While we can never prevent all bowel cancers, healthy lifestyle choices, are among the most recognised and manageable ways to reduce the prevalence of the disease, with around 54% of all bowel cancers thought to be preventable.
Smoking is thought to cause at least 8 out of every 100 bowel cancers. In Wales this would mean that 170 bowel cancers could be prevented if people just stopped smoking. The effect of smoking on bowel cancer risk is greater for women but is also shown for men.
Tobacco smoke contains over 7000 different chemicals, 70 of which are known to cause cancer. These include, lead, arsenic, benzene, hydrogen cyanide, ammonia and formaldehyde.
These chemicals directly damage DNA in cells that line the bowel, or via the blood stream following inhalation in the lungs. This damage can result in permanent changes called mutations that may give rise to cancer over time.
Current evidence suggests that there are no safe limits for drinking alcohol when it comes to cancer risk. Around 6 out of 100 bowel cancers are thought to be directly attributed to alcohol use.
These cancer-causing effects stem from the by-products, such as aldehydes, that are produced as the alcohol is broken down and removed from the body. It is the amount of alcohol that a person drinks over time and not the type of alcoholic beverage consumed that is important.
While links between alcohol use and bowel cancer risk have been demonstrated for both men and women, the risk appears greater for men, and may reflect the different ways alcohol is broken down between the genders.
To reduce the risk of bowel cancer from alcohol it is recommended that people keep drinking to a minimum and certainly not exceed the guidelines of 14 units or less per week, which are the same for both men and women.
People who both smoke and drink alcohol run a higher risk of developing cancer than people who alone either smoke or drank. It is proposed that alcohol makes it easier for carcinogens contained within tobacco smoke to cross the lining of the gastro-intestinal tract.
Research has consistently shown diets to be rich in fruit, vegetables and fibre, and in low red meat products, especially processed meats, protect against bowel cancer.
Health questionnaires sent out by Public Health Wales found more than 65% of all adults who responded, do not eat the recommended 5 portions of fruit and vegetable per day. In deprived areas this figure dropped to as low as 20%.
In 2016, The World Health Organisation categorised processed red meat as a Class I carcinogen. Meaning there is now enough evidence to make a direct link between the development of bowel cancer and high intake of foods such as sausages, bacon, ham, burgers and other processed meats on a regular basis.
Recommendations advise people not to eat more than 70g of processed or other red meats per day and where possible replace with white meats such as chicken and fish.
Other modifiable interventions that help prevent against bowel cancer include physical exercise and maintaining a healthy body weight.
Moderate intensity physical exercise is associated with lower incidence of bowel cancer and lower recurrence of the disease if diagnosed.
Moderate intensity exercise such as brisk walking or cycling is defined as an activity that will cause adults to get warmer, breath harder and increase heart rate, whilst being able to maintain a conversation.
Adult obesity has long been associated with an increased risk of bowel cancer
Obesity is an established risk factor for bowel cancer, including hereditable forms associated with Lynch Syndrome.
It is estimated that obesity increases the likelihood of developing bowel cancer in a person by up to 30% when compared to those of normal weight. The association between bowel cancer risk and obesity is greater in men.
Similar to most developed countries in the West, the number of people in Wales reported to be overweight or obese is on the rise, with almost 60% of all adults falling into one of these two categories.
Deprived areas again appear to be disproportionality affected, with 12% of more adults reported to be overweight than those in more prosperous communities.
While the link between obesity and bowel cancer has only been made for adults, it will be important to understand what effects the higher levels of childhood obesity in Wales may have on bowel cancer risk in later life. This will help develop and target future preventative strategies.
Blog Written by Dr Lee Campbell – SCIENCE PROJECTS AND RESEARCH COMMUNICATIONS MANAGER