Chapter: Nutrients in Food

Welcome to your study notes for Nutrients in Food, part of Unit A2 7: Human Nutrition and Health in CCEA GCE Health and Social Care. Understanding nutrients isn't just about passing your exam—it helps us understand how the human body grows, repairs itself, stays healthy, and fights illness. In health and social care settings, knowing what people eat and why they need specific nutrients is essential for caring for vulnerable service users such as infants, pregnant women, and older adults in residential care.

Don't worry if nutrition feels like a lot of science at first! We will break everything down into manageable sections, covering macronutrients, micronutrients, water, and their real-world applications in health and care settings.

1. Understanding Nutrients: The Big Picture

Nutrients are chemical substances found in food that the body requires to live, grow, and maintain health. We classify them into two main categories:

  • Macronutrients: Nutrients that our bodies need in large quantities each day. These are Proteins, Carbohydrates, and Lipids (Fats and Oils). They provide energy and structural materials for the body.
  • Micronutrients: Nutrients that our bodies need in tiny amounts (milligrams or micrograms), but are still vital for survival. These include Vitamins and Minerals.
  • Water: An essential nutrient required in large quantities for almost every bodily process.

2. Macronutrient 1: Proteins

Functions of Protein in the Body

Think of protein as the building blocks of the body. Its main roles are:

  • Growth, repair, and maintenance: Building new cells (essential for growing children and healing wounds) and repairing damaged body tissues.
  • Production of vital substances: Synthesising enzymes (to digest food and drive chemical reactions), antibodies (to defend against infection), hormones, and transport proteins such as haemoglobin (which carries oxygen in red blood cells).
  • Secondary energy source: The body prefers to use carbohydrates and fats for energy, but if these are depleted, protein can be broken down to supply energy.

Structure and Classification of Proteins

Proteins are made up of smaller sub-units called amino acids. There are two main types of amino acids:

  • Essential Amino Acids: Cannot be made by the body and must be obtained directly from the diet.
  • Non-essential Amino Acids: Can be synthesised (made) by the human body from other compounds.

Based on their amino acid profile, dietary proteins are divided into two categories:

  • High Biological Value (HBV) Proteins: Contain all the essential amino acids that our bodies cannot make.
    Dietary sources: Meat, poultry, fish, eggs, dairy products (milk, cheese, yoghurt), and soya.
  • Low Biological Value (LBV) Proteins: Lack one or more of the essential amino acids.
    Dietary sources: Pulses (lentils, beans, chickpeas), nuts, seeds, and cereals (wheat, oats, rice).

Health Implications: Deficiency and Excess

  • Protein Deficiency: Leads to Protein-Energy Malnutrition (PEM), including conditions such as Kwashiorkor. Symptoms include muscle wasting, delayed wound healing, and impaired immune function (making service users more vulnerable to infections).
  • Protein Excess: Consuming far more protein than the body needs can put extra strain on renal function (the kidneys), which have to filter out the nitrogen-containing waste products of protein breakdown.

Key Takeaway: HBV proteins provide all essential amino acids (mostly animal sources and soya), while LBV proteins are missing some (plant sources). Protein is vital for growth, tissue repair, enzyme and antibody production.

3. Macronutrient 2: Carbohydrates

Functions of Carbohydrates

  • Primary source of energy: Carbohydrates provide \(17\text{ kJ}\) (\(4\text{ kcal}\)) per gram. They are broken down into glucose, which fuels cellular respiration and powers the central nervous system (the brain relies almost entirely on glucose).

