The Effects of Nutrition and Exercise on Bowel Cancer Risk

Mug-shot-223x300Bowel cancer is one of the most common cancers in the world. A recent research report from the World Institute for Cancer Research has highlighted that obesity, processed meats, red meats, and alcohol may increase the risk of bowel cancer. In contrast, high fibre diets, physical activity, garlic and calcium may reduce the risk. There is also a suggestion that natural fruits, and foods containing folate, vitamin D and selenium may help reduce the risk.

I have a family medical history of bowel cancer. So when a 48-year-old mate of mine from University days recently died of bowel cancer, I made the decision to get a colonoscopy. The psychologically stressful test was physically harmless. I got the all clear from the Physician, a fellow masters athlete. He suggested that I come back in 5 years time and that my active lifestyle and healthy diet focused on fish, white meat, fruit and vegetables will protect me from bowel cancer well into older age.

The experience prompted me to do some ‘homework’ on bowel cancer and what affect diet and exercise may have on bowel cancer. I jumped onto the University library databases and typed in the keywords bowel cancer, exercise and nutrition. Up popped a major joint report from the World Cancer Research Fund and the American Institute for Cancer Research titled Food nutrition, physical activity and the prevention of cancer: a global perspective. The report developed a series of recommendations based on an a systematic review of the available research literature relating to exercise, nutrition and the risks of developing cancer. The results are summarised in the table below.

Table: Factors that modify the risk of colon and rectum cancers.

Strength of Research Evidenceh Increases Risk Decreases Risk
Convincing Evidence Red meat, processed meat, alcoholic drinks (men), body fatness, abdominal fatness Physical activity
Probable Evidence Alcoholic drinks (women) Foods containing dietary fibre, garlic, milk, calcium
Limited Evidence Foods containing iron, cheese, foods containing animal fat, foods containing sugars Non starchy vegetables, fruits (not including those preserved by salting or pickling), foods containing folate, selenium, and vitamin D, fish
Inconclusive Cereals and grains, potatoes, poultry, seafood, sugar, caffiene, tea, vitamins A, C and E, multivitamins, meal frequency and total energy intake

Factors increasing bowel cancer risk

  1. Obesity: Obese men may be 50% more at risk than lean men. In women the increased risk is not as great as it appears the female hormone oestrogen, even when taken in hormone replacement therapy or the oral contraceptive pill, may offer some protection. In both genders, increased abdominal fat as measured by waist circumferences and waist: hip ratio is associated with increased risk.
  2. Red and processed meat: A long term study conducted on 480,040 adults from 10 European countries over six years revealed that colorectal cancer risk increases with higher intakes of red and processed meats but not poultry and decreases with fish intakes. High intakes of iron as found in red meats was also associated with increased risk of bowel cancer.
  3. Alcohol: Although the evidence is stronger for men, the above study found higher risk of rectal cancer in bigger drinkers. Interestingly, beer drinking is a slightly greater risk than drinking wine. The greater risks were associated with alcohol intakes in excess of 30g/day (1 standard drink contains 10 grams of alcohol).

Factors decreasing bowel cancer risk

  1. Physical activity: All types of occupational and recreational activity appear to reduce the risk of bowel cancers. Importantly, research has suggested a dose-response association in both men and women. That is, the more exercise you do, the greater the benefit – great news for masters athletes. Specifically, the research suggested a protective effect of physical activity on both colon and pre- and post-menopausal breast cancer. While research to date  hasn’t nailed what is the optimal combination of type, intensity, duration, and frequency of exercise is best, the research concludes that moderate intensity activity (>4.5 MET) is more protective than light activities (<4.5 MET). Most sports training is well above these intensities.
  2. Fibre: Eating foods high in fibre reduces the risk of bowel cancer. It appears whole grains (bran and germs – e.g. rolled oats, oat bran, wheat germ, brown rice, wholemeal flour and bread) and fruit fibres have greater benefits than vegetable fibre.
  3. Calcium: Research has shown that calcium may bind with dangerous compounds that unbound may irritate the gut lining. Research has shown that both dairy products and calcium supplements decrease bowel cancer risk and prevent polyps developing.
  4. Fruit and vegetables: Most likely due to the antioxidants contained in these nutrients, research has shown lower incidence of bowel cancer in people eating fruit and vegetables. Folate has also been shown to reduce bowel cancer risk. Leafy green vegetables (like spinach and turnip greens), fruits (like citrus fruits and juices), and dried beans and peas are all natural sources of folate.
  5. Garlic: Has been shown to protect against bowel cancer.

Conclusion

My physician was right! Training regularly and eating a high fibre diet with plenty of fruit and vegetables, cereals and brans, combined with fish and chicken rather than red or processed meats will hold me in good stead to hold off the BIG C.

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