What you'll learn
This revision guide covers all testable content on Nutrition for CXC CSEC Integrated Science. You'll master the six main nutrient groups, their functions and sources, understand balanced diets and dietary requirements, and learn to identify deficiency diseases. The content aligns directly with the CXC syllabus and includes Caribbean-specific examples.
Key terms and definitions
Nutrition — the process by which organisms obtain and use food substances for growth, repair, energy and maintenance of life processes
Nutrient — a chemical substance found in food that performs specific functions in the body
Balanced diet — a diet containing all six nutrient groups in the correct proportions to maintain good health
Malnutrition — a condition resulting from an unbalanced diet, either from excess or deficiency of nutrients
Deficiency disease — an illness caused by the lack of a specific nutrient in the diet over a prolonged period
Macronutrients — nutrients required in large amounts (carbohydrates, proteins, fats)
Micronutrients — nutrients required in small amounts (vitamins, minerals)
Metabolic rate — the rate at which chemical reactions occur in body cells to release energy
Core concepts
The six nutrient groups
The human diet must contain six main nutrient groups, each with specific functions:
Carbohydrates
- Main function: provide energy for cell respiration
- Two types: simple sugars (glucose, sucrose) and complex carbohydrates (starch, cellulose)
- Caribbean sources: cassava, dasheen, yam, sweet potato, breadfruit, rice, green bananas, plantains
- Excess stored as glycogen in liver and muscles, or converted to fat
Proteins
- Main functions: growth, repair of tissues, making enzymes and antibodies
- Composed of amino acids; humans need 20 types, 8 are essential (must come from diet)
- Complete proteins contain all essential amino acids; incomplete proteins lack some
- Caribbean sources: red beans, pigeon peas, saltfish, chicken, eggs, milk, cheese
- Animal proteins typically complete; plant proteins often incomplete
- Used for energy only when carbohydrates and fats are depleted
Fats (Lipids)
- Main functions: concentrated energy source, insulation, protection of organs, making cell membranes
- Provide twice the energy per gram compared to carbohydrates
- Two types: saturated (solid at room temperature) and unsaturated (liquid at room temperature)
- Caribbean sources: coconut oil, avocado, butter, vegetable oils, nuts
- Excess stored under skin and around organs
Vitamins
- Required in small amounts for specific body functions
- Two categories: fat-soluble (A, D, E, K) and water-soluble (B, C)
Key vitamins for CSEC:
| Vitamin | Function | Sources | Deficiency disease |
|---|---|---|---|
| A | Good vision, healthy skin | Carrots, liver, milk, eggs | Night blindness, dry skin |
| C | Healthy gums and skin, wound healing, iron absorption | Citrus fruits, tomatoes, guava, West Indian cherry | Scurvy (bleeding gums, poor healing) |
| D | Calcium absorption for strong bones and teeth | Sunlight on skin, fish oils, fortified milk | Rickets (in children), osteomalacia (in adults) |
Minerals
- Inorganic elements needed for body functions
Key minerals for CSEC:
| Mineral | Function | Sources | Deficiency disease |
|---|---|---|---|
| Calcium | Strong bones and teeth, blood clotting, muscle contraction | Milk, cheese, small fish with bones (sprats) | Rickets, weak bones, tooth decay |
| Iron | Making haemoglobin in red blood cells | Red meat, liver, callaloo, green leafy vegetables | Anaemia (fatigue, pale skin, breathlessness) |
| Iodine | Making thyroxine (controls metabolic rate) | Seafood, iodized salt | Goitre (swollen thyroid gland), reduced metabolic rate |
Water
- Makes up 60-70% of body mass
- Functions: solvent for chemical reactions, temperature regulation, transport medium in blood, removal of waste
- Caribbean sources: drinking water, coconut water, fruit juices, soups
- Loss through urine, sweat, breathing, faeces
- Dehydration causes concentrated urine, headaches, reduced performance
Dietary fibre (Roughage)
- Not digested but provides bulk for intestinal movement
- Prevents constipation by stimulating peristalsis
- May reduce risk of bowel cancer and diabetes
- Caribbean sources: whole grain bread, bran, fruits (especially skins), vegetables, peas, beans
Balanced diets and dietary requirements
A balanced diet varies according to:
Age
- Infants and children: high protein for growth; high calcium for bone development
- Adolescents: increased energy for rapid growth; girls need extra iron (menstruation)
- Adults: maintenance levels; pregnant women need extra protein, iron, calcium, vitamin D
- Elderly: less energy (lower activity); calcium and vitamin D for bone health
Activity level
- Manual workers (farmers, construction workers): high carbohydrate and fat for energy
- Office workers: moderate energy requirements
- Athletes: very high carbohydrate for energy; high protein for muscle repair
Climate
- Hot Caribbean climate: increased water requirement due to sweating
- Less need for high-fat diets compared to cold climates
Gender
- Males generally require more energy than females (larger body size, more muscle mass)
- Females need more iron (menstruation) and extra nutrients during pregnancy and lactation
Energy requirements and measurement
Energy in food is measured in kilojoules (kJ) or kilocalories (kcal).
