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This lesson covers two closely linked minerals — calcium and phosphorus — as required by AQA GCSE Food Preparation and Nutrition (8585), specification section 3.2.2. Calcium is one of the most important minerals in the human body, and phosphorus works alongside it to build and maintain strong bones and teeth. Understanding their functions, sources, and deficiency effects is essential for the exam.
Minerals are inorganic nutrients required by the body in varying amounts. Unlike vitamins, minerals are chemical elements — they cannot be broken down or destroyed by heat, water, or air. However, like water-soluble vitamins, some minerals can dissolve in cooking water and be lost if the water is discarded.
Minerals are divided into two categories:
| Category | Description | Examples |
|---|---|---|
| Macro minerals | Needed in relatively large amounts (more than 100 mg/day) | Calcium, phosphorus, sodium, potassium, magnesium |
| Trace minerals (trace elements) | Needed in very small amounts (less than 100 mg/day) | Iron, fluoride, iodine, zinc, selenium |
graph TD
A["Minerals"] --> B["Macro Minerals"]
A --> C["Trace Minerals"]
B --> D["Calcium"]
B --> E["Phosphorus"]
B --> F["Sodium"]
C --> G["Iron"]
C --> H["Fluoride"]
C --> I["Iodine"]
style B fill:#e67e22,color:#fff
style C fill:#3498db,color:#fff
style D fill:#d35400,color:#fff
style E fill:#d35400,color:#fff
style F fill:#d35400,color:#fff
style G fill:#2980b9,color:#fff
style H fill:#2980b9,color:#fff
style I fill:#2980b9,color:#fff
Exam Tip: Unlike vitamins, minerals cannot be destroyed by cooking. However, they can dissolve in cooking water — so the same strategies for minimising water-soluble vitamin loss (using minimal water, steaming, using cooking water) also help retain minerals.
Calcium is the most abundant mineral in the human body. Approximately 99% of the body's calcium is found in bones and teeth, with the remaining 1% in blood and soft tissues.
| Function | Detail |
|---|---|
| Bones and teeth | Calcium is the primary mineral component of hydroxyapatite, the crystalline structure that gives bones and teeth their hardness and strength. Adequate calcium intake throughout life is essential for building and maintaining strong bones. |
| Blood clotting | Calcium is one of several factors required for the blood clotting cascade — the series of reactions that form a blood clot to stop bleeding. |
| Muscle contraction | Calcium ions trigger muscle fibres to contract. This includes skeletal muscles (movement), smooth muscles (digestion, blood vessel tone), and cardiac muscle (heartbeat). |
| Nerve function | Calcium is involved in transmitting nerve impulses between nerve cells. |
| Enzyme activation | Some enzymes require calcium as a cofactor to function properly. |
| Source Type | Examples |
|---|---|
| Dairy products | Milk, cheese (especially hard cheese like Cheddar), yoghurt — the richest and most easily absorbed sources in the UK diet |
| Green leafy vegetables | Broccoli, kale, spinach (though calcium from spinach is less well absorbed due to oxalic acid) |
| Fortified foods | White and brown flour in the UK is fortified with calcium by law; some plant milks, orange juice, and breakfast cereals are also fortified |
| Fish with edible bones | Sardines, pilchards, whitebait |
| Tofu | Calcium-set tofu is a good source |
| Nuts | Almonds, Brazil nuts |
| Hard water | In areas with hard water, tap water contributes to calcium intake |
Exam Tip: The fact that UK flour (except wholemeal) is fortified with calcium by law is a commonly tested point. This means bread and other flour-based products are significant calcium sources for many people.
