Colorectal cancer is the third-most common cancer among Jamaican men. This cancer affects men more frequently than women. It is more frequent in countries that are industrialised, and is considered a cancer of the westernised lifestyle. The cancer develops slowly, over decades, from adenomatous polyps which are raised areas inside the bowel. The polyps have a predilection for the distal third of the large bowel, affecting the left side of the large intestine and the rectum.

Signs of colorectal cancer

Unfortunately, colorectal cancer shows symptoms when the disease is far advanced. These include a change in the timing or frequency of defecation or an unexplained change in the consistency of the stool. Blood, mixed with the stool or a mucous discharge, is a serious sign, and is highly significant in older persons. The sensation of incomplete evacuation of stool might be an important symptom of the presence of a tumour in the rectum. Anaemia (weak blood) of unknown origin, especially after age 55, is cause to investigate for right-sided colonic tumours.

Screening

Early detection of colorectal cancers can be achieved by examining the stool for occult blood and direct examination of the bowel using endoscopes such as the flexible sigmoidoscope and the colonoscope. Unfortunately, there is a low rate of participation in these tests because of their inconvenience and costs. However, the five-year survival for treatment of the cancer detected at stage one is over 90 per cent, compared with only five per cent for persons treated at stage four of the disease.

Causes

No one is absolutely clear about the causes of colorectal cancer, but there is abundant evidence that, in men, this cancer is associated with obesity and low-physical activity. It has been shown that high levels of abdominal fat which is demonstrated by increased waist size correlate with colon cancer especially in sedentary individuals. A diet high in the consumption of red meat or processed meats that contain nitrites and nitrates might put individuals at risk for colorectal cancer but this has not been confirmed.

High-risk diets

The western diet is thought to promote this cancer because of the inclusion of high levels of carcinogens (cancer-causing agents) as well as exclusion of anti-carcinogenic protective factors. Also, diets that cause obesity are believed to modify the individual's metabolic status in such a way as to make the large bowel susceptible to carcinogens.

Prevention

A varied diet, high in dietary fibre, fruits and vegetables to ensure adequate intake of folates, calcium, vitamin D, selenium and other phytochemicals, is thought to be protective. It is also recommended that red meat intake should be limited to less than four ounces daily and that fish should be included in the diet. Overall, men should try to maintain their normal body weight and take regular exercise.

Dr Pauline Williams-Green is a family physician and president of the Caribbean College of Family Physicians; email: yourhealth@gleanerjm.com.