- 1 kcal = 4.2 kJ
Energy values per gram:
- Carbohydrates: 17 kJ/g
- Proteins: 17 kJ/g
- Fats: 38 kJ/g
Daily energy requirements (approximate):
- Adult male (moderate activity): 10,500 kJ
- Adult female (moderate activity): 8,800 kJ
- Adolescent male: 11,500 kJ
- Adolescent female: 9,200 kJ
- Manual labourer: 15,000 kJ
Basal metabolic rate (BMR) is the minimum energy required to maintain life processes at rest (breathing, heartbeat, maintaining body temperature).
Malnutrition and deficiency diseases
Types of malnutrition:
Undernutrition
- Insufficient total food intake
- Results in weight loss, fatigue, weakened immune system
- Starvation: prolonged severe undernutrition
Protein-energy malnutrition (PEM) Two main forms:
Kwashiorkor
- Caused by severe protein deficiency (often after weaning)
- Symptoms: swollen abdomen (fluid retention), thin limbs, reddish hair, flaky skin, poor growth
- Common in developing regions where diet is mainly carbohydrate (cassava, yam)
Marasmus
- Caused by deficiency of both protein and energy
- Symptoms: extreme weight loss, muscle wasting, wrinkled skin, stunted growth
- Child appears "skin and bones"
Obesity
- Excess body fat from consuming more energy than expended
- Health risks: heart disease, diabetes, high blood pressure, joint problems
- Increasing problem in Caribbean due to dietary changes (fast food, processed foods)
Vitamin and mineral deficiencies See tables in "Six nutrient groups" section for specific deficiency diseases.
Food tests
CSEC students must know chemical tests for nutrients:
Test for starch
- Reagent: Iodine solution (brown)
- Positive result: Blue-black colour
Test for reducing sugars (glucose)
- Reagent: Benedict's solution (blue)
- Method: Heat mixture in water bath
- Positive result: Colour changes from blue → green → yellow → orange → brick-red precipitate
Test for protein
- Reagent: Biuret reagent (or sodium hydroxide + copper sulfate)
- Positive result: Violet/purple colour
Test for fats
- Reagent: Ethanol, then add to water
- Positive result: White cloudy emulsion forms
Test for vitamin C
- Reagent: DCPIP (blue dye)
- Positive result: Blue colour decolorizes (turns colourless)
Worked examples
Example 1: Dietary planning (6 marks)
Question: A 15-year-old Caribbean athlete requires a diet to support training. Explain why this person needs: (a) more carbohydrates than an office worker [2 marks] (b) more protein than their younger sibling [2 marks] (c) more water than a person living in a cold climate [2 marks]
Mark scheme answer:
(a) Athletes perform high levels of physical activity [1 mark] which requires more energy from respiration/carbohydrates are the main source of energy [1 mark]
(b) The 15-year-old is still growing/developing [1 mark] and needs protein for growth and repair of muscle tissue damaged during training [1 mark]
(c) The Caribbean has a hot climate [1 mark] which causes increased sweating/water loss that must be replaced to prevent dehydration [1 mark]
Example 2: Identifying deficiency diseases (4 marks)
Question: Match each deficiency disease with its cause:
| Disease | Cause |
|---|---|
| Anaemia | |
| Rickets | |
| Scurvy | |
| Goitre |
Options: lack of vitamin C, lack of calcium/vitamin D, lack of iron, lack of iodine
Answer:
- Anaemia: lack of iron [1 mark]
- Rickets: lack of calcium/vitamin D [1 mark]
- Scurvy: lack of vitamin C [1 mark]
- Goitre: lack of iodine [1 mark]
Example 3: Food test analysis (5 marks)
