7.1.1B4. Human Nutrition and Digestion

Diet and Deficiencies — Combined Science 0653 - Biology Revision Notes & Topical Questions

5 min read 6 parts Lesson 5 of 6 Unit quiz

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Part 1 of 4The components of a balanced diet

Food group	Main role in the body	Example sources
Carbohydrates	The main source of energy for respiration	Bread, rice, potatoes, pasta
Proteins	Growth and repair of tissues; making enzymes and hormones	Meat, fish, eggs, beans
Lipids (fats and oils)	Energy store, insulation and part of cell membranes	Butter, oils, nuts, oily fish
Vitamins	Needed in small amounts to keep the body working properly	Fruit, vegetables, dairy foods
Minerals	Needed in small amounts, for example calcium for bones and iron for blood	Milk, green vegetables, red meat
Dietary fibre	Provides bulk so food moves along the gut and prevents constipation	Wholegrain cereals, vegetables, fruit
Water	Solvent for reactions, transport medium in blood, and needed for cooling	Drinks and most foods

Age

Age Growing children need extra protein and calcium to build tissues and bones.

Activity level

Activity level People with active lifestyles or physically demanding jobs use more energy and so need more carbohydrate and lipid.

Pregnancy and breastfeeding

Pregnancy and breastfeeding A mother needs extra protein, calcium and iron to support the baby's development and to produce milk.

Sex and body size

Sex and body size Larger people and people with more muscle generally need more energy,
- and iron needs differ because of blood loss during menstruation.

1Lack of vitamin C

Lack of vitamin C Little or no vitamin C is eaten for more than about three months, because fresh fruit and vegetables are missing from the diet.

2Tissues weaken

Tissues weaken Vitamin C is needed to keep skin, gums and blood vessels healthy, so these begin to break down.

3Symptoms appear

Symptoms appear Anaemia, tiredness, bleeding without injury, painful limbs, swelling, ulcerated gums and loss of teeth.

4Treatment

Treatment Vitamin C supplements, taken by mouth or given into a vein, together with fresh fruit and vegetables.
- Sailors on long voyages often suffered from the disease in past centuries.

Rickets: poor bone development in children

Cause

Cause A severe lack of vitamin D, which the body needs to absorb calcium from food.

Why calcium matters

Why calcium matters Calcium is a key mineral in bones and teeth, so without it the bones stay soft and weak.

Symptoms

Symptoms Bone pain, slow growth and soft bones that bend under the body's weight, causing deformities such as bowed legs.

Sources of vitamin D

Sources of vitamin D Skin makes much of it when exposed to sunlight;
- oily fish, eggs and butter also supply some.

Treatment

Treatment Eat more foods rich in calcium and vitamin D, or take vitamin D supplements prescribed by a doctor.

Term	Meaning
Balanced diet	A diet containing all the food groups in the correct proportions for the person's needs.
Deficiency disease	An illness caused by a lack of a particular nutrient in the diet.
Vitamin C	A vitamin found in citrus fruits and vegetables that keeps skin, gums and blood vessels healthy.
Vitamin D	A vitamin that helps the body absorb calcium; made in skin in sunlight.
Dietary fibre	Plant material that cannot be digested and helps food move through the gut.
Scurvy	A disease caused by a long-term lack of vitamin C.

Saying rickets is caused by a lack of calcium alone. The cause is a lack of vitamin D, which stops calcium being absorbed.

Thinking fibre provides energy or nutrients. Fibre cannot be digested; its role is to add bulk to the food in the gut.

Claiming everyone needs the same diet. Age, activity and pregnancy all change nutrient requirements.

Mixing up scurvy (vitamin C) and rickets (vitamin D) or their symptoms.

Last updated: 20 October 2026