Nourishing performance in sport
Do athletes need to take food supplements to reach the top of their game? Twenty years ago, many scientists claimed that biochemistry and nutrition would boost performance in sport. The promising results of hundreds of studies and an avalanche of new food supplements seemed to prove them right.
Fortified food and food supplements used to be confined to chemist’s shelves and the gym but, over the past fifteen years, they have invaded supermarkets and online shopping sites in their hoards. Supplements specifically for competitive athletes promise faster and more efficient recovery, increased muscle mass with less fat and/or optimisation of effort. The mysterious names of some of the molecules herald powers that appear scientifically proven to the layman: carnitine, creatine, antioxidants, beta-alanine...
Rösti, ugali and calories galore
The American swimming champion Michael Phelps was apparently not a fan of food supplements since, in 2008, the media reported that when training he ate 12 000 calories a day mostly in fats, starch and sugars. Viktor Röthlin, a recently retired Swiss marathon runner and former European Champion, willingly ate rösti (grated potato patties) the day before a race. On the other hand, Kenyan rivals still swear by ugali, a sort of porridge made from cornmeal. As any sport enthusiast knows, it helps to eat a plateful of pasta the day before physical activity and to eat the pieces of banana offered during endurance exercise. In short, the importance of carbohydrates in physical performance and recovery has now been proven, as have adequate hydration and the need to compensate mineral salts lost in perspiration.
From the laboratory to the torment on the sports ground
Jacques Décombaz’ professional studies focused on the nutritional physiology of exercise and physical performance. He aimed to measure the value and effectiveness of nutritional intervention on energy metabolism during physical exertion. He is now retired, but continues to write a column on nutrition in a Swiss magazine for fellow runners1 and kindly acted as consultant in the preparation of this piece. Décombaz’ articles always give accurate descriptions of metabolic mechanisms and of both the objectives and results as he leads us through the rise to fame of intricate molecules in the world of sport over the past twenty years. What remains of all this today? Time has calmed the initial enthusiasm. For example, molecules such as carnitine and creatine have had their heyday, the first for its role in burning fat and the second for speeding up recovery and improving capacity for exercise. Laboratories have carried out extensive research on the interactions of these molecules with the body during phases of exertion and recovery. However, such chemistry is more difficult to influence in real life. Carnitine and creatine are molecules that the body produces naturally and supplementing them has not actually enhanced athletic performance (although creatine has proved useful in rehabilitation). Even if creatine intake helps increase muscle mass, it especially increases water retention and, for an athlete who wants to stay lightweight, this is potentially counter-productive.
What can we do with these droplets of fat?
These small droplets of fat are present in the very core of muscle fibres, similar to "small fuel cans next to the carburettor." Scientists at the Nestlé Research Center2 have been focusing on these intramyocellular lipids (or IMCL) for some time, although their findings have not yet been put into practise. These small droplets are nevertheless very interesting in terms of nutrition and sport, as endurance runners’ muscles are streaked with them. While sedentary people may have fat on their hips, they actually have half as much fat in their muscles as a runner has. Runners need a copious and regular source of energy so they consume ample fats, which provide twice as many calories as carbohydrates for the same weight. They then store fat as conveniently as possible, i.e. close to where it will be actively used during prolonged effort. Researchers imagined that improving runners’ capacity for storing such fat could provide a source of energy over a longer period of time. Yet so far such dietary manipulations have not positively influenced performance.
Wishful thinking or good for your morale?
"Since he stopped eating gluten, Novak Djokovic became world number one tennis player!" One company is not at all shy about using this slogan to promote the powers of its gluten-free products. Yet, while a gluten-free diet is highly fashionable today, dieticians and doctors are preaching to the wilderness when they assure us that cutting out gluten is of no benefit to health unless you suffer from gluten intolerance. We remain desperate to believe that this regime is our modern-day panacea. Sportsmen and women in their quest for achievement are no different to common mortals. From time immemorial, humans have sought to improve their strength, particularly by favouring certain types of food or ingredients. The athletes of antiquity saw the virtue of eating beef from a bull and pork and also of drinking mead. Today, such wishful thinking is channelled towards pills, jellies and drinks fortified with vitamins, caffeine, proteins, carbohydrates, minerals and other micronutrients.
Useful or useless?
Supplements may however be justified in the context of elite sport, where the body is submitted to exceptional physical constraints. This is where encouraging results of experiments performed in vitro have the best chance of affecting the biological side of exercise. It is a question of small individual dietary improvements and/or targeted supplements optimising the ‘energy machine’, depending on the kind of exertion (duration, power, repetition...). However, dietary supplements have only modest influence on sporting success, as they account for a mere 1% or even a fraction of a percentage of improved performance. Yet, for someone with the ambition to win, that little extra is part of a whole that, on any given day, could lead to victory and even to breaking a record.
Simple, practical and easy to keep
We can understand that, for sport enthusiasts or casual athletes, ‘sophisticated’ dietary supplements actually have insignificant impact on performance. This is quite simply because casual athletes have not yet stabilised their physical skills (power and muscle strength, lung capacity...) at even the lowest level at which targeted food supplements could provide that little something extra which could actually make a difference. For casual sport, a balanced diet, eating food that is rich in carbohydrates and fats at the right times, adequate hydration and a training strategy that alternates phases of effort and recovery are all the key to sport that brings both pleasure and progress. Nonetheless, energy bars and sports drinks can be very practical in certain circumstances. Such products are compact, resistant, nutritious, digestible and easy to keep. They therefore provide a great snack for a trek in the mountains, prevent drowsiness and reassure sportsmen they are well prepared!
