Pearson Edexcel International GCSE Human Biology 6: Nutrition and energy

Nutrition supplies substrates for energy release, raw materials for growth and repair, and micronutrients needed for normal physiology. Pearson Edexcel International GCSE Human Biology (4HB1) Topic 6 connects a balanced diet to digestion, absorption, teeth, deficiency disease, body mass index and food hygiene. Energy release itself belongs to Topic 7 Respiration.

1. A balanced diet

A balanced diet provides appropriate proportions and quantities of nutrients, energy and fibre for an individual. It is not one fixed menu. Recommended intake varies with age, pregnancy, climate, activity and occupation. A growing adolescent needs materials for new tissue; pregnancy increases several nutrient demands; physical work raises energy expenditure; and temperature can change energy use and fluid loss.

Carbohydrates are important respiratory substrates. Sources include cereals, rice, bread, potatoes and fruit. Proteins provide amino acids for growth, repair, enzymes, antibodies and some hormones; sources include meat, fish, eggs, dairy products, beans and lentils. Lipids provide concentrated energy, insulation, protection and membrane components; sources include oils, nuts, seeds, dairy products and fatty foods.

Vitamin A supports vision and healthy epithelia, and occurs in liver, dairy foods and carotene-rich vegetables. Vitamin C supports collagen formation and wound healing, and occurs in many fruits and vegetables. Vitamin D supports calcium absorption and bone mineralization and can come from diet and synthesis in skin exposed to sunlight. Calcium supports bones, teeth, muscle and nerve function. Iron is needed to make haemoglobin. Dietary fibre adds bulk, retains water and supports movement through the gut.

Recommended intake is a population guide, not proof that every individual has identical needs. Energy intake and expenditure also need to be considered over time.

2. Deficiency diseases

Deficiency occurs when intake, absorption or use of a nutrient is inadequate for long enough to impair function.

• Vitamin C deficiency causes scurvy, with weak connective tissue, bleeding gums and poor wound healing.
• Iron deficiency can cause anaemia because less haemoglobin is produced. Symptoms may include fatigue, pallor and breathlessness.
• Vitamin A deficiency can impair vision and may lead to blindness, especially through damage associated with severe deficiency.
• Severe protein deficiency can cause kwashiorkor, characterized by impaired growth, muscle wasting and oedema.

Symptoms are not unique diagnoses. Fatigue, for example, has many possible causes. Examination answers should connect a named deficiency to the disrupted biological role.