How does the body make EPA and DHA?

The body converts alpha-linolenic acid to EPA and then DHA by lengthening the chain and adding double bonds. The conversion is slow and inefficient, especially to DHA.

Why are EPA and DHA sometimes described as conditionally essential?

Conversion from alpha-linolenic acid is too limited to meet needs reliably. EPA and DHA are best supplied ready-made from oily fish.

What are eicosanoids?

Eicosanoids are hormone-like compounds made from fatty acids with 20 carbons. Prostaglandins, thromboxanes and leukotrienes are examples.

CCEA A-Level Nutrition and Food Science 3310

Protein

Topic overview Functions of protein Amino acids, biological value and complementation Animal and plant sources of protein Novel protein sources Nitrogen balance and protein requirements

Fat

Topic overview Functions of fat Structure of fats and fatty acids Saturated and monounsaturated fatty acids Omega-3, omega-6 and trans fatty acids Essential fatty acids

Carbohydrate

Topic overview Sources and functions of carbohydrate Intrinsic, extrinsic and non-milk extrinsic sugars Starch and resistant starch Non-starch polysaccharides and dietary fibre Blood sugar, glycaemic index and glycaemic load

Vitamins

Topic overview Vitamin solubility, absorption and bioavailability Vitamin A and beta-carotene Vitamin D and sunlight Vitamins E and K Thiamin, riboflavin and niacin Vitamin B6, vitamin B12 and folate Vitamin C and scurvy

Minerals

Topic overview Calcium and phosphorus Magnesium, sodium and potassium Iron and iron deficiency anaemia Iodine and fluorine Selenium and zinc Mineral bioavailability and absorption

Water and Other Fluids

Topic overview Functions and sources of water Nutritional benefits of other drinks Factors affecting hydration Dehydration and water intoxication

Nutrition Through Life

Topic overview Pre-conception and pregnancy nutrition Lactation and infant milk feeding Weaning and pre-school children School-age children and teenagers Nutrition for adult men and women Older adults and the frail elderly Dietary Reference Values and diet evaluation

Eating Patterns

Topic overview Food consumption trends and demographic change Social change, employment and leisure patterns Resources and availability of healthy food Food labels and advertising as barriers

Energy and Energy Balance

Topic overview Why the body needs energy Basal metabolic rate and physical activity level Energy EARs through life Energy balance and weight change

Overweight and Obesity

Topic overview BMI, waist circumference and measuring body fat Trends in childhood and adult obesity Barriers to achieving a healthy weight Health problems of excess weight Achieving a healthy weight in children and adults

Cardiovascular Disease

Topic overview Defining CVD and how atherosclerosis develops Non-modifiable risk factors for CVD Smoking, inactivity, alcohol, obesity and Type 2 diabetes Blood cholesterol, fatty acids and soluble fibre Hypertension, sodium, antioxidants and homocysteine Preventing CVD through diet and lifestyle

Cancer

Topic overview Cancer and how tumours develop Fat, salt and meat in cancer risk Wholegrains, fruit, vegetables and antioxidants Lifestyle factors in cancer risk Recommendations to reduce cancer risk

Type 2 Diabetes

Topic overview Definition and symptoms of Type 2 diabetes Risk factors for Type 2 diabetes Preventing Type 2 diabetes Managing Type 2 diabetes

Alcohol

Topic overview Units, energy and alcohol's link to obesity Alcohol, the heart and cancer Alcohol in pregnancy and the developing baby Nutritional effects of heavy drinking

Physical Activity

Topic overview UK physical activity guidelines Activity, heart health and energy balance Bone, joint, muscle and mental health benefits

Food Security and Food PovertyOption A

Topic overview Food security and the threat from climate change Land degradation and population growth Food poverty as a global issue Food poverty in the UK and Northern Ireland Food banks, FareShare and the Trussell Trust

Food SustainabilityOption A

Topic overview Animal farming, climate change and natural resources Local and seasonal food Organic farming and the environment Fairtrade and producer countries Red Tractor, NI Beef and Lamb, LEAF and Conservation Grade Carbon labels, Rainforest Alliance, MSC and green claims

Food WasteOption A

Topic overview Environmental and ethical impact of food and packaging waste Waste from primary producers and food manufacturers Waste from retailers and consumers WRAP, the Courtauld Commitment and Love Food Hate Waste NI

Changing Consumer BehaviourOption A

Topic overview Advice for sustainable food choices Barriers to sustainable food choices Environmental and social cost of supermarket shopping

Food Safety Through the Food ChainOption B

Topic overview WHO and shared responsibility for food safety Animal and plant health risks The Food Standards Agency and DAERA GMP, quality assurance standards and traceability HACCP in food-serving establishments Hygiene ratings, food law inspections and EHPs

Microbiological ContaminationOption B

Topic overview Salmonella and Campylobacter Listeria and Escherichia coli High-risk foods for food poisoning Microbial control by producers and manufacturers Microbial control in catering and at home

Chemical ContaminationOption B

Topic overview Acrylamide in cooked foods Arsenic in rice Bisphenol A and dioxins Mercury, lead and cadmium in food

Food AdditivesOption B

Topic overview Additive regulation and E numbers Food colours and flavour enhancers Intense and bulk sweeteners Preservatives, nitrites and sulphites

Food AllergensOption B

Topic overview Why food allergies are increasing Allergen labelling and information rules The FSA's work on allergy and intolerance

Food Safety Controls and LegislationOption B

Topic overview EFSA and food risk assessment General food hygiene under Regulation 852/2004 Regulation 853/2004 and official controls

Research Skills

Topic overview Primary and secondary research Questionnaires and interviews Food diaries, observation and sensory evaluation Sampling and research ethics Evaluating and referencing sources Analysing and presenting data

Fat

Essential fatty acids

3 things to know
AS 1

Overview

Linoleic and alpha-linolenic acids, EPA and DHA, eicosanoids, the omega-6 to omega-3 balance, deficiency and how vegans can obtain omega-3.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is an essential fatty acid?

Key term

Name the two essential fatty acids.

Key term

Why can the body not make omega-3 and omega-6 fatty acids?

Questions from this subtopic

Each one with the model answer underneath.

1
What is an essential fatty acid?
Model answer
An essential fatty acid is one the body needs but cannot make. Essential fatty acids must be supplied by the diet.
2
Name the two essential fatty acids.
Model answer
The essential fatty acids are linoleic acid, an omega-6, and alpha-linolenic acid, an omega-3.
3
Why can the body not make omega-3 and omega-6 fatty acids?
Model answer
Human cells cannot insert a double bond near the methyl end of a fatty acid chain. Fatty acids with a double bond at the omega-3 or omega-6 position must come from food.
4
How does the body make EPA and DHA?
Model answer
The body converts alpha-linolenic acid to EPA and then DHA by lengthening the chain and adding double bonds. The conversion is slow and inefficient, especially to DHA.
5
Why are EPA and DHA sometimes described as conditionally essential?
Model answer
Conversion from alpha-linolenic acid is too limited to meet needs reliably. EPA and DHA are best supplied ready-made from oily fish.
6
What are eicosanoids?
Model answer
Eicosanoids are hormone-like compounds made from fatty acids with 20 carbons. Prostaglandins, thromboxanes and leukotrienes are examples.

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Protein

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