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. AQA examiners have noted this in mark schemes.

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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: