems. When protein is used as a fuel source, amino acids are lost from the body. If they are not replaced via the diet, chronic losses in muscle strength will result.
The current RDA for protein was determined on individuals who are essentially sedentary and is insufficient for both strength and endurance athletes.
The recommended protein intake for male soccer players is about 1.4 - 1.7 g/kg/day i.e.: 175 - 212 % RDA.
This assumes that the protein will be from a high quality source, (e.g. meat and dairy products). Those who follow vegetarian diets will need slightly higher intakes (10-20 % more protein, i.e.: biological usefulness.
However, it does not follow that the more protein that is eaten the more muscle will develop. Above 175% RDA protein synthesis plateaus. Extremely high protein intakes (>2g/kg/day), which are routinely consumed by many athletes, provide no advantage and could be hazardous.
Any extra protein required by soccer players is easily supplied by the extra food eaten to meet their increased energy demands.
Good sources of vitamins and minerals are fruit, vegetables, nuts, fish, meat, eggs, dairy products and of course, combinations of these ingredients.
Vitamins and minerals play an important role in energy metabolism. Deficiency of one or several micronutrients can impair exercise capacity. Vitamins and minerals are found in a wide range of foods and intakes are positively associated with energy intake. Eating a varied diet usually provides enough micronutrients for everyday needs, yet many athletes take supplements as a back-up.
Dietary surveys of athletes engaged in a range of different sports show that they tend to have more vitamin C than the RDA. Vitamin B6 in many groups has also been found to be below the RDA. Male ballgame athletes tend to have enough calcium and iron. Supplements will make up for any shortfalls, but there is no evidence that extra micronutrients further improve performance.
Nutritional education should concentrate on food intakes and macronutrients. Positive changes in macronutrient composition (reduced fat and alcohol, increased carbohydrate intakes) will also result in increased micronutrient intake. Emphasising single micronutrients is not recommended.
It is more important to make positive changes to the diet than to take supplements.
The resting temperature of the body is 37C (98.6F). During exercise, heat is produced and the body has to find a way of keeping body temperature within the range 38-40C (100.04 - 104F). On a hot day, when the ambient temperature is higher than skin temperature, this adds to the body's heat load. Sweating allows heat to evaporate from the skin surface and keeps body temperature down; but it also results in dehydration and electrolyte loss which, in turn, impairs performance.
Severe dehydration is potentially fatal. Exercising while dehydrated causes body temperature to rise quickly and this can lead to heat illness. Even when the weather is cold, significant sweat loss will occur, leading to a degree of dehydration.
In sports where protective clothing is worn (e.g. American football), severe heat stress is a risk. This is not usually a problem for soccer players wearing traditional soccer kit and playing in normal conditions; however, the risk of heat stress inevitably increases during hot weather and tournaments.
Exercise performance can be impaired when an individual is dehydrated by as little as 1% of body weight: losses above 5% body weight can decrease the capacity for work by about 30%. Dehydration also adversely affects cognitive performance, which is an important aspect of soccer.
Fluid intake before and during the game can help avoid dehydration. Fluid requirements will depend on work rate, the weather and the individual player. Some indication of a player's fluid requirements can be gained by recording body weight before and after training and competition. Studies have shown a loss of 1-2.5 kg (2.2 -5.5 lbs) during games played in temperate climates, with the loss being greater in international level games and less in players performing at a lower standard. A sweat loss of around two litres is fairly common; in hot conditions as much as four litres has been recorded.
Adding carbohydrate to drinks is a useful way of increasing fuel supplies, although high concentrations can delay gastric emptying and, thus, delay water absorption from the intestine. Carbohydrate depletion results in fatigue and reduced playing performance, but is not life threatening. The composition of drinks is influenced by the relative importance of the need to supply fuel and water; this in turn depends on the individual player and the ambient temperature and humidity. In hot weather, provision of water is the first priority and carbohydrate concentration could be lower. Carbohydrate should not be excluded altogether even in these conditions; drinking plain water alone reduces the concentration of sodium in the blood, which reduces the stimulus to drink, and stimulates urine output - this can delay the rehydration process.
Opportunities to drink during a game are limited so players must ensure they are fully hydrated beforehand. Extra fluids should be taken with breakfast and lunch on match days and 10-15 minutes before the game begins. Fluids should be taken at half time.
To ensure that drinking during play does not cause gastrointestinal problems, players should become accustomed to drinking in training. Players should experiment during training to find out the type, amount and frequency of drinks that best meet their needs. Of course, drinking during training is equally important to counter the dehydrating effect of training itself.
In hot and humid weather, fluid intake should be increased. This is particularly important when teams from temperate countries visit hotter climates. Additional fluid should be taken whenever there is a stoppage in play for injury. Extra care should be taken during tournaments; full recovery between games will not occur unless water and electrolyte losses are replaced.
Fluid replacement after exercise is an essential part of recovery. Carbohydrate-containing drinks have the added benefit of restoring glycogen stores at a time when replenishment is most effective. Getting the carbohydrate concentration level right remains important nevertheless.
