Reprinted with permission from Peak Performance.
Frustrating? Perhaps. But on a broader level, the role of sports nutritionist in professional football is seen as one of manipulating carbohydrate, protein, fat, fibre, fluid and micro-nutrient intake to maintain health, promote adaptation to training, and ultimately enhance or ??" in our particular sport ??" maintain performance over the course of a season.
The role of the nutritionist in football has evolved over the last five years. Compared to some practitioners, I am new in the sport (one dietician at a top Premier League club has been employed continuously for 13 years!), but I am sufficiently long-in-the-tooth to have detected significant change over this period.
At the time of writing, 19 out of 20 Premier League teams employ someone specifically to take care of the nutritional requirements of their players. This role is not always performed by a nutritionist or a dietician: in many teams the responsibility for implementing a nutritional support strategy falls on the shoulders of the sports scientist, conditioning coach or physiotherapist.
Nutrition In Football ??" A Brief History
Football was, for a long time, classed as an endurance sport due largely to the fact that a football match lasted at least 90 minutes. As a result, the nutritional requirements of football players were extrapolated from early scientific research carried out in relation to other 'endurance sports' such as running and cycling.
Yes, it is true that the duration of a football match is normally 90 minutes; however, the training loads associated with these sports are vastly different. On closer inspection it becomes clear that daily energy expenditure of professional football players may not be particularly high. Football players are generally inactive when not training and training load will vary, depending on factors such as the stage of the season, or whether tactical or fitness drills predominate in training.
Ron Maughan of Loughbrough University assessed the dietary intakes of two Scottish Premier League teams (he managed to get 51 players to perform 7-day weighed intakes) and found average daily energy intake to be approximately 2,620kcal and 3,050kcal respectively(1).
This is the only published data available on football players in this country and notwithstanding a recent finding that Japanese football players under-reported dietary intakes(2), this work does highlight lower energy requirements than were perhaps originally recommended for professional football players.
If football players were to consume 7-10g of carbohydrate per kg body weight each day (a recommendation found in many a textbook) then a quick calculation that included reasonable amounts of protein and fat would generate a daily energy intake closer to 4,200kcal. In Scandinavia this may be closer to the truth (Table 1).
Once the playing season gets underway the Scandinavian subjects typically train seven times per week compared with roughly four sessions in this country. So it is not surprising that energy intakes will exceed 4,000kcal in a country like Sweden.
|Nationality||Sample Size||Energy (kcal)||Carbohydrate (%)||Fat (%)||Protein (%)|
Not only were early dietary recommendations for professional football players slightly misjudged; a number of other problems existed in the delivery of nutritional support. Football was flooded with science and its analytical techniques, and experts employed by clubs exploited the 'measure everything' approach.
Blood, saliva, urine, lactate and expired air were all being indiscriminately extracted from players, often with little feedback offered in return. In the world of nutrition and football, science was calling the shots.
A New Climate Prevails
'An athlete's diet must be high in carbohydrate, moderate in protein, low in fat, include sufficient vitamins and minerals, and plenty of fluid.'
This was the original model with which many football nutritionists used to work. Although simple, much of it still holds true today. However, as our understanding of the game in this country has improved, nutritionists have been able to tease out strategies from each of the model's sub-sections that more closely match the requirements of our sport. What is different is that science no longer holds all the cards. Football has caught up with science and is now dictating where our efforts are directed.
For, example, the glycemic index of foods, a ranking of foods based on their immediate effect on blood glucose, has become a particularly useful tool in football.
Five years ago the approach in football was to advocate a high carbohydrate, low fat diet at all times. Any food that at all met these requirements would be recommended to players in a bid to maximize muscle glycogen storage for training and competition. Now a more measured approach is employed with the glycemic index and, to a lesser extent, the insulin index utilized in a bid to control body composition as well as carbohydrate provision.
Emphasis is now placed more on achieving optimum carbohydrate intake prior to matches, and during the recovery period after matches, particularly when some clubs find themselves involved in up to three games per week in the busiest part of the season.
Good attitudes to reducing fat intake are now commonplace in the modern player. Emphasis is placed on increasing intake of certain fatty acids that are found to be lacking in players' diets. When performing dietary analyses of players, low intakes of essential fatty acids (eicosapentaenoic acid, EPA; docosahexenoic acid, DHA) are consistently reported. Despite the appearance of oily fish in the canteens of football clubs, there may be a case for blanket supplementation in this particular group of sportsmen.
There is growing evidence that protein supplementation after training can promote protein synthesis and adaptation of muscle. The type, timing and amount of protein can be manipulated to enhance the adaptive response. The work of researchers such as Bob Wolfe and Kevin Tipton in Texas, and Mike Rennie in Dundee (whose primary interest has been likened to 'preventing older people falling down') has enabled us to design strategies of protein-intake that may promote better adaptation to training.
Interest in micro-nutrients has historically been associated with the free radical muscle damage hypothesis. In fact there is now some suspicion that the release of free radical species associated with exercise is necessary for adaptation of the cell to subsequent stressful events.
It is entirely feasible, although not proven, that free radicals play an important part in the adaptation of the muscle to hard exercise, and that increased consumption of some anti-oxidant nutrients might interfere with these necessary adaptive responses. Practitioners now warn against the use of mega-dose anti-oxidants.
Urine Indices To The Fore
Many indices have been investigated to establish their potential as markers of hydration status. Body mass changes, blood indices, urine indices and bio electrical impedance analysis have been the most widely investigated. Current evidence tends to favor urine indices, and in particular urine osmolality, as the most promising marker available.
