Nutrition is a biological process when food constituents are turned into body tissues and energy for various kinds of activity is provided.
How food energy is supplied
The body gets energy from digested foods. This energy is used for muscular work and metabolic activity to keep the body construction and functions in order. These processes are inseparable from heat production. Heat exchange is controlled by particular mechanisms to maintain body temperature within normal range. The organism is constantly destroying and manufacturing its own constituents. Foods provide nutritive substances required for building new materials and covering energetic needed for chemical reactions.
Units of energy
Carbohydrate, fat, and protein serve as sources of satisfying energetic necessities. Food energy is measured in Calories. Another unit of energy measure is the joule. The joule measures the energy from the standpoint of mechanical activity. 1 Calorie is equal to 4.184 kilojoules.
How the energy is measured
Food energy can be detected by means of measuring heat produced by burning various foods. Energy values for 1 gram are: carbohydrate-4 Calories (17 kilojoules); protein - 4 Calories (17 kilojoules); and fat - 9 Calories (38 kilojoules). Vitamins, minerals, and water do not produce energy. However, they may take part in energy releasing. Food energy can be calculated knowing the amounts of nutritional constituents. Foods are usually mixed sources of energy. However, sugar and vegetable oil are pure carbohydrate and fat sources.
Relationships between energy sources in diets
Usually about 12 - 15 % of energy is taken from protein, 30 - 40 % from fat, and 50 - 60 % from carbohydrate. The body can adapt to different diets and nutrient combinations. However, different dietary approaches may be associated with various health consequences.
Health consequences of wrong nutrition
Nutritional diseases may develop from under- or over-nutrition.
Obesity results from excessive caloric consumption. Obesity may lead to serious medical conditions such as chronic oxygen deficiency, hypertension, atherosclerosis, and vascular degeneration. Excessive consumption of fat soluble vitamins can end in their amassing to toxic levels in cells and tissues.
Protein and caloric malnutrition develop if the quantity and quality of food are insufficient. Protein malnutrition results in significant weight loss leading to infections with gastrointestinal bacteria and parasites.
Vitamin deficiencies develop against the background of inadequate diets. Vitamin deficiencies also arise as a result of disturbed vitamin absorption or increased vitamin loss. Vitamin deficiencies are possible during rapid growth of children, teenagers and in pregnancy when the requirements in nutrients are increased.
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