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The Make Up of a Polar Diet
A nutritious diet is not just about having an abundant source of food; it is about having a diet that is balanced. Today thanks to the science of nutrition we know a balanced diet involves a combination of carbohydrates, fats, proteins, fibre, vitamins, minerals (plus water) in varying amounts to remain healthy.
Carbohydrates: these are a major source of the body’s energy as they supply energy in a form which the body finds easy to metabolise. The body’s enzymes are able to break down carbohydrates into digestible sugars. Any excess sugars can be stored as fat and kept as reserves, when low on energy the body can convert these fat stores to sugar to use as energy. This will result in weight loss; many of the photographs depict how people at the poles tend to lose weight during their expedition as their fat reserves are burnt up. In addition carbohydrates regulate protein and fat metabolism, and are necessary to breakdown fat within the liver. For a person on a polar expedition it is recommended that carbohydrates make up 50% of their daily calorie intake.
Fats: these are key resources, especially in cold climates as they are an extremely concentrated energy supply. However, fats are much harder to break down than carbohydrates, requiring five times the amount of energy. In addition fat is required to absorb the fat soluble vitamins A, D, E and K. During a polar expedition fats should make up 25-30% of the daily calorie intake.
Proteins: are used by the body as a sustained source of heat and energy, this is especially important in the polar climate. Protein is a source of building material in the body, and is essential for the regulation of the blood clotting mechanism. Protein should only be used by the body as an energy source if sufficient energy is not available from fats and carbohydrates. Excess protein can be converted by the liver and stored as fat in the body. When protein is digested this results in the production of amino acids which the body uses as building blocks. For a person on a polar expedition proteins should make up 20-25% of the daily calorie intake.
Minerals: these must be supplied by a person’s diet as the body is unable to produce them but they are vital in the metabolic processes of the body. A diet that has enough protein and energy should be sufficient in minerals, however, this is not always the case on long polar expeditions and so today a supplement is recommended.
Vitamins: In most cases the body is unable to produce vitamins and so it needs to get them from the diet. If a person is eating a balanced diet these should be available and so it should not be necessary to take a vitamin supplement. On long expeditions when the diet is poorly balanced and lacking in fresh foods vitamin deficiencies are common. The lack of vitamin C in particular has had a major effect on the outcome of many expeditions. In addition explorers have been know to overdose on Vitamin A (hypervitaminosis) through eating bear and dog liver which is very high in Vitamin A. Today it is recommended that vitamin supplements are taken to counteract any problems caused by poor diet.
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