Water-Soluble Vitamin C

This lesson covers Vitamin C (ascorbic acid), the final water-soluble vitamin you need to know for AQA GCSE Food Preparation and Nutrition (8585), specification section 3.2.2. Vitamin C is one of the most commonly examined vitamins because of its wide range of functions, its vulnerability to destruction during cooking, and its famous deficiency disease — scurvy.

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Functions of Vitamin C

Vitamin C has many important functions in the body:

Function	Detail
Collagen formation	Vitamin C is essential for the synthesis of collagen, a structural protein found in skin, blood vessels, tendons, ligaments, cartilage, bones, and gums. Without adequate Vitamin C, collagen cannot form properly, leading to weakened connective tissue.
Wound healing	Because collagen is essential for tissue repair, Vitamin C is crucial for healing wounds, cuts, and burns. It also helps maintain the integrity of blood vessel walls.
Iron absorption	Vitamin C significantly enhances the absorption of non-haem iron (the type of iron found in plant foods) from the small intestine. Consuming Vitamin C alongside iron-rich foods can dramatically improve iron uptake.
Antioxidant	Vitamin C is a powerful antioxidant that protects cells from damage by free radicals. It works in the watery parts of cells (complementing Vitamin E, which works in the fatty parts).
Immune function	Vitamin C supports the immune system by stimulating the production and activity of white blood cells and acting as a barrier-defence antioxidant.
Healthy skin	Through its role in collagen production, Vitamin C helps maintain healthy, firm skin.

The Iron Absorption Link

This is a particularly important and frequently examined point. Iron from plant sources (non-haem iron) is less easily absorbed than iron from animal sources (haem iron). Vitamin C converts non-haem iron into a form that the body can absorb more readily.

Practical example: Drinking a glass of orange juice with a meal containing beans or lentils will significantly increase the amount of iron absorbed from those foods.

flowchart LR
    A["Non-Haem Iron<br/>(plant sources)"] -->|"poorly absorbed<br/>on its own"| B["Small Intestine"]
    C["Vitamin C"] -->|"enhances<br/>absorption"| B
    B --> D["Iron absorbed<br/>into bloodstream"]

    style A fill:#e67e22,color:#fff
    style C fill:#f1c40f,color:#000
    style D fill:#27ae60,color:#fff

Exam Tip: The Vitamin C and iron absorption link is tested regularly. If a question asks how a vegetarian or vegan can improve their iron intake, one of the best answers is to eat Vitamin C-rich foods alongside iron-rich plant foods.

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Sources of Vitamin C

Vitamin C is found almost exclusively in fruits and vegetables. It is not present in significant amounts in animal products (with the exception of liver in small quantities).

Source Type	Examples
Citrus fruits	Oranges, lemons, limes, grapefruit, tangerines
Berries	Strawberries, blackcurrants, raspberries, blueberries
Vegetables	Red and green peppers (one of the richest sources), broccoli, Brussels sprouts, potatoes (due to the large quantities consumed in the UK diet)
Tropical fruits	Kiwi fruit, mangoes, pineapple, guava
Other	Tomatoes, cabbage, spinach, cauliflower
Fortified foods	Some fruit juices and drinks

Exam Tip: Potatoes are worth mentioning as a Vitamin C source — not because they are particularly rich, but because they are eaten in such large quantities in the UK that they contribute significantly to overall intake. This "low concentration but high consumption" point is often what distinguishes top-band answers on Vitamin C source questions.

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Deficiency of Vitamin C

Scurvy

Scurvy is the classic Vitamin C deficiency disease. It was historically common among sailors on long voyages who had no access to fresh fruit and vegetables for months.

Symptoms of scurvy include:

Symptom	Explanation
Bleeding, swollen gums	Weakened collagen in gum tissue causes gums to bleed easily and become inflamed. Teeth may loosen and fall out.
Slow wound healing	Without adequate collagen production, wounds heal very slowly or not at all.
Easy bruising	Weakened blood vessel walls break easily, causing bruises to appear with minimal impact.
Joint and muscle pain	Collagen is needed in connective tissue around joints; deficiency causes pain and swelling.
Tiredness and weakness	General fatigue and lethargy.
Dry, rough skin	Poor collagen formation affects skin texture.
Anaemia	Reduced iron absorption (due to lack of Vitamin C) can contribute to iron-deficiency anaemia.

