Why does the body need water and dietary fibre, and what happens without them?
Water and dietary fibre (NSP): their functions in the body, sources, recommended intakes and the effects of having too little, including dehydration and the role of fibre in digestive health.
A focused answer on water and dietary fibre for OCR GCSE Food Preparation and Nutrition (J309), covering the functions of water, the signs of dehydration, the role of NSP fibre in digestion, good sources and recommended intakes.
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What this dot point is asking
OCR groups water and dietary fibre (NSP) alongside the macronutrients and micronutrients because the body needs both for health even though they are not energy-providing in the usual sense. You need their functions, sources, recommended intakes and the effects of having too little.
Water
The main functions of water are:
- Transport - water is the main part of blood and other body fluids, carrying nutrients to cells and waste away.
- Temperature control - sweating uses water to cool the body when it is hot.
- Chemical reactions - water is needed for digestion and for the reactions inside cells.
- Removing waste - waste products are dissolved in water and removed in urine.
- Lubrication and moisture - it keeps the skin, eyes and the linings of the gut moist.
Dehydration is when the body does not have enough water. Signs include dark, strong-smelling urine, headaches, tiredness, poor concentration, a dry mouth, thirst and dizziness. Severe dehydration is dangerous, especially for babies, the elderly and the unwell, who are most at risk.
Dietary fibre (NSP)
The functions of fibre are:
- Adds bulk to the food in the intestines and holds water, keeping the contents soft and easy to move along.
- Prevents constipation and keeps the gut muscles working, lowering the risk of bowel disorders such as diverticular disease and bowel cancer.
- Satiety - fibre-rich foods are filling, which helps control how much you eat and so helps manage body weight.
- Slows digestion of sugars and helps control blood glucose and blood cholesterol.
Increasing fibre in cooking
You can raise the fibre in a dish by choosing wholegrain instead of white versions (wholemeal flour, brown rice, wholemeal pasta), leaving edible skins on fruit and vegetables, adding beans and lentils to soups, stews and curries, and including extra vegetables. This is a common exam ask: how would you adapt a recipe to make it higher in fibre.
Try this
Q1. Give the recommended daily fibre intake for an adult. [1 mark]
- Cue. About 30 g a day.
Q2. Give two signs of dehydration. [2 marks]
- Cue. Any two of dark urine, headache, tiredness, dry mouth, thirst, dizziness.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20184 marksExplain why dietary fibre (NSP) is an important part of a healthy diet.Show worked answer →
A 4-mark question on the functions of fibre.
Fibre (non-starch polysaccharide, NSP) is not digested but adds bulk to food in the gut. This bulk holds water and keeps the contents of the intestines soft and moving, so it prevents constipation and helps the digestive system work smoothly.
Fibre also makes you feel full (satiety), which can help control body weight, and a high-fibre diet is linked to a lower risk of bowel disorders such as diverticular disease and bowel cancer, and helps control blood sugar and cholesterol.
Markers reward: fibre adds bulk, prevents constipation, aids healthy digestion, gives satiety and lowers the risk of bowel disease. Adults are advised to eat about 30 g a day.
OCR 20204 marksDescribe two functions of water in the body and explain two signs that a person is not drinking enough.Show worked answer →
A 4-mark structured question, two marks for functions and two for signs.
Functions (any two): water makes up the blood and other body fluids and transports nutrients and waste; it helps control body temperature through sweating; it is needed for chemical reactions in cells and digestion; it removes waste in urine; it keeps skin and the linings of the body moist.
Signs of not drinking enough (dehydration), any two: dark, strong-smelling urine; headaches; tiredness and poor concentration; dry mouth and lips; feeling thirsty; dizziness.
Markers reward two clear functions and two clear signs of dehydration. Adults need about 6 to 8 glasses (around 1.5 to 2 litres) of fluid a day, more in hot weather or when exercising.
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