Nutrition is the study of how food affects the body: how it is digested, absorbed and used to sustain growth, repair and activity.
Macronutrients
- Carbohydrates — the body's primary energy source. Whole grains, legumes, fruit and vegetables also supply fibre, which supports digestion and slows the release of sugar into the blood.
- Proteins — supply amino acids for building and repairing tissue. Found in meat, fish, eggs, dairy, legumes and nuts.
- Fats — necessary for hormone production and absorption of certain vitamins. Unsaturated sources such as vegetable oils, nuts and fish are generally preferable to large amounts of saturated fat.
Micronutrients
Vitamins and minerals are required in small quantities but are essential. Deficiencies with wide public-health significance include iron, iodine, vitamin D and vitamin A. A varied diet is the most reliable way to cover them; supplements address specific, diagnosed gaps.
Water
Water regulates temperature, transports nutrients and removes waste. Needs vary with climate, body size and activity level, and rise significantly in hot weather or during physical work.
Practical principles
Most credible dietary guidance converges on a few points:
- eat a variety of foods, with plenty of vegetables, fruit and whole grains;
- limit added sugar, salt and heavily processed products;
- match energy intake to activity level;
- keep meal patterns reasonably regular;
- treat extreme or highly restrictive diets with caution.
A note on claims
Nutrition is a field where marketing frequently outruns evidence. Claims about a single food curing a condition, or eliminating an entire food group for everyone, deserve scepticism. Individual needs differ, and medical conditions change what is appropriate — a qualified professional should advise in those cases.