How does diet cause or prevent disease, and what dietary changes reduce the risk?
The relationship between diet and the major diet-related conditions and diseases - obesity, coronary heart disease, type 2 diabetes, dental caries, bowel disorders and bowel cancer, osteoporosis, anaemia and hypertension - including the dietary causes and the dietary changes that reduce the risk.
An SQA Higher Health and Food Technology answer on diet-related diseases, covering the dietary causes of and dietary changes for obesity, coronary heart disease, type 2 diabetes, dental caries, bowel disorders, osteoporosis, anaemia and hypertension.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
The SQA wants you to link diet to specific diseases - to explain the dietary cause of each condition and the dietary changes that reduce the risk. Higher rewards a clear mechanism (for example saturated fat to cholesterol to narrowed arteries) and named, justified changes.
Obesity
The causes are a diet high in fat and free sugars (energy-dense), large portions and excess calories, with low activity. Obesity matters because it is a gateway, raising the risk of coronary heart disease, type 2 diabetes, hypertension and some cancers. Changes: reduce energy intake, eat more filling, lower-energy foods (fruit, vegetables, fibre), and be more active to restore energy balance.
Coronary heart disease (CHD)
Dietary changes: reduce saturated fat (swap to unsaturated oils and lean cuts) to lower cholesterol; eat oily fish for omega-3; cut salt to lower blood pressure; eat more fibre (especially soluble fibre such as oats), fruit and vegetables; and control weight.
Type 2 diabetes
Dietary changes: lose excess weight, cut free sugars and refined carbohydrate, and choose high-fibre starchy foods that release glucose slowly to keep blood glucose steady.
Dental caries
Dental caries (tooth decay) is caused by free sugars: bacteria in dental plaque ferment sugar to acid, which dissolves tooth enamel. Both the amount and especially the frequency of sugary food and drink matter - frequent snacking keeps the mouth acidic. Dietary changes: reduce free sugars and how often they are eaten, choose water or milk over sugary drinks, and benefit from fluoride.
Bowel disorders and bowel cancer
A diet low in NSP (fibre) is linked to constipation, diverticular disease and a raised risk of bowel cancer, because fibre adds bulk and speeds the passage of waste through the gut, reducing the time the gut lining is in contact with harmful substances. A high intake of red and processed meat also raises bowel cancer risk. Dietary changes: eat more wholegrain foods, fruit, vegetables and pulses for fibre, drink enough fluid, and limit processed meat.
Osteoporosis
Diet contributes when calcium intake is low over a lifetime and when vitamin D is short (vitamin D is needed to absorb calcium), so peak bone mass is never reached or bone is lost faster. Dietary changes: ensure enough calcium (dairy or fortified alternatives, green vegetables) and vitamin D (oily fish, sunlight, supplements), starting in youth when bone is being built.
Anaemia
Iron-deficiency anaemia results from too little iron to make haemoglobin, so the blood carries less oxygen - causing tiredness, pallor and breathlessness. Groups at risk include teenage girls and pregnant women. Dietary changes: eat more iron-rich foods (lean red meat, pulses, dark green vegetables, fortified cereals) and take them with a vitamin C source to aid absorption.
Hypertension
Hypertension (high blood pressure) raises the risk of heart disease and stroke. The main dietary cause is excess salt (sodium), which makes the body retain fluid and raises blood pressure; being overweight adds to it. Dietary changes: cut salt (less processed food, no added salt), lose excess weight, and eat more fruit and vegetables (which supply potassium).
Examples in context
Example 1. Sugar reduction and reformulation. Manufacturers have cut sugar in soft drinks, cereals and yoghurts to tackle obesity, type 2 diabetes and dental caries - diet-disease knowledge driving reformulation and policy such as the soft drinks levy.
Example 2. Salt reduction targets. Producers have lowered salt in bread, processed meat and ready meals to reduce population blood pressure and the burden of heart disease and stroke - a response to the sodium-hypertension link.
Try this
Q1. Name the diet-related disease caused mainly by free sugars fermenting to acid in the mouth. [1 mark]
- Cue. Dental caries (tooth decay).
Q2. State two dietary changes that would reduce a person's risk of coronary heart disease. [2 marks]
- Cue. Reduce saturated fat; cut salt; eat more oily fish or fibre; control weight (any two).
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 Higher (specimen)6 marksExplain how diet contributes to coronary heart disease and describe four dietary changes that would reduce a person's risk.Show worked answer →
A 6-mark answer needs the disease mechanism plus four justified dietary changes.
Mechanism: a diet high in saturated fat raises blood LDL cholesterol. Cholesterol is deposited in artery walls as fatty plaques (atheroma), narrowing the coronary arteries that supply the heart muscle. This restricts blood and oxygen to the heart, causing angina, and a blocked artery causes a heart attack. A high-salt diet adds to the risk by raising blood pressure, and being overweight strains the heart.
Four dietary changes (each justified):
- Reduce saturated fat (swap butter and fatty meat for unsaturated oils and lean cuts) to lower LDL cholesterol.
- Eat more oily fish for omega-3 fatty acids, which support heart health.
- Cut salt to lower blood pressure.
- Eat more fruit, vegetables and fibre (especially soluble fibre such as oats), which help lower cholesterol and aid weight control.
Markers reward the cholesterol-atheroma-narrowing mechanism and four correct, justified changes (reduce saturated fat, reduce salt, more oily fish, more fibre/fruit/vegetables, control weight).
SQA Higher (past paper style)5 marksCompare the dietary causes of type 2 diabetes and dental caries, and state one dietary change that would help reduce the risk of each.Show worked answer →
A 5-mark compare answer should treat each condition's cause and give a change for each.
Type 2 diabetes: linked to being overweight or obese (often from a diet high in fat and free sugars and excess calories). Excess body fat makes the body's cells less responsive to insulin (insulin resistance), so blood glucose stays high. A dietary change: lose excess weight and cut free sugars and refined carbohydrate, choosing high-fibre starchy foods that release glucose slowly.
Dental caries: caused by free sugars. Mouth bacteria ferment sugar to acid, which dissolves tooth enamel; frequent sugary snacks and drinks keep the mouth acidic. A dietary change: reduce the amount and especially the frequency of free sugars, and choose water or milk instead of sugary drinks.
Comparison point: free sugars feature in both, but diabetes is driven mainly by overall excess energy and weight, whereas caries is driven by the frequency of sugar contact with the teeth.
Markers reward correct causes for each, one workable change each, and a genuine comparison.
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