2.3 - Balanced Diet

The nutrient groups and their functions

• A balanced diet supplies all the essential nutrients the body needs, in the right proportions.
• There are several groups of nutrients, and because each has its own job, a healthy diet must include all of them in suitable amounts.

The seven nutrient groups

1. Carbohydrates - Found in pasta, rice, bread and sugar. They are the body's main source of energy.
2. Lipids (fats and oils) - Found in butter and oily fish. They provide energy, act as an energy store, insulate the body against heat loss, and protect the internal organs.
3. Proteins - Found in meat, fish and beans. Needed for the growth and repair of body tissue, and can also provide energy in emergencies.
4. Water - From food and drink. Needed for almost every process in the body; a constant supply replaces water lost in urine, in breathing and in sweat.
5. Dietary fibre (roughage) - Found in wholemeal bread and fruit. Not digested, but provides bulk that helps food move through the gut and keeps the digestive system working properly.
6. Vitamins - Needed in small amounts.
   • Vitamin A - From foods such as liver. Helps keep the eyes, skin and hair healthy.
   • Vitamin C - From fruit such as oranges. Needed for healthy tissue and the repair of body tissue.
   • Vitamin D - From eggs and oily fish. Needed so the body can absorb calcium; also made by the skin when exposed to sunlight.
7. Mineral ions - Needed in small amounts.
   • Calcium - From foods such as milk and cheese. Needed to make strong bones and teeth.
   • Iron - From foods such as red meat. Needed to make haemoglobin, the substance in red blood cells that carries oxygen.

How energy needs vary

The amount of energy a person needs from food is not fixed - it differs from person to person and changes over a lifetime.

Factors affecting energy needs

• Activity level - An active person, such as someone doing heavy physical work or lots of exercise, uses up much more energy than someone who is mostly inactive, so they need to take in more energy from their food.
• Age - Children and teenagers need plenty of energy because they are growing and are usually very active, while older, less active people need less.
• Pregnancy - A pregnant woman needs more energy than usual, because she has to supply the energy the developing baby needs to grow as well as meeting her own needs.