Classification of Carbohydrates

Carbohydrates are classified based on the complexity of their molecular structures:

A. Monosaccharides (Single Sugar Units)
  • Glucose: Found in ripe fruits, vegetables, and honey; the main sugar circulating in blood.
  • Fructose: Fruit sugar found in fruits, berries, and honey.
  • Galactose: Found in milk (as part of lactose).
B. Disaccharides (Double Sugar Units - two monosaccharides joined together)
  • Sucrose: Table sugar (glucose + fructose), extracted from sugar beet and sugar cane.
  • Lactose: Milk sugar (glucose + galactose), found in dairy foods.
  • Maltose: Malt sugar (glucose + glucose), formed during the breakdown of starch (e.g., in germinating grains).
C. Polysaccharides (Complex Carbohydrates / Long Chains)
  • Starch: The main energy storage carbohydrate in plants. Found in potatoes, bread, rice, pasta, and cereals. Broken down slowly, providing sustained energy.
  • Glycogen: The storage form of carbohydrate in human liver and muscle cells.
  • Non-Starch Polysaccharide (NSP / Dietary Fibre): Structural carbohydrate from plant cell walls that cannot be digested by human digestive enzymes.
Free/Added Sugars vs. Intrinsic Sugars
  • Free/Added Sugars: Sugars added to foods by manufacturers, cooks, or consumers, plus sugars naturally present in honey, syrups, and unsweetened fruit juices. High intakes contribute to dental caries and energy imbalance.
  • Intrinsic Sugars: Sugars naturally integrated into the cellular structure of whole, unprocessed fruits and vegetables.

Dietary Fibre (Non-Starch Polysaccharides - NSP)

Although our bodies cannot digest fibre to obtain energy, it is critical for bowel health. There are two main forms:

  • Insoluble Fibre: Adds bulk to stools, stimulates peristalsis (the wave-like muscle contractions of the gut), reduces transit time, and prevents constipation and diverticular disease. Sources: Wholemeal flour, bran, nuts, whole grains.
  • Soluble Fibre: Dissolves in water to form a gel-like substance in the gut. Helps to lower blood cholesterol levels and regulate blood glucose. Sources: Oats, pulses (beans, lentils), apples, citrus fruits.
  • A diet rich in total NSP is strongly associated with a reduced risk of bowel cancer.

Key Takeaway: Carbohydrates provide our primary energy (\(17\text{ kJ/g}\)). Complex starches provide sustained energy, while dietary fibre (NSP) is vital for digestive health and preventing constipation, diverticular disease, and bowel cancers.

4. Macronutrient 3: Lipids (Fats & Oils)

Functions of Lipids

  • Concentrated energy store: Provides \(37\text{ kJ}\) (\(9\text{ kcal}\)) per gram—more than double that of protein or carbohydrates!
  • Subcutaneous insulation: A layer of fat under the skin helps maintain core body temperature.
  • Protection of vital organs: Cushions organs such as the kidneys and heart against physical trauma.
  • Transport and absorption of fat-soluble vitamins: Required to absorb and carry Vitamins A, D, E, and K through the bloodstream.
  • Cell membrane structure: Essential constituent of every cell membrane in the body.

Classification of Fatty Acids

Lipids are formed from glycerol and fatty acids. They are classified into different groups:

  • Saturated Fatty Acids:
    Sources: Mostly animal sources (butter, lard, fatty cuts of meat, full-fat dairy) and tropical oils (palm oil, coconut oil).
    Health impact: High intakes are associated with elevated LDL (Low-Density Lipoprotein) cholesterol, increasing the risk of cardiovascular disease.
  • Monounsaturated Fatty Acids (MUFAs):
    Sources: Olive oil, rapeseed oil, avocados, almonds.
    Health impact: Help protect the heart by maintaining healthy cholesterol levels.
  • Polyunsaturated Fatty Acids (PUFAs):
    Sources: Split into two essential groups:
    • Omega-3 fatty acids (alpha-linolenic acid): Found in oily fish (salmon, mackerel, sardines), flaxseeds, and walnuts.
    • Omega-6 fatty acids (linoleic acid): Found in vegetable oils (sunflower, corn oil) and seeds.
  • Trans Fatty Acids: Formed industrially during the hydrogenation of liquid vegetable oils to create solid fats (e.g., in some commercial baked goods and margarines). Harmful to cardiovascular health.

Key Takeaway: Lipids give us concentrated energy (\(37\text{ kJ/g}\)), insulate our bodies, protect organs, and allow absorption of fat-soluble vitamins (A, D, E, K). Replacing saturated fats with unsaturated fats (MUFAs and PUFAs) supports cardiovascular health.

