What are the different types of carbohydrate, what do they do, and why does the type we eat matter for health?
The function and dietary sources of carbohydrate, including starch, sugars and dietary fibre (NSP), and the effects on health of eating too much sugar or too little fibre.
An SQA National 5 Health and Food Technology answer on carbohydrate, covering the functions and sources of starch, sugars and dietary fibre (NSP), and the health effects of eating too much sugar or too little fibre.
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What this dot point is asking
The SQA wants you to know the three types of carbohydrate (starch, sugars and dietary fibre), state what each does, name foods that supply them, and explain the health effects of eating too much sugar or too little fibre.
The three types of carbohydrate
NSP stands for non-starch polysaccharide, the scientific name for most dietary fibre.
Functions and sources
Starch provides energy. Because it is digested slowly, it keeps you feeling full for longer and avoids a sharp rise and fall in blood glucose. Sources include bread, pasta, rice, potatoes, breakfast cereals and oats.
Sugars also provide energy, but quickly. Sources include table sugar, sweets, chocolate, cakes, biscuits, fizzy drinks, and the natural sugars in fruit and milk. Dietary advice separates free sugars (added sugars and the sugar in juice, honey and syrups), which should be limited, from the sugars naturally locked inside whole fruit and milk.
Dietary fibre (NSP) is not a source of energy because it is not digested. Its functions are to add bulk to the gut contents, to hold water and to help the muscles of the intestine push waste through, keeping the bowel regular. It also helps you feel full so you are less likely to overeat. Sources include wholemeal bread, wholegrain cereals, oats, beans, lentils, fruit and vegetables (especially with skins on).
Too much sugar
Too little fibre
Examples in context
Example 1. An athlete before training. A runner eats a bowl of porridge a couple of hours before a session. The starch is digested slowly and gives a steady release of energy through the run, which is better than a sugary snack that would give a quick rise then a dip.
Example 2. Helping an older adult avoid constipation. An older adult who often gets constipated is advised to eat more wholegrain cereal, fruit and vegetables and to drink more water. The extra fibre adds bulk and the water keeps it soft, so the intestine can move waste through more easily.
Try this
Q1. Name the type of carbohydrate that gives a slow release of energy, and one food that supplies it. [1 mark]
- Cue. Starch, from a food such as pasta, bread, rice or potatoes.
Q2. State one health problem linked to a diet that is too low in fibre. [1 mark]
- Cue. Constipation (also acceptable: bowel disorders or higher risk of bowel cancer).
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 style4 marksDescribe the function of dietary fibre (NSP) in the diet, and explain two effects on health of a diet that is low in fibre.Show worked answer →
A 4-mark answer needs the function plus two health effects, so plan one or two function marks and two effect marks.
Function. Dietary fibre (NSP) is not digested. It adds bulk to the contents of the gut, holds water and helps the muscles of the intestine push waste through. This keeps the bowel working regularly.
Effect 1. A diet low in fibre can cause constipation, because there is not enough bulk for the intestine to move waste along easily.
Effect 2. A long-term low-fibre diet is linked to bowel disorders such as diverticular disease and is associated with a higher risk of bowel (colorectal) cancer.
A further point that scores is that fibre helps a person feel full (satiety), so a low-fibre diet can make it easier to overeat and gain weight.
Markers reward a clear function and each valid health effect. Saying fibre "gives energy" is wrong: fibre is not digested and is not a source of energy.
SQA N5 style3 marksExplain three effects on health of eating too much sugar.Show worked answer →
This is an explain question worth 3 marks, so give three separate health effects, each with a brief reason.
Effect 1. Too much sugar can lead to dental caries (tooth decay), because bacteria in the mouth use sugar to make acid that attacks tooth enamel.
Effect 2. Sugar is high in energy, so eating more than the body uses leads to the extra energy being stored as fat, which can cause a person to become overweight or obese.
Effect 3. Being overweight and a sugary diet raise the risk of developing type 2 diabetes, where the body can no longer control blood glucose properly.
A further valid point is that sugary foods and drinks often supply energy but few other nutrients, so they can crowd out more nutritious foods.
Markers reward each distinct effect with its reason. Listing the same idea twice (for example "tooth decay" and "cavities") counts once.
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Sources & how we know this
- SQA National 5 Health and Food Technology Course Specification — SQA (2017)
- British Nutrition Foundation - Carbohydrate — British Nutrition Foundation (2023)