Scurvy is now rare in the UK but can still occur in people with very restricted diets, particularly older adults, those with alcohol dependency, or individuals who eat virtually no fruit or vegetables.

Exam Tip: When writing about scurvy, always link the symptoms to the function of Vitamin C. For example: "Gums bleed because Vitamin C is needed to make collagen, which strengthens gum tissue. Without Vitamin C, collagen cannot be formed properly, so the gums become weak and bleed easily." This type of explanation shows understanding and earns higher marks.

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Vitamin C Loss During Cooking and Preparation

Vitamin C is the most easily destroyed vitamin. It is vulnerable to three main factors:

Factor	How It Causes Loss
Heat	Vitamin C is destroyed by high temperatures. Prolonged cooking at high heat causes significant losses.
Water	Being water-soluble, Vitamin C leaches into cooking water. If the cooking water is discarded, the vitamin is lost.
Air (oxidation)	Vitamin C is destroyed by exposure to oxygen in the air. Cut surfaces of fruit and vegetables lose Vitamin C on contact with air.
Alkali	Adding bicarbonate of soda to cooking water (sometimes done to preserve green colour) destroys Vitamin C.
Light	Prolonged exposure to light can degrade Vitamin C in some foods.
Time	The longer food is stored or left after preparation, the more Vitamin C is lost.

Strategies to Minimise Vitamin C Loss

These practical strategies are frequently tested in AQA exams:

Strategy	Explanation
Steam rather than boil	Steaming keeps food above the water, so Vitamin C cannot leach into it.
Use only a small amount of water	If boiling, use the minimum amount of water to reduce leaching.
Use the cooking water	Use the water from boiled vegetables in soups, gravies, or sauces to recover the dissolved vitamins.
Cook for the shortest time possible	Reduce exposure to heat by cooking vegetables until just tender.
Prepare just before cooking	Do not prepare vegetables hours in advance — cut surfaces lose Vitamin C to air.
Use a sharp knife	A sharp knife causes less cell damage than a blunt one, reducing the surface area exposed to air.
Do not soak vegetables	Soaking vegetables in water before cooking causes Vitamin C to dissolve into the soaking water.
Serve immediately	Do not keep cooked vegetables warm for long periods, as Vitamin C continues to be destroyed by heat.
Eat some raw fruit and vegetables	Raw foods retain all their Vitamin C, as no cooking losses occur.
Do not add bicarbonate of soda	Alkaline conditions destroy Vitamin C.
Cover pans	Using a lid reduces the amount of air in contact with the food, limiting oxidation.

Exam Tip: Questions about minimising vitamin loss during cooking are extremely common on AQA papers. Learn at least five strategies and be able to explain why each one works (e.g., "steaming avoids contact with water, so the water-soluble Vitamin C cannot dissolve into cooking water").

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Vitamin C as an Antioxidant

Vitamin C is one of three antioxidant vitamins (A, C, and E — the ACE vitamins). As an antioxidant, Vitamin C:

• Neutralises free radicals — donating electrons to stabilise these reactive molecules.
• Protects cells — particularly in the watery (aqueous) parts of the body, such as blood plasma and the interior of cells.
• Regenerates Vitamin E — Vitamin C can restore Vitamin E to its active antioxidant form after it has neutralised a free radical, meaning the two vitamins work together.

flowchart TD
    A["Free Radicals"] -->|"damage"| B["Cells / DNA / Proteins"]
    C["Antioxidant Vitamins"] -->|"neutralise"| A
    C --> D["Vitamin A<br/>(beta-carotene)"]
    C --> E["Vitamin C<br/>(water-soluble)"]
    C --> F["Vitamin E<br/>(fat-soluble)"]
    E -->|"regenerates"| F

    style A fill:#c0392b,color:#fff
    style C fill:#27ae60,color:#fff
    style D fill:#e67e22,color:#fff
    style E fill:#3498db,color:#fff
    style F fill:#f39c12,color:#fff

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Common Exam Mistakes