Nutrition

5.1.1 Nutrition

Food is essential for survival. Food refers to any substance that nourishes the body — in other words, anything we can digest, absorb and utilise for the body's various physiological functions, including growth and development. From the time of conception in the mother's womb, food plays an enormous role: providing energy for our sustenance, regulating the activities of the body, and repairing the day-to-day wear and tear of its tissues.

Food provides nutrition to the body. Nutrition is the science of food — the study of everything that happens to food from the time it is eaten until it is used for the body's various functions. It is the scientific study of foods and the nutrients they contain: their action, interaction and balance, in health and in disease. More fully, nutrition is the study of the ingestion, digestion, absorption, utilisation and assimilation of the nutrients present in food.

When we look at a food we recognise it as a chapatti, rice, dhal, ladyfinger or apple. But as the food enters the mouth it begins to break down, and the body identifies it by the different chemicals it contains. These chemical substances present in food are called nutrients. The nutrients of physiological importance are carbohydrates, proteins, fats, vitamins, minerals, water and fibre (roughage). Different foods contain these nutrients in different amounts and proportions, and the body needs each nutrient in a specific amount for its various physiological functions and for overall growth and development. In short, nutrients are the chemical substances in food that the body requires for energy, growth and maintenance.

Nutrition therefore operates through several linked stages, and it helps to think of them in order:

• Ingestion — the actual act of eating or drinking the food.
• Digestion — breaking large food molecules down into smaller absorbable units, such as starch into glucose or protein into amino acids.
• Absorption — the broken-down nutrients crossing the gut wall into the bloodstream.
• Utilisation (metabolism) — the body using the absorbed nutrients for energy production, building tissue or driving chemical reactions.
• Assimilation — the incorporation of nutrients into the body's own cells and structures. …