5. Micronutrients: Fat-Soluble Vitamins

Fat-soluble vitamins (A, D, E, K) dissolve in fat and can be stored in the liver and adipose tissue for future use. This means we do not necessarily need them every single day, but excess consumption can build up to toxic levels over time.

Memory Trick: Remember "ADEK"—the four fat-soluble vitamins!

Vitamin A (Retinol & Beta-Carotene)

  • Functions: Essential for normal vision (forming rhodopsin, a visual pigment needed for vision in dim light); maintains healthy skin and mucous membranes; supports immune function.
  • Sources:
    • Retinol (pre-formed Vitamin A): Liver, whole milk, butter, cheese, oily fish.
    • Beta-carotene (provitamin A, converted to Vitamin A in the gut): Orange and green leafy vegetables such as carrots, sweet potatoes, spinach, and peppers.
  • Deficiency: Night blindness (difficulty seeing in dim light) and, in severe cases, xerophthalmia (dryness and corneal damage that can cause permanent blindness).

Vitamin D (Cholecalciferol)

  • Functions: Facilitates the absorption and mineralisation of calcium and phosphorus from the gut into bones and teeth.
  • Sources: Action of sunlight (UVB rays) on the skin; oily fish (salmon, sardines), egg yolks, fortified breakfast cereals, and fortified spreads.
  • Deficiency:
    • In children: Rickets (soft, weak bones causing skeletal deformities such as bow legs).
    • In adults: Osteomalacia (softening of bones, causing bone pain and weakness) and contributes to osteoporosis (reduced bone density, increasing fracture risk).

Vitamin E (Tocopherols)

  • Functions: Acts as a powerful antioxidant, protecting cell membranes from oxidative damage caused by free radicals.
  • Sources: Vegetable oils, nuts, seeds, wheatgerm, leafy green vegetables.

Vitamin K (Phylloquinone & Menaquinone)

  • Functions: Essential for normal blood clotting (specifically required for the liver to synthesise prothrombin) and supports bone metabolism.
  • Sources: Dark green leafy vegetables (spinach, kale, broccoli) and synthesis by normal intestinal bacteria in the gut.

6. Micronutrients: Water-Soluble Vitamins

Water-soluble vitamins (B-Complex and Vitamin C) dissolve in water. They are not stored in significant quantities in the body; any excess is excreted in urine. Therefore, they must be supplied regularly through our daily diet.

B-Complex Vitamins

Thiamin (\(B_1\)), Riboflavin (\(B_2\)), and Niacin (\(B_3\))
  • Functions: Act as essential co-enzymes involved in cellular respiration, facilitating the release of energy from carbohydrates, fats, and proteins.
  • Sources: Fortified breakfast cereals, whole grains, yeast extracts, lean meat, eggs, dairy.
  • Deficiency:
    • Thiamin (\(B_1\)) deficiency causes Beriberi (characterised by nerve damage, muscle weakness, and heart problems).
    • Niacin (\(B_3\)) deficiency causes Pellagra (characterised by the classic symptoms: dermatitis, diarrhoea, and dementia).
Folate / Folic Acid (\(B_9\))
  • Functions: Essential for DNA synthesis, healthy cell division, and the formation of healthy red blood cells alongside Vitamin \(B_{12}\). Critical during early pregnancy for the development of the fetal neural tube.
  • Sources: Green leafy vegetables (spinach, broccoli), fortified breakfast cereals, pulses (lentils, chickpeas), and citrus fruits.
  • Deficiency: Megaloblastic anaemia (large, immature red blood cells). In early pregnancy, deficiency causes Neural Tube Defects (NTDs) such as spina bifida in the developing baby.
Vitamin \(B_{12}\) (Cobalamin)
  • Functions: Maintains healthy nerve cells and the myelin sheath (the protective insulation around nerves); works with folate to produce red blood cells.
  • Sources: Exclusively found in animal-derived foods (meat, fish, eggs, dairy) and fortified products (fortified yeast extracts, fortified breakfast cereals, fortified plant milks).
  • Deficiency: Pernicious anaemia (large red blood cells, severe fatigue) and irreversible neurological damage (tingling, numbness, memory impairment). Vegans are at high risk if they do not consume fortified foods or supplements.

