Minerals: Calcium and Phosphorus

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.

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What Are Minerals?

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.

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Calcium

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.

Functions of Calcium

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.

Sources of Calcium

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.

The Relationship Between Calcium and Vitamin D

This is a critical exam concept:

• Vitamin D is essential for the absorption of calcium from food in the small intestine.
• Without adequate Vitamin D, the body cannot absorb enough calcium, regardless of how much calcium is consumed.
• This means that calcium deficiency can occur even with adequate calcium intake if Vitamin D status is poor.
• For optimal bone health, both calcium and Vitamin D must be adequate.

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

Deficiency of Calcium