Most commercial sports drinks are suitable for both rehydration and refuelling. They should be readily available and ones which the player enjoys. Drinks which cause abdominal discomfort should be avoided. Enough fluid should be consumed to ensure a normal urine output, which should be pale yellow in colour.
In most situations, electrolyte replacement will occur through normal food intake in the hours after exercise. Electrolyte supplementation is necessary only when the sweat losses are unusually large or where there is no opportunity for solid food intake before the exercise resumes.
Female and young soccer players
Female and youth players follow the same playing patterns as male adult players, combining short bursts of high intensity exercise with longer periods of low intensity exercise. While much of the advice given to adult male players applies to these two groups, they have some additional needs, which should be met.
Even at the highest level of the game, female players are usually part time. They have to combine the demands of training with their full time occupations. Furthermore, training generally takes place in recreational time, which is when main meals are usually eaten. Female players have high energy needs but often limited time to prepare and consume meals. Since females tend to be the main meal providers in the household, their partners and family need to be encouraged to help them by providing suitable meals after training or playing.
Studies have found that many female athletes are influenced more by a desire to be thin than by the need for adequate energy intake. In contrast, female soccer players generally do not perceive low body fat as crucial to performance and so they tend not to over-diet. Nevertheless, the utmost sensitivity needs to be used when advising young female players on their dietary habits and advisors should remain on the lookout for eating disorders.
Because youth games have more rest breaks and shorter playing times, total energy expenditure compared with adult soccer is reduced. Nevertheless, young players still need to support relatively high levels of energy expenditure in addition to the energy they need for growth.
Carbohydrate is just as important for female as male players. Given the difficulty female players can have in fitting in proper meal times with playing and training schedules, they should be encouraged to eat high carbohydrate snacks at regular intervals.
For those consuming more than 45 kcal/kg (body weight)/day, a minimum of 55% total energy intake should come from carbohydrates. For females consuming less than 45 kcal/kg/day, carbohydrate consumption should be a minimum of 6g/kg/day. As with males, carbohydrates are needed to support training as well as playing and should be consumed at appropriate times before and after exercise, on a seven day a week basis.
The high carbohydrate diet should be sustained even outside the playing season, when overall energy intake will need to decrease to compensate for reduced energy expenditure. Nutritional counselling should focus on substituting carbohydrate for fat to avoid increasing energy intake.
For young players, the overcompensation rather than the supercompensation approach may be more suitable. However, since children preferentially utilise fat, it is not certain to what extent carbohydrate loading will improve their performance.
Young players do not need more dietary fat, even though their muscles rely more on fat than carbohydrate.
Female players might need less protein. There is evidence that protein use during endurance exercise is greater in men than in women.
Young players' daily protein requirements (per kg body mass) are higher, as shown in Table 5.
Females with lower energy intakes often have low intakes of calcium, magnesium, iron and zinc. Though this may not be a problem for most players, supplements can be useful for others. Females with frequent or large menstrual iron losses and those on vegetarian diets are more at risk of iron deficiencies. Female players should therefore be assessed at least once a year and may need supplements. Calcium, and perhaps vitamin D supplements might also preserve bone density in athletes with menstrual irregularities. To ensure iron and calcium intake, female players should not be encouraged to adopt vegetarian diets.
Little is known about intakes for young players. The few studies which have been done show no significant shortfalls.
Young players' core temperature rises faster, which calls for stricter enforcement of hydration. They should be given fluids that are both effective in rehydration and liked.
Table 5 - Protein needed per kg body mass per day (g/kg/d)
5-10 years old girls and boys 1.2g
11-14 year old 1.0g
15-18 year old 0.8g
Sedentary adults 0.8g
Adult female soccer players 1.4 - 1.6g
Adult male soccer players 1.4 - 1.7g
Time must be taken to assess players' training, pre-competition and post-competition eating practices. Focus should be on critical dietary components, such as adequacy of intakes of total kilocalories and grams of carbohydrate.
The players themselves also need to learn how to and what to eat for maximum benefit. This requires education materials, dietary counselling and monitoring if dietary intake. Players should be encouraged to monitor the carbohydrate foods they eat (see Tables 2-4), and after a period of days they should review the adequacy of intake and change their diet as appropriate.
Players should be encouraged to check food labels for carbohydrate content and energy and to plan intakes to suit their individual needs. It is essential that coaches and other involved in providing nutrition advice to players are aware of the players' food preferences to maximise the chance of dietary change being maintained long term.
Soccer is a worldwide game. Participants include young and old, male and female, amateur and professional, healthy and less healthy who all play with the common purpose of doing well at the game they hold in such high regard. It is recognised that different cultural, tactical and other factors may influence individual nutritional recommendations.
Soccer training and competition results in an increased energy demand that must be accompanied by an increased energy intake to sustain performance and maintain ideal body weight...In elite players, the average work rate corresponds to about 70% of maximum oxygen uptake. This corresponds to an energy cost of about 1000 to 1500 kcal (4000-6000 kJ) for a 70kg (154 lbs) player. The anaerobic energy systems are also heavily taxed during periods of match play. Repeated bouts of high intensity exercise during competition and training will deplete the muscle and liver glycogen stores.
