The three nutrients required in the largest quantities are:
Other nutrients required in smaller quantities are:
To obtain these nutrients humans, as omnivores, eat a varied diet.
Here are the sources and main functions of the different components in a balanced diet.
Vitamins are only needed in small amounts to maintain a healthy body. A lack of vitamins in the diet leads to deficiency symptoms.
Vitamin C (ascorbic acid) is needed to help heal wounds and maintain healthy connective tissue (which gives support to other tissues and organs).
Good sources of vitamin C include:
Vitamin C deficiency leads to scurvy. The symptoms of scurvy include bleeding and swelling of the gums, loss of teeth, tiredness and muscle and joint pain.
Like vitamins, mineral ions are only needed in small amounts to maintain a healthy body. A lack of the correct mineral ions in the diet also leads to deficiency symptoms.
Iron is needed to produce haemoglobin, found in red blood cells.
Good sources of iron include:
Iron deficiency causes anaemia. People with anaemia become tired and weak because their blood does not transport enough oxygen.
Water and dietary fibre (roughage) are also important components in the diet.
About two-thirds of the human body is water. It is found in the cytoplasm of our cells and in body fluids like blood.
Sources of water include:
Dietary fibre consists of material in food that cannot be digested, in particular cellulose from plant cell walls.
Sources of fibre include:
Dietary fibre is important because it provides bulk, which helps the walls of the intestine move food and faeces along the gut. Lack of dietary fibre can lead to constipation.