Evidently, American swimming champion Michael Phelps was not a fan of food supplements. As the media reported in 2008, when training he ate 12,000 calories a day, mostly in fats, carbohydrates and sugars. Viktor Röthlin, a recently retired Swiss marathon runner and former European Champion, delighted in eating rösti (fried grated potatoes) the day before a race. Meanwhile, 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 sports. In short, the importance of carbohydrates for physical performance and recovery has now been proven, as have adequate hydration and the need to compensate mineral salts lost in perspiration.
Biochemist Jacques Décombaz’s professional studies focussed 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 runners(1) and kindly acted as consultant in the preparation of this piece. Décombaz’s articles take us through the rise to fame of intricate molecules in the world of sport over the past twenty years, with accurate descriptions of metabolic mechanisms and of both the objectives and results.
What remains of all this today? Time has dampened 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 recuperation 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, the chemistry of such interactions has proven 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 also strongly promotes water retention. Hence, for athletes who want to keep their weight down, ingesting creatine is potentially counter-productive.
Small droplets of fat are also present in muscle fibres and serve a similar function to "handy small fuel cans for a carburettor". Scientists at the Nestlé Research Center(2) have been focussing on these droplets, called intramyocellular lipids (or IMCL) for some time, although their findings have not yet been substantiated. These small droplets are nevertheless very interesting in terms of nutrition and sport, as the muscles of endurance runners 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 an abundant and regular source of energy and lipids provide them with two times more calories than the same amount of carbohydrates. These are stored as conveniently as possible, i.e. close to where the calories will be burned during prolonged exertion. Researchers imagined that improving runners’ capacity for storing such fat might provide a source of energy over a longer period of time. Yet so far such dietary measures have not influenced performance positively.
Le Mmmille pattes, part of the Swiss-French Spiridon romand magazine. See Jacques Décombaz’s articles under ‘Propos de table’ on www.spiridon.ch (select Divers from the left-hand menu).
In partnership with the Clinical Research Department of the University of Bern.