Five years ago urine colour charts were commonplace on the walls of clubs' changing room toilets. Nowadays osmometers can be found at Premier League clubs. Urine samples provided by players can be analysed in approximately 30 seconds and the machines quickly identify dehydrated subjects.
A recent preliminary report has suggested that American football players who repeatedly suffer muscle cramping in training and competition have greater sweat losses and a higher sweat sodium content than players matched for fitness and other factors but who do not suffer from muscle cramps(4). Data on sweat electrolyte losses in football players in training are now being collected in a bid to identify those players at risk of potentially debilitating muscle cramp.
Assessment of body composition plays an important role in nutritional evaluation, particularly in a sport obsessed with body image. Along with body mass, an estimation of body fat percentage (or sum of skin folds) has traditionally been the requisite regular test demanded by football managers.
In addition to the usual body composition assessment methods, a number of other techniques are being utilized in the modern game. The evaluation of skeletal muscle mass, in particular appendicular skeletal muscle, mass can contribute important information to the assessment of nutritional status because it reflects the body protein mass.
A major impediment to determining muscle mass is the lack of suitable, easy and non-invasive methods for estimating muscle mass. Lee and others(5) have developed anthropometric prediction models validated against the 'gold standard' method of magnetic resonance imagery to estimate total body skeletal mass using skin fold thickness and limb circumferences. These have proved useful in tracking changes in muscle mass associated with inactivity or resistance training protocols.
Although expensive, dual-energy X-ray absorptiometry (DEXA) is proving a valuable tool for body composition assessment, particularly with injured players recovering from a period of inactivity. If you are lucky enough to have access to DEXA at a university or hospital, this technology is able to identify accurately fat and lean tissue and can be used both for whole-body measurements of body composition and for providing estimates of the composition of specific sub-regions (e.g. trunk or legs).
The DEXA instruments differentiate body weight into the components of lean soft tissue, fat soft tissue and bone based on the differential attenuation by tissues of two levels of X-rays.
Indirect calorimetry is used to estimate daily energy expenditure of individual players, particularly those who are undergoing a period of inactivity through injury. Measuring the oxygen consumption of an individual and time spent during different activities allows a picture of energy expenditure to be drawn. This information can then be used to prescribe eating and drinking plans that match more precisely players' energy requirements.
These are just a few examples of where science and football have worked together to develop player and sport-specific nutritional support programs. Science should be committed to meeting the demands of football and not vice versa. It may sound obvious, but it wasn't always so.
The Challenge Ahead
Despite the progress that has been made in our understanding of the demands of football, there is a need for continued improvement. No other sub-discipline of sports medicine comes with so many contrasting views of what is right and wrong.
The 'Zone' diet, the 'Atkins' diet, mass supplementation, the concept of the 'nutritional guru' ??" all are still prevalent in the modern game. Players are becoming more demanding due to conversations with other players from other teams, and also other athletes from other sports. Players from overseas bring with them their own ideas (nearly always related to vitamin intake), but often lacking in scientific support.
In addition, at present there is a fundamental mismatch in what players and practitioners view as important. Players believe in supplements, extra vitamins and minerals: anything that involves increasing muscle mass, and reducing energy intake to achieve 'lean' body composition.
Scientific research, on the other hand, demonstrates that players should concentrate more on appropriate energy intake, and high carbohydrate and fluid intake.
Football is steeped in tradition, which many people wrongly write off as Luddite-type conservatism, or little better than old wives' tales passed around the old boys' network. It is true that many coaches and support staff are employed from within, but it is also true that these people know the sport and its peculiarities better than anyone.
Furthermore, the practice of employment from within will eventually spawn a new breed of coaches that have had, one hopes, more positive and enlightened experiences of sports nutrition. There is already evidence of this taking place.
Back To The Fish & Chips?
Of course providing a cutting-edge nutritional support programme has no value unless appropriate education (one that is both stimulating and imaginative) is implemented. In a world dominated by R'n'B, fast cars and Louis Vuitton washbags, it is important to pitch your educational material appropriately.
'Healthy eating' on its own just does not wash with Premier League football players. Science and technology, pitched correctly, most definitely do. For all the advances science has made, the most important lessons that nutritionists have had to learn are 'respect the sport' and 'know your place'. It is sobering to note that Real Madrid, arguably the world's best football team, employ no fewer than nine masseurs but do not employ anyone to take care of the players' nutritional requirements.
Finally, my personal working title for this article was 'The role of fish and chips in modern football'. Five years ago I walked into a football club and one of the first changes I made was to remove the fish and chips from the post-match menu. This wasn't a popular move and it would be dishonest to say that anything that has been offered to the players since has received anything like the same enthusiasm. Should I go back to fish and chips?
Well, potato is a high glycemic index carbohydrate food thought to be preferable for the recovery of muscle glycogen stores, and fish is a complete protein source possessing essential amino acids ideal for stimulation of muscle protein synthesis. Most importantly, most of players will definitely eat this dish. OK, the high fat content will probably interfere with the glycaemic response of the potato, and, of course, there are other health promotion implications to wrestle with.
In actual fact, I probably won't return to post-match fish and chips for the players, however popular this would be, but this real-life example does highlight the fact that for all the rewards that science and nutrition has to offer, these can only be achieved if we respect the traditions of the sport and take the players along with us.
- Br J Sports Med, 31:45-47.
- J Sports Sci, 20:391-7
- Int J Sport Nutr, 8:230-240.
- Med Sci Sports and Exerc, 35:S48
- Am J Clin Nutr, 72:796-803.