Vitamin C (Ascorbic Acid)

  • Functions:
    • Required for collagen synthesis (a structural protein that holds skin, blood vessels, cartilage, and bone together; vital for wound healing).
    • Acts as an antioxidant.
    • Greatly enhances the absorption of non-haem iron (plant-based iron) in the digestive tract when eaten at the same meal.
  • Sources: Citrus fruits (oranges, lemons, grapefruits), kiwis, strawberries, bell peppers, tomatoes, and green vegetables (broccoli, Brussels sprouts).
  • Deficiency: Scurvy (symptoms include bleeding gums, loose teeth, pinpoint skin haemorrhages / petechiae, slow wound healing, and joint pain).

Key Takeaway: Water-soluble vitamins cannot be stored in large amounts. B vitamins are co-enzymes for energy release; Folate prevents spina bifida; \(B_{12}\) protects nerves and makes red blood cells; Vitamin C makes collagen, heals wounds, and helps absorb non-haem iron.

7. Micronutrients: Key Minerals and Trace Elements

Calcium

  • Functions:
    • Mineralisation of bones and teeth, providing hardness and strength.
    • Essential for blood clotting.
    • Enables normal muscle contraction (including cardiac muscle).
    • Facilitates nerve impulse transmission.
  • Sources: Milk, cheese, yoghurt, calcium-fortified plant milks, tofu, canned bony fish (e.g., canned sardines and salmon where bones are eaten), and green leafy vegetables.
  • Health Implications: Inadequate calcium intake leads to low peak bone mass and increases the risk of osteoporosis in later life.

Iron

  • Functions: Essential for the synthesis of haemoglobin in red blood cells (which transports oxygen around the body) and myoglobin (which stores oxygen in muscle tissue); part of cellular enzyme systems.
  • Types of Dietary Iron:
    • Haem Iron: Found in animal tissue (red meat, offal such as liver, poultry, fish). Has a high bioavailability (readily absorbed by the human gut).
    • Non-Haem Iron: Found in plant foods (pulses, beans, lentils, dried fruits, fortified cereals, dark green leafy vegetables). Has lower bioavailability (absorbed less efficiently).
  • Bioavailability Tip: Consuming Vitamin C alongside non-haem iron converts it into a more soluble form, greatly boosting its absorption!
  • Deficiency: Iron Deficiency Anaemia. Symptoms include extreme fatigue, lethargy, breathlessness, pale skin, and dizziness due to reduced oxygen delivery to tissues.

Sodium and Potassium: The Electrolyte Balance

  • Sodium:
    Functions: Regulates extracellular fluid and electrolyte balance, maintains normal blood volume and blood pressure, and supports nerve transmission.
    Excess Intake: Strongly linked directly to hypertension (high blood pressure), which is a major risk factor for stroke and coronary heart disease.
  • Potassium:
    Functions: Regulates intracellular fluid balance, supports normal muscle and nerve function, and counteracts the blood-pressure-raising effects of sodium.
    Sources: Bananas, potatoes, tomatoes, pulses, and leafy green vegetables.

8. Water and Hydration

Water is an essential nutrient that makes up approximately \(60\%\) of adult body weight. Without adequate water, the human body cannot survive more than a few days.

Key Functions of Water

  • Metabolic solvent: Provides the aqueous medium in which chemical and metabolic reactions occur within cells.
  • Temperature regulation: Regulates core body temperature through the evaporation of sweat (perspiration) from the skin surface.
  • Excretion of waste: Allows the kidneys to filter waste products from the blood and excrete them in urine; also softens stools to prevent constipation.
  • Lubrication and protection: Forms synovial fluid to lubricate joints and acts as a cushion for delicate tissues like the brain and eyes.
  • Transport medium: Forms the liquid basis of blood plasma, enabling the transport of nutrients, hormones, oxygen, and waste products throughout the body.

