Dehydration is a state in which the body loses more water than it takes in. Body fluids become more concentrated and normal functions are impaired.

A 70 kg runner weighs 68.6 kg after a race. What percentage of body mass has been lost, and what does this suggest?

The runner has lost 2% of body mass, enough to impair performance. The working is (70 − 68.6) ÷ 70 × 100 = 2%.

What are the effects of severe dehydration?

Severe dehydration causes dizziness, confusion, a rapid heart rate and low blood pressure. Urine output falls sharply, and without treatment severe dehydration can lead to collapse and death.

Why does dehydration cause a fast heart rate and low blood pressure?

Water loss reduces the volume of blood plasma. The heart beats faster to maintain blood flow, but blood pressure still falls.

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

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Carbohydrate

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Water and Other Fluids

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Nutrition Through Life

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Eating Patterns

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Energy and Energy Balance

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Overweight and Obesity

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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

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Food Security and Food PovertyOption A

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Food SustainabilityOption A

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Food WasteOption A

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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

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Food AllergensOption B

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Food Safety Controls and LegislationOption B

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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

Water and Other Fluids

Dehydration and water intoxication

3 things to know
AS 1

Overview

The signs, effects and treatment of dehydration and heat stroke, water intoxication and who is at risk, and a worked body mass loss calculation.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Define dehydration.

Key term

What are the early signs of dehydration?

Key term

How does mild dehydration affect performance?

Questions from this subtopic

Each one with the model answer underneath.

1
Define dehydration.
Model answer
Dehydration is a state in which the body loses more water than it takes in. Body fluids become more concentrated and normal functions are impaired.
2
What are the early signs of dehydration?
Model answer
Early signs of dehydration include thirst, dark urine, headache and tiredness. A dry mouth, dry lips and dry eyes are also common.
3
How does mild dehydration affect performance?
Model answer
A loss of about 2% of body mass as water can impair physical performance. Mild dehydration can also reduce concentration and alertness.
4
A 70 kg runner weighs 68.6 kg after a race. What percentage of body mass has been lost, and what does this suggest?
Model answer
The runner has lost 2% of body mass, enough to impair performance. The working is (70 − 68.6) ÷ 70 × 100 = 2%.
5
What are the effects of severe dehydration?
Model answer
Severe dehydration causes dizziness, confusion, a rapid heart rate and low blood pressure. Urine output falls sharply, and without treatment severe dehydration can lead to collapse and death.
6
Why does dehydration cause a fast heart rate and low blood pressure?
Model answer
Water loss reduces the volume of blood plasma. The heart beats faster to maintain blood flow, but blood pressure still falls.

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