How does diet affect cancer risk, and what dietary advice can lower it?
Diet and cancer: the dietary and lifestyle factors that raise or lower cancer risk (red and processed meat, fibre, fruit and vegetables, alcohol, obesity and salt), the focus on bowel cancer, and the dietary advice for prevention.
A CCEA A-Level Nutrition and Food Science answer on diet and cancer: the dietary and lifestyle factors that raise or lower cancer risk (red and processed meat, fibre, fruit and vegetables, alcohol, obesity and salt), the link to bowel cancer, and the dietary advice for prevention.
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What this dot point is asking
CCEA wants you to discuss how diet and lifestyle affect cancer risk: the factors that raise risk (red and processed meat, low fibre, alcohol, obesity, salt) and those that lower it (fibre, fruit and vegetables), with bowel cancer as the key example, and the dietary advice for prevention.
Factors that raise and lower cancer risk
Factors that raise risk include a high intake of red and processed meat (processed meat such as bacon and ham is the strongest dietary link to bowel cancer), a low fibre intake, excessive alcohol (mouth, throat, liver, bowel and breast cancers), being overweight or obese (several cancers), and a high salt intake (stomach cancer).
Dietary advice for prevention
CCEA expects a balanced view: diet is one risk factor among many (including smoking, genetics and environment), and the evidence is about raising or lowering probability, not certainty. Current cancer-prevention guidance from bodies such as the World Cancer Research Fund underpins the recommendations.
Examples in context
Example 1. Five a day and wholegrains. A person who switches from white bread and few vegetables to wholegrain bread, pulses and at least five portions of fruit and vegetables markedly raises fibre, antioxidants and protective compounds. This speeds gut transit and supports cell protection, lowering bowel-cancer risk while also improving heart and weight outcomes, showing how one change helps several conditions.
Example 2. Cutting back on processed meat. A household that has a fry with processed meat most mornings reduces it to an occasional treat and replaces it with eggs, beans or fish. Lowering processed-meat intake below the 70 g guideline reduces a clear dietary risk factor for bowel cancer, applying the prevention advice in a realistic way.
Try this
Q1. Name the type of cancer most clearly linked to diet, and one food that increases its risk. [2 marks]
- Cue. Bowel (colorectal) cancer; processed (or red) meat increases the risk.
Q2. Explain how a high fibre intake may reduce the risk of bowel cancer. [2 marks]
- Cue. Fibre adds bulk and speeds gut transit, so carcinogens are in contact with the gut wall for less time and are diluted.
Q3. State the recommended maximum daily intake of red and processed meat. [1 mark]
- Cue. No more than about 70 g a day.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA AS 20196 marksDiscuss the dietary and lifestyle factors that affect the risk of developing cancer, and explain the advice given to reduce that risk.Show worked answer →
A 6-mark answer needs factors that raise risk, factors that lower it, and the dietary advice.
Several diet and lifestyle factors raise cancer risk. A high intake of red and especially processed meat is linked to bowel (colorectal) cancer. A low intake of dietary fibre is also linked to bowel cancer because fibre speeds the passage of waste through the gut and dilutes harmful substances. Excessive alcohol is linked to cancers of the mouth, throat, liver, bowel and breast. Being overweight or obese raises the risk of several cancers, including bowel and breast, and a high salt intake is linked to stomach cancer.
Factors that lower risk include a high intake of fruit and vegetables, which supply fibre, antioxidants and other protective compounds, and plenty of dietary fibre from wholegrains and pulses.
The advice is therefore to limit red and processed meat (no more than about 70 grams a day), eat at least five portions of fruit and vegetables and plenty of fibre, limit alcohol and salt, and maintain a healthy weight.
Markers reward at least two risk-raising factors, at least one protective factor, and clear advice with the meat and fruit-and-vegetable messages.
CCEA AS 20214 marksExplain how dietary fibre and a high intake of fruit and vegetables may help to reduce the risk of bowel cancer.Show worked answer →
A 4-mark answer needs the protective mechanisms of fibre and of fruit and vegetables.
Dietary fibre (NSP) adds bulk to the faeces and speeds the passage of waste through the large intestine. This reduces the time that any harmful or carcinogenic substances are in contact with the gut wall, and it dilutes them, which is thought to lower the risk of bowel cancer.
Fruit and vegetables supply additional fibre and a range of antioxidants and other protective compounds (such as vitamins C and A and plant chemicals) that help protect cells from damage. A diet high in both fibre and fruit and vegetables is therefore associated with a lower risk of bowel cancer.
Markers reward fibre adding bulk and speeding transit so carcinogens are in contact for less time and are diluted, and fruit and vegetables supplying fibre and antioxidants or protective compounds.
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Sources & how we know this
- CCEA GCE Nutrition and Food Science specification — CCEA (2016)
- Iron and health (SACN report on red and processed meat) — Scientific Advisory Committee on Nutrition (2010)