Food function and structure – introduction
We all eat food because it provides the fundamental types of materials required to keep our bodies functioning.
Selection of foods
We need energy to enable growth and repair of tissues, to maintain body temperature and to fuel physical activity. Energy comes from foods rich in carbohydrate, protein and fat.
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
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
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.
Student activities include Iodised salt, Is all salt the same?, Iron content of foods and Vitamin C and the future.
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.
Students watch AgResearch’s Dr Matthew Barnett, the singing scientist, and answer sets of questions and complete activities in the activity I love fibre.
Water
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.
Students quantitatively analyse carrot and banana for moisture content and total solids using and comparing two drying methods in the activity Water content of foods.
Phytochemicals – plants’ chemical treasure trove
Dr David Stevenson defines the term phytochemical and explains some of the actions a class of phytochemicals called polyphenols have within the plant. These range from serving as signalling molecules to boosting the plant’s defence mechanisms in warding off attack from bacterial and fungal pathogens as well as insects that use the plant as a food source.
Phytochemicals
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.
Food colouring
The student activity, Food colouring, uses a simple paper chromatography method to separate and identify the components present in commercially available food colouring. Students investigate the food additive numbering system and research some reported effects colour additives have on children's behaviour.
Question bank
The Food function and structure – question bank provides an initial list of questions about the macronutrients and micronutrients our bodies need and places where their answers can be found. The questions support an inquiry approach.
Key terms
For explanations of key concepts, see Food function and structure – key terms.
Timeline
This timeline traces the history of scurvy, the discovery of a cure for the disease and the isolation and identification of ascorbic acid known also as vitamin C.
