From the ancient Olympic Games to the present day, the control of per diem expenses has been used as an attempt to improve physical performance in sports. The writings of ancient Greek philosophers and physicians report different strategies that athletes developed in the realm of the human and the divine, combining food and magic, to prepare for their competitions. Athletes consumed animal meat -beef, goat, bull or deer-, fresh cheese, wheat, dried figs, wine and some special 'concoctions'.

Today, athletes are still looking for in food, and in the 'magic' of different nutritional supplements -such as vitamins-, that small advantage to improve a tenth of a second or two centimeters in their sporting performance. A tiny difference that means going from oblivion to glory. But can nutrition help you succeed in sport? Undoubtedly, yes.

A clear case in point is soccer. It is an accepted fact that muscle glycogen - i.e. the glucose stored in the muscle - is crucial to a player's performance. Thus, to achieve adequate muscle reserves, an adult soccer player's diet should contain about 500 grams of carbohydrates per day. This translates into a varied and balanced per diem expenses where potatoes, bread, rice, fruit, legumes, cereals and pasta are the main ingredients. The player who accumulates less glycogen before the start of the match runs less meters and runs more slowly.

Paula Radcliffe is another example of the close relationship between per diem expenses and sport. This British marathon runner arrived at the 2004 Olympic Games in Athens with the world record under her arm and became the undisputed Gold medal contender. However, she was not able to finish her agonizing participation. She ran out of strength a few kilometers before the goal. Fans remember how she was always in the lead of degree program, without eating or drinking, until she suffered the "pájara": a condition associated with insufficient levels of glucose in the body that forced her to abandon the race.

The image of the runner wrapped in tears, helplessly standing next to the sign announcing the 30th kilometer of the competition, is a sad example that reminds us of the influence of nutrition on physical performance, even though many athletes - including those competing at the highest level - are still unaware of it. Looking back, the early years of the 20th century saw a major breakthrough in the research on essential nutrients and their role in physical performance. Despite this new knowledge, competitors in the first edition of the Tour de France, held in 1903, and throughout the first two decades of its development, obtained their food from bars along the route and drank from fountains along the way.

It was around 1920 when it was first suggested that carbohydrate intake during exercise could lead to improved physical performance. Those advances lay dormant for several decades in the drawers of laboratories and in the pages of scientific journals. In 1936, at the Berlin Olympics, the diet of Olympic athletes was focused on meat. They had two steaks per meal. Also chicken, in an average of almost half a kilo of meat per day. Before the competitions the usual menu consisted of up to three steaks and eggs supplemented with a meat juice extract. Others emphasized carbohydrates. This was the case with the English, who used to eat 'porridge' - a mixture of flour cooked with water and salt; the Japanese, for their part, ate half a kilo of rice a day; the Americans, wheat and corn flakes with milk; and the Italians, pasta. All of them were more influenced by the cultural and dietary habits of their countries than by the scientific knowledge . Unfortunately, even today sports nutrition remains the Cinderella of training programs. In spite of the efforts to improve the training of the professionals related to sport, and of the extensive information stored in books and magazines, the sports nutrition is an insufficiently known subject .