What are the fat-soluble and water-soluble vitamins, what do they do, and what happens if we get too little or too much?
Vitamins as micronutrients: the fat-soluble vitamins A, D, E and K and the water-soluble vitamins B group and C, their functions and food sources, the effects of deficiency and excess, and how vitamins can be lost or destroyed during food preparation and cooking.
A CCEA A-Level Nutrition and Food Science answer on vitamins: the fat-soluble vitamins A, D, E and K and the water-soluble B group and C, their functions and sources, the effects of deficiency and excess, and the loss of vitamins during food preparation and cooking.
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What this dot point is asking
CCEA wants you to classify vitamins as fat-soluble (A, D, E, K) or water-soluble (the B group and C), describe their functions and food sources, explain the effects of deficiency and excess, and explain how vitamins are lost or destroyed during food preparation, storage and cooking.
Fat-soluble and water-soluble vitamins
The fat-soluble vitamins: vitamin A (retinol and beta-carotene) is needed for vision in dim light, healthy skin and immunity (deficiency causes night blindness); vitamin D is needed for calcium and phosphorus absorption and strong bones (deficiency causes rickets and osteomalacia); vitamin E is an antioxidant protecting cell membranes; vitamin K is needed for normal blood clotting.
Loss in cooking, deficiency and excess
Because water-soluble vitamins dissolve and many vitamins are destroyed by heat, oxygen and light, food preparation matters. Vitamin C in particular is lost by leaching into cooking water, by prolonged heating, by cutting and exposing cells to air, and by adding bicarbonate of soda. Losses are reduced by preparing just before cooking, using minimal water (or steaming, microwaving, stir-frying), cooking quickly and serving promptly.
Examples in context
Example 1. Vitamin C and iron in a vegetarian meal. A vegetarian eating a lentil curry adds a squeeze of lemon and a side of peppers. The vitamin C converts the iron in the lentils to a form that is far more easily absorbed, so the meal delivers more usable iron than the lentils alone. This shows how vitamins interact with minerals, a favourite CCEA application.
Example 2. Fortification and supplements. Because vitamin D is hard to obtain from food and depends on limited UK sunlight, margarine and many breakfast cereals are fortified with it, and a 10 microgram daily supplement is advised in autumn and winter. This public-health approach links the nutrient to dietary guidelines and to the bone-health content of the course.
Try this
Q1. State one function and one good food source of vitamin A. [2 marks]
- Cue. Function: vision in dim light, healthy skin or immunity. Source: liver, oily fish, dairy or orange/green vegetables.
Q2. Explain why folate (folic acid) is recommended before and during early pregnancy. [2 marks]
- Cue. It reduces the risk of neural tube defects such as spina bifida in the developing baby.
Q3. Name the deficiency disease caused by a lack of vitamin C. [1 mark]
- Cue. Scurvy.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA AS 20196 marksExplain the importance of vitamin D in the diet and discuss why deficiency has become a concern in the United Kingdom.Show worked answer →
A 6-mark answer needs the functions of vitamin D, the consequences of deficiency, and the reasons deficiency is common.
Vitamin D is needed for the absorption of calcium and phosphorus from the gut, so it is essential for the formation and maintenance of strong bones and teeth. It works closely with calcium: without enough vitamin D, calcium cannot be absorbed efficiently however much is eaten.
A deficiency in children causes rickets, in which the bones soften and the legs bow under the body's weight; in adults it causes osteomalacia, with soft, painful bones, and it contributes to osteoporosis in later life.
Vitamin D is unusual because most is made in the skin by the action of sunlight, with only small amounts in food (oily fish, eggs, fortified spreads and cereals). Deficiency has become a concern because many people get little sun exposure, cover their skin, use sun cream, or have darker skin or housebound lifestyles, and the UK has limited winter sunlight. For these reasons a daily supplement of 10 micrograms is now advised, especially in autumn and winter.
