CCEA A-Level Nutrition and Food Science Principles of Nutrition: a complete overview of macronutrients, micronutrients, energy and life-stage needs

What this unit demands

Principles of Nutrition is the chemical and nutritional foundation of CCEA A-Level Nutrition and Food Science. Everything that follows, from diet-related disease to food safety and consumer choice, rests on knowing what each nutrient is, what it does, where it comes from, and what happens when intake is wrong. The examiners test two linked skills: precise recall of nutrients, functions, sources and recommendations, and the ability to apply that knowledge to real diets and to the different stages of life.

This guide walks through the seven dot points of the unit, then sets out the exam patterns CCEA repeats. Each topic has a matching dot-point page with practice questions; this overview ties them together.

The macronutrients

Protein is built from amino acids; the essential ones must come from food, and high biological value proteins (animal sources plus soya) supply them all, while complementing low biological value plant proteins gives a complete supply. Fats and lipids are triglycerides of glycerol and three fatty acids; saturated fats raise blood cholesterol while unsaturated and essential fatty acids support health, and fat is the most energy-dense nutrient at about 37 kJ per gram. Carbohydrates range from simple sugars to starch and dietary fibre; the advice is to base meals on starchy carbohydrates, cut free sugars below 5 percent of energy, and eat about 30 g of fibre a day.

The micronutrients and water

Vitamins are split into the fat-soluble group (A, D, E, K), which is stored and can be toxic in excess, and the water-soluble group (B vitamins and C), which is not stored, is needed regularly and is easily lost in cooking. Minerals such as calcium (bones, with vitamin D needed for absorption), iron (haemoglobin, with vitamin C aiding non-haem absorption) and sodium (fluid balance, but limited to 6 g salt a day) each have specific roles and bioavailability issues. Water makes up about two thirds of body mass and is needed for reactions, transport, temperature control, lubrication and removing waste.

Energy and Dietary Reference Values

Energy balance compares intake with output: a surplus is stored as fat and a deficit causes weight loss. Total energy need is mainly basal metabolic rate plus physical activity, and BMR changes with age, body composition, growth and pregnancy. Dietary Reference Values estimate group needs: the EAR (group average, used for energy), the RNI (enough for nearly everyone, used for nutrients) and the LRNI. The Eatwell Guide turns these into practical food-group proportions.

Nutritional needs through life

Needs change at every stage. Pregnancy demands folate, iron, calcium and vitamin D with only a small energy rise; infancy moves from milk to weaning at around six months; children and adolescents need energy, protein, calcium and iron for growth; adults balance their diet to maintain health; and older adults need less energy but a nutrient-dense diet to protect muscle and bone. The principle throughout is to match energy to need while keeping nutrient quality high.

How this unit is examined

A typical CCEA profile for Principles of Nutrition:

• Recall and structure. Naming nutrients, their building blocks, functions and food sources, and stating the key recommendations.
• Explanation. Linking nutrient structure to function, explaining biological value and bioavailability, and explaining energy balance and the DRV terms.
• Data and calculation. Working out energy balance, free-sugar limits and protein needs, and interpreting nutrition labels.
• Application. Adapting diets to the life stages and judging the adequacy of a given diet against the Eatwell Guide and DRVs.

Check your knowledge

A mix of recall and explanation questions covering the unit. Attempt them under timed conditions, then check against the solutions.

1. Explain the difference between a high and a low biological value protein. (2 marks)
2. State the energy value, in kJ per gram, of fat, carbohydrate and protein. (3 marks)
3. Explain why unsaturated fats are usually liquid at room temperature. (2 marks)
4. Define a free sugar and state the recommended maximum as a percentage of food energy. (2 marks)
5. Explain why vitamin D is needed for calcium in the diet. (2 marks)
6. Explain the difference between the EAR and the RNI. (2 marks)
7. State two ways to reduce the loss of vitamin C when cooking vegetables. (2 marks)
8. Explain why a pregnant woman needs extra iron. (2 marks)