We all eat food because it provides the fundamental types of materials required to keep our bodies functioning.

These materials can be categorised as:

  • macronutrients – carbohydrates, proteins, fats and oils
  • micronutrients – vitamins and minerals
  • dietary fibre – cellulose, pectin and gums
  • dietary water – keeping the body hydrated
  • phytochemicals – biologically active compounds from fruits and vegetables.

It has been estimated that an average person consumes 25 tonnes of food within their lifetime, and most of that food sits in the macronutrient category.

Macronutrients are required in large amounts to provide the energy needed to maintain body functions and carry out the activities of daily life. There are three macronutrients – carbohydrates, proteins and fats.

Find out why we need carbohydrates, proteins and fats in our diet as well as the structure and function of these macronutrients.

Micronutrients are substances such as vitamins and minerals that are necessary dietary components. Although needed in only small amounts, they are essential for health and wellbeing.

We look at what vitamins and minerals are and the role that selected examples play in keeping the body in a healthy state, in particular, vitamin C.

Dietary fibre
Dietary fibre is that portion of the food we eat that is resistant to digestion and absorption in the small intestine. Fibre is found in fruits, vegetables, nuts and grains and is an important ingredient of a healthy diet.

Find out about the types of fibre found in the diet and the function of fibre in the body.

Dietary water is the most abundant and most frequently overlooked component of food. The water content of solid foods makes a considerable contribution to our total water intake.

We look at daily water requirements, water’s solvent and transport properties and the critical role water plays in breaking large food molecules into smaller molecules.

Phytochemicals are biologically active compounds that are found in small amounts in fruits and vegetables. These compounds contribute to human health because they might help protect against degenerative diseases such as cancer

Find out how phytochemicals are classified, how they work in the body, and why they should be included in a healthy diet, as well as the antioxidant capacity of certain types of phytochemicals.

Functional foods
Functional foods are similar to conventional foods that form part of a normal diet – the difference is that they have a demonstrated positive benefit to overall health as well as the potential to reduce the risk of chronic diseases. We look at examples of functional foods and the increasingly important role they could play in our diets in the future and meet some of the scientists involved.

Key terms

For explanations of key concepts, see Food function and structure – key terms.

    Published 18 March 2011