Nutrition is defined as the intake of food, considered in relation to the body's dietary needs. Good nutrition - an adequate, well balanced diet combined with regular physical activity - is a cornerstone of good health. Poor nutrition can lead to reduced immunity, increased susceptibility to disease, impaired physical and mental development, and reduced productivity. The diet of an organism is what it eats, which is largely determined by the availability, processing and palatability of foods. A healthy diet includes preparation of food and storage methods that preserve nutrients from oxidation, heat or leaching, and that reduce risk of food-born illnesses.
Eating a healthy nutritious diet has been shown over and over to prevent a variety of diseases, including cancer. Good nutrition is vital to good health, disease prevention, and essential for healthy growth and development of children and adolescents.
There are seven major classes of nutrients: carbohydrates, fats, fiber, minerals, protein, vitamins, and water.
- Carbohydrates - our main source of energy.
- Fats - one source of energy and important in relation to fat soluble vitamins.
- Roughage (Fiber) - the fibrous indigestible portion of our diet essential to health of the digestive system.
- Minerals - those inorganic elements occurring in the body and which are critical to its normal functions.
- Proteins - essential to growth and repair of muscle and other body tissues.
- Vitamins - water and fat soluble vitamins play important roles in many chemical processes in the body.
- Water - essential to normal body function - as a vehicle for carrying other nutrients and because 60% of the human body is water.
These nutrient classes can be categorized as either;
- Macro-nutrients (needed in relatively large amounts) - The macro-nutrients are carbohydrates, fats, fiber, proteins, and water.
- Micro-nutrients (needed in smaller quantities) - The micro-nutrients are minerals and vitamins.
The macro-nutrients (excluding fiber and water) provide energy, which is measured in Joules or kilo-calories (often just called Calories).
Carbohydrates and proteins provide 17 kJ (4 kcal) of energy per gram, while fats provide 37 kJ (9 kcal) per gram.
Vitamins, minerals, fiber, and water do not provide energy, but are necessary for other reasons.
The human body contains chemical compounds, such as water, carbohydrates (sugar, starch, and fiber), amino acids (in proteins), fatty acids (in lipids), and nucleic acids (DNA and RNA). These compounds in turn consist of elements such as carbon, hydrogen, oxygen, nitrogen, phosphorus, calcium, iron, zinc, magnesium, manganese, and so on. All of these chemical compounds and elements occur in various forms and combinations (e.g. hormones, vitamins, phospholipids, hydroxyapatite), both in the human body and in the plant and animal organisms that humans eat.
Water is one of the most important nutrients in your diet. It helps eliminate food waste products in your body, regulates body temperature during activity, and helps digest food.
Most fatty acids are non-essential, meaning the body can produce them as needed. However, in humans at least two fatty acids are essential and must be included in the diet. An appropriate balance of essential fatty acids, Omega-3 and omega-6 fatty acids, is important for health. Both of these "omega" long-chain polyunsaturated fatty acids are substrates for a class of eicosanoids known as prostaglandins, which have roles throughout the human body.