Fat-Soluble Vitamins E and K

This lesson covers Vitamin E and Vitamin K, completing the four fat-soluble vitamins you need to know for AQA GCSE Food Preparation and Nutrition (8585), specification section 3.2.2. While Vitamins A and D tend to receive more exam attention, Vitamins E and K are still examinable and regularly appear in shorter-answer questions.

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Vitamin E (Tocopherol)

Vitamin E is a powerful antioxidant vitamin. Its primary role in the body is to protect cells from damage caused by free radicals — unstable molecules produced during normal metabolism and by environmental factors such as pollution, cigarette smoke, and UV radiation.

Functions of Vitamin E

Function	Detail
Antioxidant protection	Vitamin E protects cell membranes from oxidative damage by neutralising free radicals. Cell membranes are made largely of unsaturated fatty acids, which are vulnerable to attack.
Immune support	By protecting immune cells from oxidative stress, Vitamin E helps maintain a healthy immune system.
Skin health	Vitamin E contributes to maintaining healthy skin and may help protect against UV damage.
Heart health	Antioxidant activity may help protect against cardiovascular disease by preventing the oxidation of LDL cholesterol (though this is more relevant at A-Level).

What Are Free Radicals?

Free radicals are highly reactive molecules that have an unpaired electron. They can damage cells by attacking cell membranes, proteins, and DNA. This damage is known as oxidative stress and is linked to ageing, cancer, and heart disease. Antioxidants like Vitamin E donate an electron to free radicals, neutralising them and preventing further damage.

flowchart LR
    A["Free Radical<br/>(unstable)"] -->|"attacks"| B["Cell Membrane"]
    C["Vitamin E<br/>(antioxidant)"] -->|"donates electron"| A
    C -->|"neutralises"| D["Stable Molecule<br/>(harmless)"]
    B -->|"damage prevented"| E["Healthy Cell"]

    style A fill:#c0392b,color:#fff
    style C fill:#27ae60,color:#fff
    style D fill:#2ecc71,color:#fff
    style E fill:#3498db,color:#fff

Sources of Vitamin E

Source Type	Examples
Plant oils	Sunflower oil, olive oil, rapeseed oil, soya oil
Nuts and seeds	Almonds, hazelnuts, sunflower seeds, peanuts
Cereals and grains	Wheatgerm, wholegrain cereals
Green vegetables	Spinach, broccoli
Other	Avocado, sweet potato

Exam Tip: If asked to name a good source of Vitamin E, plant oils and nuts are the strongest answers. These are the richest dietary sources.

Deficiency of Vitamin E

Vitamin E deficiency is rare in the UK because the vitamin is widely available in the diet. However, when it does occur:

• Weakness and fatigue — due to damage to muscle cells.
• Impaired immune function — increased susceptibility to infection.
• Nerve damage — in severe, prolonged deficiency.
• Premature ageing of cells — due to uncontrolled oxidative damage.

Deficiency is most likely in individuals with conditions that impair fat absorption (such as cystic fibrosis, coeliac disease, or Crohn's disease), since Vitamin E requires fat for absorption.

Excess of Vitamin E

Vitamin E excess from food alone is extremely unlikely. However, high-dose supplements may cause:

• Nausea and digestive discomfort.
• In very high doses, an increased risk of bleeding because Vitamin E can act as a blood thinner (anticoagulant).

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Vitamin K (Phylloquinone / Menaquinone)

Vitamin K is essential for blood clotting and bone health. It exists in two main forms:

1. Phylloquinone (K1) — found in plant foods, especially green leafy vegetables.
2. Menaquinone (K2) — produced by bacteria in the gut and also found in some fermented foods and animal products.

Functions of Vitamin K

Function	Detail
Blood clotting	Vitamin K is required for the synthesis of several clotting factors (proteins) in the liver. Without Vitamin K, blood cannot clot properly, leading to prolonged bleeding even from minor wounds.
Bone metabolism	Vitamin K helps activate osteocalcin, a protein involved in binding calcium to bone tissue, supporting bone mineralisation.
Wound healing	Closely linked to blood clotting — Vitamin K enables the body to form clots that stop bleeding, which is the first step in wound healing.

How Blood Clotting Works (Simplified)

flowchart LR
    A["Injury occurs"] --> B["Platelets gather<br/>at wound site"]
    B --> C["Clotting factors<br/>activated"]
    C -->|"Vitamin K<br/>required"| D["Fibrin threads<br/>form a mesh"]
    D --> E["Blood clot seals<br/>the wound"]

    style C fill:#8e44ad,color:#fff
    style D fill:#e74c3c,color:#fff
    style E fill:#27ae60,color:#fff

Sources of Vitamin K