This is a critical exam concept:
flowchart LR
A["Calcium in Food"] --> B["Small Intestine"]
C["Vitamin D"] -->|"enables<br/>absorption"| B
B --> D["Calcium absorbed<br/>into bloodstream"]
D --> E["Deposited in<br/>Bones & Teeth"]
style A fill:#e67e22,color:#fff
style C fill:#f1c40f,color:#000
style D fill:#27ae60,color:#fff
style E fill:#2ecc71,color:#fff
| Condition | Who It Affects | Description |
|---|---|---|
| Rickets | Children | Bones become soft and weak due to poor mineralisation. Symptoms include bowed legs, delayed growth, and skeletal deformities. (Note: rickets is caused by deficiency of calcium, Vitamin D, or both.) |
| Osteoporosis | Mainly older adults, especially post-menopausal women | Bones become brittle and porous due to loss of bone density over time. Bones break easily, particularly the hip, wrist, and spine. Osteoporosis develops silently over years. |
| Osteomalacia | Adults | Bones become soft and painful due to inadequate mineralisation (the adult equivalent of rickets). |
| Poor blood clotting | All ages | Reduced ability to form clots, leading to prolonged bleeding. |
| Muscle cramps | All ages | Inadequate calcium for muscle contraction can cause involuntary muscle spasms. |
| Group | Reason |
|---|---|
| Teenagers | Rapid bone growth increases calcium demand; many teenagers have low dairy intake. |
| Post-menopausal women | Declining oestrogen levels accelerate bone loss, increasing calcium requirements. |
| Vegans | No dairy products in the diet; must rely on fortified foods, green leafy vegetables, and calcium-set tofu. |
| People with lactose intolerance | Difficulty digesting dairy products may lead to reduced calcium intake. |
| Older adults | Reduced Vitamin D production, reduced absorption efficiency, and lower dietary intake. |
Exam Tip: Osteoporosis is a major public health concern. If asked about dietary advice for bone health, mention both calcium (dairy, fortified foods) and Vitamin D (sunlight, oily fish, supplements), regular weight-bearing exercise, and reducing risk factors (smoking, excess alcohol).
Phosphorus is the second most abundant mineral in the body. It works closely with calcium in forming bones and teeth.
| Function | Detail |
|---|---|
| Bones and teeth | Phosphorus combines with calcium to form calcium phosphate (hydroxyapatite), the mineral compound that gives bones and teeth their rigid structure. |
| Energy release | Phosphorus is a component of ATP (adenosine triphosphate), the molecule that stores and releases energy in cells. |
| Cell membranes | Phosphorus is part of phospholipids, which form the structure of every cell membrane in the body. |
| DNA and RNA | Phosphorus is a component of the nucleic acids (DNA and RNA) that carry genetic information. |
| pH regulation | Phosphorus-containing compounds help maintain the acid-base balance (pH) of body fluids. |
Phosphorus is found in a wide range of foods, so deficiency is rare:
| Source Type | Examples |
|---|---|
| Meat and poultry | Beef, chicken, pork, lamb |
| Fish | Salmon, tuna, cod, prawns |
| Dairy | Milk, cheese, yoghurt |
| Eggs | |
| Cereals and grains | Bread, rice, oats, breakfast cereals |
| Nuts and seeds | Sunflower seeds, pumpkin seeds, almonds |
| Pulses | Lentils, chickpeas, kidney beans |
Phosphorus deficiency is very rare in the UK and in most developed countries because phosphorus is present in such a wide range of foods. When it does occur (usually due to certain medical conditions or medications), symptoms include:
Excessive phosphorus intake (particularly from processed foods and fizzy drinks that contain phosphoric acid) may:
| Feature | Calcium | Phosphorus |
|---|---|---|
| Type | Macro mineral | Macro mineral |
| Key function | Bones, teeth, blood clotting, muscle contraction | Bones, teeth, energy (ATP), cell membranes |
| Best sources | Dairy, fortified flour, green leafy veg | Meat, fish, dairy, eggs, cereals |
| Deficiency | Rickets, osteoporosis, osteomalacia | Very rare |
| Works with | Vitamin D (for absorption) | Calcium (in bone formation) |
| UK fortification | Added to white/brown flour | Not typically fortified (widespread in diet) |
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