Jane Griffin - Nutrition for Marathon Running

Food provides the body with the energy and nutrients it needs for growth and development, to meet daily lifestyle requirements and maintain health. Food choices making up a runners daily diet must meet all these requirements, otherwise running performance will suffer, risk of infection and injury will increase, and there may even be long-term health implications. Not only do nutrients perform different functions in the body but the type and amount of nutrients varies from food to food. Understanding what energy and nutrients do in the body and which foods are good sources of particular nutrients will help a runner to build up the best possible diet. That diet should maximize performance, both in training and races, and keep the body fit and healthy. It must also be practical and fit into the lifestyle and daily schedule of the runner and of course it must be enjoyable!

Food is made up of carbohydrate, fat, protein , vitamins, minerals and water. In some foods, particularly fruits and vegetables, a very large proportion is water; in others, such as oils and fats, the water content is minimal. The amounts and indeed the presence of the different vitamins and minerals can vary considerably between foods, too. This is one of the reasons why health professionals are constantly encouraging the general public to eat a diet containing a wide variety of different foods.

Carbohydrate and fat are the major sources of energy or fuel for the body. Protein has the unique function of providing the material for the growth and repair of the body and is also an important component of enzymes, hormones and antibodies. When the diet contains more protein than is needed it contributes to the overall energy pool of the body. If insufficient carbohydrates and fats are available to meet energy demands, protein can be used to meet the shortfall.

Vitamins and minerals are essential components of the diet. Although the majority of them are needed in very small amounts they do play vital and often very different roles in the diet. Vitamins are a diverse group of substances that are needed for the regulation of chemical processes in the body. Although not a source of energy in themselves, many of them are involved in the release of energy from food. They cannot be made in the body in sufficient amounts to meet requirements and so must be provided by the diet. Minerals are also essential nutrients, which must be supplied by the diet. Like vitamins, they fulfil many functions. They help to control the composition of body fluids, and are constituents of bones and teeth and essential components of enzymes and proteins such as haemoglobin.

It is a myth that energy is good because it helps to fuel activities such as running and calories are bad because they are fattening. In that case, an energy bar will help a runner but a chocolate bar will make him or her fat! Energy can be measured in calories or joules. For the scientifically minded, one calorie is the amount of heat needed to raise the temperature of 1g of water by 1C. The calorie is a very small unit, so the Calorie, which is 1,000 times greater than the calorie, has always been used for nutritional measurements . The kilocalorie is the same as the Calorie. This avoids any confusion between calorie and Calorie (initial capital C) and the possibility of printing errors on food packaging. Kilocalories have been replaced by the general unit for measuring energy, the kilojoule. Although it is more scientifically correct to use kilojoules, kilocalories still remains popular with the general public and both units are used in food labelling.