Question: A student tested three Caribbean foods (cassava, saltfish, coconut) for different nutrients. Results shown below:
| Food | Iodine test | Benedict's test | Biuret test |
|---|---|---|---|
| Cassava | Blue-black | Orange | No change |
| Saltfish | No change | No change | Purple |
| Coconut | No change | No change | No change |
(a) State which nutrient is present in cassava [1 mark] (b) Explain the result for saltfish with Biuret reagent [2 marks] (c) Suggest why coconut gave negative results for all three tests [2 marks]
Mark scheme answer:
(a) Starch [1 mark]
(b) Purple colour indicates presence of protein [1 mark]; saltfish is dried cod which contains high levels of protein [1 mark]
(c) Coconut contains mainly fat/lipids [1 mark] which are not detected by starch, sugar or protein tests [1 mark]
Common mistakes and how to avoid them
Confusing vitamins with their deficiency diseases — Learn the specific vitamin-deficiency link. Remember: vitamin C = scurvy, vitamin D + calcium = rickets. Use the mnemonic "C for Scurvy" (both have 'c' sound).
Stating that fibre is digested — Fibre (roughage) is NOT digested; it provides bulk to help food move through the intestines. It's the undigested portion that matters.
Claiming proteins are the main energy source — Carbohydrates are the primary energy source. Proteins are mainly for growth and repair; they're only used for energy when carbohydrates and fats are depleted.
Mixing up kwashiorkor and marasmus — Kwashiorkor = protein deficiency with swollen belly; Marasmus = protein AND energy deficiency with extreme wasting. The swollen belly is key to identifying kwashiorkor.
Writing vague answers about balanced diets — Always specify which nutrients and WHY for that particular person. Link age, activity, and gender to specific nutrient needs with clear reasoning.
Forgetting water as a nutrient — Many students list only five nutrient groups. Water is essential and counts as the sixth nutrient (some syllabi count fibre separately as the seventh).
Exam technique for Nutrition
Command words matter — "State" requires a simple fact (1 mark). "Explain" requires a reason/mechanism (usually 2 marks). "Describe" needs characteristics or changes observed. Always give reasons when asked to explain.
Use specific nutrient names — Write "vitamin C" or "ascorbic acid," not just "vitamins." Write "calcium" or "iron," not just "minerals." Specific names earn marks; general terms often don't.
Link structure to function — When discussing nutrients, connect the food source → nutrient → function → consequence of deficiency. This logical chain earns maximum marks in extended answers.
Food tests require precision — State the colour change (from → to) and whether heat is needed. "Positive result" without describing the colour change earns no marks. Remember initial colours: Benedict's is blue, iodine is brown.
Quick revision summary
Nutrition involves six nutrient groups: carbohydrates and fats for energy; proteins for growth and repair; vitamins and minerals for specific functions; water as solvent and transport; fibre for intestinal health. A balanced diet varies with age, activity, gender and climate. Malnutrition includes undernutrition (starvation, kwashiorkor, marasmus) and overnutrition (obesity). Deficiency diseases result from lacking specific nutrients: anaemia (iron), scurvy (vitamin C), rickets (calcium/vitamin D), goitre (iodine). Food tests use chemical reagents producing characteristic colour changes to identify nutrients.