Lifestyle Risk factors – how to reduce your risk of bowel cancer?
Risk factors other than family history can play a more important role in the development of bowel cancer. The main risk factor for bowel cancer is increasing age. Only 7% of bowel cancer occurs before the age of 50 years. However, even if you have a family history or other genetic risk of bowel cancer, this risk can be reduced by leading a healthy lifestyle. This kind of healthy lifestyle can also reduce your risk of heart disease, stroke and other cancers. It has been recently estimated that approximately 70% of colorectal cancer could be avoided by changes in lifestyle in Western countries.
A good further source of information about dietary and other lifestyle related risk factors is available from Cancer Research UK at http://www.cancerresearchuk.org/cancer-info/cancerstats/types/bowel/riskfactors/bowel-cancer-risk-factors
Summary: A diet high in red meat and animal fat and low in fruit and vegetables increases your risk of bowel cancer. So if you want to reduce your risk of bowel cancer, whether or not you have a genetic risk, eat 5 pieces of fruit or vegetables daily, plenty of fibre, and don’t eat too much processed or red meat.
Putative anti-carcinogenic mechanisms of dietary fibre within the bowel include: the formation of short-chain fatty acids from fermentation by colonic bacteria; the reduction of secondary bile acid production; the reduction in intestinal transit time and increase of faecal bulk; and a reduction in insulin resistance. In the European Prospective Investigation into Cancer and Nutrition (EPIC) study after an average 6.2 years of follow-up, and 1,721 colorectal cancer cases, a 21% reduced risk amongst participants in the highest intake quintile was observed when compared against the lowest intake group. These results support our previous conclusion, of the potential of reducing colorectal cancer incidence by increasing fibre intake from cereal, fruit, and vegetable food sources.
Red and processed meat
In the EPIC study high intake of red or processed meat may increase risk by 71%. The mechanisms underlying the association between colorectal cancer risk and high intake of red and processed meat are uncertain. Controlled human intervention studies have raised the possibility that the endogenous nitrosation that arises from ingestion of heme iron but not of inorganic iron or protein may account for the increased risk associated with red and processed meat consumption. Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAH) in diet may pose a potential risk of cancer to humans, depending on the extent to which the compounds are activated in vivo by metabolic enzymes. HCAs are formed as a byproduct of reactions during the cooking of meat, poultry, and fish at high temperatures, such as pan-frying or grilling with charcoal or on a gas grill; PAHs are formed in grilled and barbecued meat and in cured, processed foods. It has been suggested that processed meat intake has a stronger association with colorectal cancer than red meat intake.
Folate and selenium
Folate (a water-soluble B vitamin) appears to protect against bowel cancer, but it remains unclear whether the same level of benefit is derived from dietary folate (from food, particularly fruit and vegetables) and synthetic folate (folic acid supplements). Selenium can be obtained in food (particularly brazil nuts) and supplements; evidence for its effect on bowel cancer risk is mixed. The WCRF/AICR 2010 Report concluded that “Evidence for foods containing folate… and selenium… is less consistent and no conclusion could be drawn”.
Some experts have proposed that folate plays a dual role in bowel cancer in which moderate dietary intake before development of pre-cancerous adenomas reduces risk of adenoma development, but increased folate intake once adenomas have developed increases risk of cancer. Data from interventional studies indicate that folate supplementation decreases colonic mucosal cell proliferation . A large prospective study showing a 31% reduction in bowel cancer risk for people with the highest overall folate intake 12-16 years before diagnosis, but no effect of intakes in the more recent past.
The US Government was sufficiently convinced of the health benefits (and absence of risk) from folic acid that it introduced mandatory folic acid fortification of grain products in 1997, and a recent large cohort study found that 8.5 years on, higher total folate intake (including intake specifically from supplements) was associated with a decreased bowel cancer risk. There is some evidence that it is better to take folic acid in its natural form rather than as supplements i.e. tablets.
A 2011 meta analysis found men with the highest concentrations of selenium in the blood had 32% lower bowel cancer risk compared with men with the lowest concentrations, but found no association between selenium level and bowel cancer risk in women.3A 2004 pooled analysis found a similar level of risk reduction for both sexes combined.
Body weight and Obesity
Obesity is associated with an increased risk of colon cancer, particularly for men. Meta analyses show the risk of colon cancer increases by an estimated 24-30% per 5kg/m2 increase in body mass index (BMI) for men. In comparison to healthy-weight men (BMI less than 25 kg/m2), overweight men (BMI 25-29.9kg/m2) have a 23% higher risk of colon cancer, and obese men (BMI 30kg/m2 or more) have a 53% higher risk. The association is weaker in women, with colon cancer risk increasing by 9-12% per 5kg/m2 BMI increase, and the association proving non-significant in one meta analysis.
Larger waist size has been associated with increases in colon cancer risk in men (33% risk increase per 10cm waist circumference increase) and women (16% risk increase per 10cm waist circumference increase), as has increasing waist-to-hip ratio in both men (43% risk increase per 0.1-unit increase in ratio) and women (20% risk increase per 0.1 unit increase in ratio).
Higher BMI is linked less strongly to higher rectal cancer risk: a 5kg/m2 BMI increase is associated with a 9-12% higher rectal cancer risk for men (obese men have a 27% higher rectal cancer risk than healthy-weight men), but with no effect on rectal cancer risk in women
Regular physical activity can reduce your risk of bowel cancer, this is clearly shown in many studies. We would recommend 2-3 30 minute sessions per week of dedicated exercise (rather than more ‘passive’ exercise such as being busy at work!).
The relationship between physical activity and a reduced risk is one of the most consistent findings in epidemiologic literature.
Other risk factors
Not smoking and drinking less than the upper recommended limit of normal (less than 21 units for men and less than 14 units for women) may also be helpful.
- Lifestyle and Reducing your Risk (familyhistorybowelcancer.wordpress.com)
- Colorectal Cancer Aetiology (familyhistorybowelcancer.wordpress.com)
- Physical activity and exercise protect against bowel cancer – Cancer Research UK – Science Update blog (familyhistorybowelcancer.wordpress.com)
- Halving red meat consumption would slash heart disease and bowel cancer… and cut our carbon footprint (dailymail.co.uk)
- Study to test spice curcumin’s ability to fight bowel cancer (familyhistorybowelcancer.wordpress.com)
- Dietary fibre, whole grains, and a reduced risk of colorectal cancer: systematic review and meta-analysis (familyhistorybowelcancer.wordpress.com)