9. Applied Nutrition in Health and Social Care Contexts

In CCEA A2 7 exams, you will be asked to apply your nutritional knowledge to specific service users. Here is how nutrient requirements apply across different life stages and care settings:

A. Pregnant Women

  • Folate / Folic Acid: Crucial before conception and during the first 12 weeks of pregnancy to prevent neural tube defects such as spina bifida.
  • Iron & Vitamin C: Extra iron is needed to produce maternal red blood cells and supply the growing placenta and fetus; Vitamin C should be consumed simultaneously to maximise non-haem iron absorption.
  • Calcium & Vitamin D: Needed for mineralisation of the developing fetal skeleton without depleting maternal bone stores.

B. Older Adults in Residential Care

  • Hydration / Water: Older adults frequently have a reduced thirst mechanism and may restrict fluid intake due to mobility issues or fear of incontinence. Staff must encourage regular fluids to prevent dehydration, confusion, urinary tract infections, and constipation.
  • Dietary Fibre (NSP): Slower gut motility makes older adults prone to constipation; adequate insoluble fibre and fluids are vital.
  • Protein: Needed to maintain muscle mass (counteracting sarcopenia) and promote wound healing (e.g., pressure sores).
  • Vitamin D & Calcium: Older adults may have limited sun exposure; adequate vitamin D and calcium protect against osteomalacia, osteoporosis, and fall-related fractures.

C. Infants and Young Children

  • High Energy and Protein: Rapid growth demands nutrient-dense meals with adequate HBV protein and energy.
  • Iron: Weaning diets must introduce iron-rich foods (e.g., puréed meat, fortified baby cereals, pulses) because natural infant iron stores deplete around 6 months of age.
  • Vitamin D: Crucial during bone growth to prevent childhood rickets.

10. Common Exam Pitfalls & Examiner Advice

  • Don't just name food sources when asked for nutrient functions: Stating that "fruit gives you energy" will not earn full marks. Instead, write: "Fruit contains monosaccharides (fructose and glucose) which are broken down during respiration to release cellular energy."
  • Distinguish Haem from Non-Haem Iron: Always mention that haem iron (meat) is more bioavailable (easily absorbed) than non-haem iron (plants), and explain that Vitamin C aids the absorption of non-haem iron.
  • Be precise with deficiency names: Avoid vague phrases like "poor bones". Use precise medical terminology: Rickets in children, Osteomalacia or Osteoporosis in adults, Scurvy for Vitamin C, Pernicious Anaemia for \(B_{12}\), and Neural Tube Defects / Spina Bifida for folate.
  • Link directly to the care scenario: Always refer to the specific service user named in the exam stem (e.g., explaining why an elderly resident in a nursing home needs extra fluids or why a pregnant service user needs folic acid).

Quick Review: Summary of Nutrients

  • Protein: Growth, repair, enzymes, antibodies. HBV (meat/dairy/soya) vs. LBV (pulses/grains). Deficiency = PEM / Kwashiorkor.
  • Carbohydrates: Primary energy (\(17\text{ kJ/g}\)). Includes sugars, starches, and NSP (fibre) for bowel health and preventing constipation.
  • Lipids: Concentrated energy store (\(37\text{ kJ/g}\)), insulation, organ protection, carries vitamins A, D, E, K. Saturated fats raise LDL cholesterol; unsaturated fats are protective.
  • Fat-Soluble Vitamins: A (vision/skin), D (calcium absorption/bones), E (antioxidant), K (blood clotting).
  • Water-Soluble Vitamins: B-group (energy release), Folate (prevents spina bifida), \(B_{12}\) (nerves/red blood cells), C (collagen/wound healing/iron absorption).
  • Minerals: Calcium (bones/teeth/clotting), Iron (haemoglobin/oxygen transport), Sodium & Potassium (fluid balance/blood pressure).
  • Water: Solvent, temperature control, waste excretion, joint lubrication, plasma transport.