Balanced diet — every nutrient type, in the right amount
A balanced diet contains all the nutrient types the body needs, in the amounts needed to stay healthy: carbohydrate, fat/oil, protein, vitamins (C and D), the mineral ions calcium and iron, fibre and water. How much of each a person needs varies with age, activity level, health and whether they are pregnant. A diet missing one type — or carrying far too much or too little of one — is not balanced, even when it supplies plenty of energy.
Energy nutrients vs the building nutrient
Carbohydrate (bread, rice, pasta, potatoes, sugar) is the body's main energy source. Fat/oil (butter, cooking oil, oily fish, dairy products) is also an energy source, and additionally gives insulation and protects organs. Protein (meat, fish, eggs, beans, dairy products) is needed for the growth and repair of body tissues — cells and tissues are largely built from protein, so its role is structural rather than energy-supplying.
Vitamins, mineral ions, fibre and water
Vitamin C (citrus fruits) keeps skin, gums and connective tissue healthy; a lack causes scurvy. Vitamin D (dairy products, oily fish, also made in skin in sunlight) lets the body absorb calcium; a lack causes rickets. Calcium (dairy, green leafy vegetables) gives strong bones and teeth. Iron (red meat, liver, leafy greens) makes haemoglobin; a lack causes anaemia. Fibre prevents constipation; water is the solvent for the body's reactions and replaces losses from sweating.
Drawn from real examiner reports.
Fibre ≠ growth or strong bones
Fibre (roughage) is indigestible plant material — mainly cellulose from plant cell walls — that adds bulk to food in the gut and stimulates the gut-wall muscles (peristalsis). Its one credited importance is that it prevents constipation. Borrowing protein's answer ("needed for growth") or calcium's answer ("strong bones") scores nothing on a fibre question.
Flagged Nov 2022 P31 Q1biii
Iron makes haemoglobin, not bone
Calcium and iron are both mineral ions on the B7.1 list and their roles are routinely swapped. Calcium is needed for strong bones and teeth. Iron is needed to make haemoglobin, the oxygen-carrying molecule in red blood cells; a shortage causes anaemia and tiredness. Iron has no role in bone strength on this specification, so "iron strengthens bones" earns nothing.
Flagged Jun 2023 P31 Q1c
Vitamin C and vitamin D get swapped
Learn two fixed pairings separately: C for citrus, C for scurvy; D for dairy/oily fish/daylight on skin, D for rickets. Naming citrus fruit as a vitamin D source, or scurvy as the vitamin D deficiency, loses the source mark and the disease mark. Rickets shows as soft, deformed bones in growing children.
Protein is for growth, not energy
Carbohydrate and fat/oil are the two energy nutrients; protein is the structural one. When a question asks for the importance of protein, the credited answer is growth and repair of body tissues. Answering "energy" describes what carbohydrate and fat do and does not earn the protein mark, even though protein can be respired.
Balanced ≠ eating enough food
A diet can supply plenty of energy and still be unbalanced. Rice, fried chicken, cola and chocolate deliver ample carbohydrate and fat/oil while supplying no vitamin C, vitamin D, calcium, iron or fibre. Balance means every nutrient type is present in the amount needed — not that the total energy intake is sufficient.
Vitamin D does not itself build bone
Calcium is the bone material; vitamin D is what lets the body absorb calcium from food. So rickets is a calcium-absorption failure, not a shortage of calcium in the diet — bones can stay soft even when calcium is being eaten. Explain questions want that chain, not the bare statement that a lack of vitamin D causes rickets.
Use the source → importance → deficiency scaffold
Answer every nutrient question the same way: name a specific food, state the short-phrase function, then give the named deficiency where the specification has one. Vitamin C → scurvy; vitamin D → rickets; iron → anaemia; calcium → weak bones and teeth.
Name a food, not a food group
Vague categories are not credited. Write "citrus fruits", not "fruit"; "dairy products" or "oily fish", not "food"; "red meat" or "liver", not "meat". One precisely named source scores where a list of loose categories does not.
Food-diary questions: name what is missing
Work through all seven nutrient categories in turn and check each against the foods listed. Then name the specific nutrients that are absent, and the food that would supply each one. Answering only "the diet is not balanced", with no nutrient named, gains no marks.
State vs explain on deficiency questions
"State what causes rickets" wants one fact: a lack of vitamin D. "Explain how a lack of vitamin D leads to rickets" wants the whole chain — poor calcium absorption, bones not mineralising, soft and deformed bones. Read the command word before deciding how much mechanism to write.
Cambridge 0654 spec reference: Section B7 "Human nutrition", sub-topic B7.1 (Core only in this leaf -- no Supplement/Extended detail). This leaf covers describing a balanced diet; the principal dietary sources and importance of carbohydrates, fats/oils, proteins, vitamin C, vitamin D, the mineral ions calcium and iron, fibre (roughage) and water; and the causes of scurvy and rickets.
Balanced diet -- a diet that contains all the different nutrient types (carbohydrate, fat/oil, protein, vitamins, mineral ions, fibre, water) in the amounts needed to keep the body healthy.
Scurvy -- a deficiency disease caused by a lack of vitamin C in the diet.
Rickets -- a deficiency disease caused by a lack of vitamin D in the diet, resulting in soft or deformed bones (most often seen in growing children).
Fibre (roughage) -- indigestible plant material (mainly cellulose from plant cell walls) that adds bulk to food in the gut and stimulates the muscles of the gut wall, preventing constipation.
Define "balanced diet".
(a) Describe what is meant by a "balanced diet". (2 marks)
(b) List FOUR different nutrient types (other than water) that must be present in a balanced diet. (4 marks)