Markers reward the calcium-absorption function, rickets and osteomalacia as deficiency diseases, the skin-synthesis point, the named food sources, and the lifestyle reasons for widespread deficiency.
CCEA AS 20214 marksDescribe how vitamin C can be lost during the preparation and cooking of vegetables, and suggest ways to reduce these losses.Show worked answer →
A 4-mark answer needs the causes of loss and matching practical ways to limit them.
Vitamin C is water soluble and easily destroyed by heat, oxygen and the enzyme oxidase released when cells are cut. It is lost by dissolving into cooking water, by prolonged cooking at high temperature, by cutting vegetables long before use and leaving them exposed to air, and by keeping them hot for a long time before serving.
Losses are reduced by preparing vegetables just before cooking, cutting them into larger pieces to reduce the cut surface, cooking quickly in a small amount of water (or by steaming, microwaving or stir-frying), serving promptly, and not adding bicarbonate of soda (which destroys vitamin C).
Markers reward at least two causes of loss (water solubility, heat, oxidation, leaching) and at least two valid prevention methods.
Related dot points
- Minerals as micronutrients: calcium, iron, sodium and other minerals, their functions, food sources and bioavailability, the effects of deficiency and excess, and the functions and importance of water in the diet.
A CCEA A-Level Nutrition and Food Science answer on minerals and water: the functions and sources of calcium, iron and sodium, mineral bioavailability and absorption, the effects of deficiency and excess, and the functions and importance of water in the diet.
- Protein as a macronutrient: amino acids, the distinction between essential and non-essential amino acids, high and low biological value protein, protein complementation, the functions and food sources of protein, and the consequences of deficiency and excess.
A CCEA A-Level Nutrition and Food Science answer on protein: its amino acid structure, essential and non-essential amino acids, high and low biological value, protein complementation, the functions and sources of protein, and the effects of deficiency and excess.
- Fats and lipids as a macronutrient: triglyceride structure, saturated, monounsaturated and polyunsaturated fatty acids, essential fatty acids and cholesterol, the functions and food sources of fat, and the dietary recommendations and health effects of different fats.
A CCEA A-Level Nutrition and Food Science answer on fats and lipids: triglyceride structure, saturated, monounsaturated and polyunsaturated fatty acids, trans fats, essential fatty acids, cholesterol, the functions and sources of fat, and the dietary recommendations.
- Nutritional requirements and current dietary recommendations for each life stage: pregnancy and lactation, infancy and weaning, childhood, adolescence, adulthood and the elderly, including how energy and key nutrient needs change and the dietary advice for each group.
A CCEA A-Level Nutrition and Food Science answer on nutritional needs through the life stages: pregnancy and lactation, infancy and weaning, childhood, adolescence, adulthood and the elderly, with the changing energy and nutrient needs and dietary recommendations for each group.
- The functional and chemical properties of nutrients in food: protein denaturation, coagulation and foaming, starch gelatinisation and dextrinisation, the caramelisation of sugar and the Maillard reaction, and how these properties are used in food preparation.
A CCEA A-Level Nutrition and Food Science answer on the functional and chemical properties of nutrients in food: protein denaturation, coagulation and foaming, starch gelatinisation and dextrinisation, caramelisation and the Maillard reaction, and how these are used in food preparation.
- Diet-related conditions of bone, teeth and blood: osteoporosis and the role of calcium and vitamin D, dental caries and the role of free sugars and fluoride, and iron-deficiency anaemia and the role of iron and vitamin C, with the dietary advice for each.
A CCEA A-Level Nutrition and Food Science answer on diet-related conditions of bone, teeth and blood: osteoporosis and calcium and vitamin D, dental caries and free sugars and fluoride, and iron-deficiency anaemia and iron and vitamin C, with the dietary advice for each.
Sources & how we know this
- CCEA GCE Nutrition and Food Science specification — CCEA (2016)
- Vitamin D and health (SACN report) — Scientific Advisory Committee on Nutrition (2016)