Carbohydrate depletion may contribute to fatigue and reduced capability for performance during a soccer match. Soccer players engaged in strenuous competition and training should be encouraged to consume a diet that is relatively high in carbohydrate (at least 55% of total energy). If energy intake is low, or if carbohydrate requirements are high (e.g. during periods of intensive training and competition), the dietary carbohydrate intake should be increased even further. In practice, soccer players often experience difficulty in achieving adequate dietary carbohydrate intakes. They should be encouraged to consume a variety of simple and complex carbohydrate foods, in liquid and solid form during preparation for, and recovery from, training and competition.
The high rates of metabolic heat production, during soccer training and competition, will lead to significant seat loss. Dehydration will impair exercise performance and may result in heat-related illness. Fluid intake before and during the game will reduce to degree of dehydration and can also supply carbohydrate to supplement the body's limited carbohydrate stores. Furthermore, the inclusion of electrolytes, particularly sodium, and carbohydrate in beverages or solid food consumed after a soccer match or training will promote recovery.
Soccer play makes high demands on both endurance and muscle power. The daily protein intake of soccer players should be about 1.4 - 1.7g/kg body mass. This recommendation is easily attained, without supplementation by most players who have free access to a wide variety of foods in sufficient quantity to cover their daily energy expenditure.
Female athletes sometimes restrict energy intake due to their desire to lose or maintain body weight. In extreme cases, this motive can result in eating disorders, but there is no clear evidence to suggest that this problem is common among female soccer players.
Despite low energy intakes and thus low mineral intakes in several groups of female ball-game players, there is no evidence that performance benefits from micronutrient supplementation. Nevertheless, iron therapy might be beneficial for iron depleted individual. In athletes with infrequent or irregular menstruation, supplementary calcium might help to preserve bone density.
The general dietary needs of child and adolescent players are similar to those of adults. There is at least one, however, important difference. During dehydration, children's core temperature rises faster than that of adults, which calls for stricter controls of fluid replenishment.
To maintain a consistent balance between energy and nutrient intake and requirements, players should receive dietary advice from a qualified nutrition professional to cover all phases of the year not just the competitive season.
Zurich, February 11th, 1994
International Scientific Consensus Conference on Nutrition and Soccer
Carbohydrate rich foods with a high glycaemic index.
These foods are recommended anytime for training, 3-4 hours pre-match and post-match for rapid recovery and glycogen resynthesis.
|FOOD GROUP||FOOD ITEM||SERVING SIZE (gm/ml) giving 50g carbohydrate|
|Grains||White bread Wholemeal bread Rye bread (light) Bagel Pastry (shortcrust) Rice (wholegrain) Rice (white)||201g 120g 104g 89g 90g 196g 169g|
|Breakfast cereals||Cornflakes Muesli Shredded wheat Weetabix||59g 76g 74g 71g|
|Biscuits and confectionery||Wholewheat semi-sweet biscuits Crispbread (rye) Plain cracker Chocolate nougat bar (contains sucrose and glucose)||76g 71g 66g 75g|
|Vegetables||Sweetcorn Broad beans Parsnips Potato (instant) Potato (boiled) Potato (baked)||219g 704g 370g 310g 254g 200g|
|Fruit||Raisins Banana||78g 260g|
|Sugars||Glucose Maltose Honey Sucrose Molasses: 113ml Corn syrup||50g 50g 67g 50g 63g|
|Beverages||6% sucrose solution 7.5% maltodextrin and sugar 10% cornsyrup carbonated drink 20% maltodextrin||833ml 250ml 500ml 250ml|
Carbohydrate rich foods with a moderate glycaemic index.
These foods are recommended anytime for training. 3-4 hours pre-match, and post-match for rapid recovery and glycogen resynthesis.
|FOOD GROUP||FOOD ITEM||SERVING SIZE(g or ml)|
|Cereals||Spaghetti (Macaroni) Noodles (oriental)||198g 370g|
|Breakfast cereals||Wheatbran nuggets Porridge (oatmeal)||232g 69g|
|Biscuits and Confectionery||Oatmeal biscuits Sweet, plain biscuits Sponge cakes||79g 67g 93g|
|Vegetables||Potato (sweet) Yam Potato chips||249g 168g 100g|
|Fruit||Grapes (black) Grapes (green) Orange||323g 310g 420-600g|
Carbohydrate rich foods with a low glycaemic index. These foods are recommended anytime during training, and post-match, along with high and moderate glycaemic foods.
|FOOD GROUP||FOOD ITEM||SERVING SIZE (g or ml) Giving 50g carbohydrate|
|Fruits||Apples Apple sauce(sweet) Cherries Dates (dried) Figs (raw) Grapefruit(canned) Peaches Plums||400g 290g 420 78g g 526g 300g 450-550g 400-550g|
|Legumes||Butter beans Baked Beans Haricot beans Chick peas Red lentils Navy beans||292g 485g 301g 305g 294g 238g|
|Dairy Products||Ice cream Milk(whole) Milk(skim) Yoghurt(plain, low fat) Yoghurt(fruit, low fat)||202g 111g 101g 800g 280g|