Diet and nutrients

Last time

Before we start: last time, in Digestive enzymes and absorption in the villi, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

You are what you eat

Sailors on long voyages once died of scurvy, until they were given lemons and limes. A balanced diet must contain the right nutrients in the right amounts. Today: the seven parts of a balanced diet, what each does, and what happens when one is missing.

A balanced diet

A balanced diet contains all the nutrients in the correct proportions, plus enough energy for the person's needs. The seven parts are carbohydrates, fats and oils, proteins, vitamins, mineral ions, dietary fibre and water.

The energy nutrients

Carbohydrates, found in rice, bread and potatoes, are the main source of energy. Fats and oils, in butter and nuts, store energy and insulate the body. Proteins, in meat, fish, eggs and lentils, are used for growth and repair of cells.

Vitamins

Vitamin C, from citrus fruit, is needed to make collagen for skin and gums. A lack causes scurvy: bleeding gums. Vitamin D, from oily fish and egg yolk and made in skin in sunlight, helps absorb calcium. A lack causes rickets: soft, bent bones.

Mineral ions

Calcium, from milk and cheese, makes strong bones and teeth. Iron, from red meat and spinach, is needed to make haemoglobin in red blood cells. A lack of iron causes anaemia: tiredness, because the blood carries less oxygen.

Fibre and water

Dietary fibre, from vegetables and wholemeal bread, cannot be digested. It gives bulk to the food, so the gut muscles can push it along. This prevents constipation. Water is needed for all chemical reactions, for transport in blood, and to remove waste.

The diet table

Here is the table to learn. Each nutrient, a source, its use, and what happens if it is missing. The examiner often names the disease and asks for the nutrient.

Needs vary

An active teenager, still growing, needs more energy and protein than an elderly person. A pregnant woman needs extra iron and calcium for the baby's blood and bones. A manual worker needs more energy than an office worker.