March is identified as Colorectal Cancer Awareness Month.
There is deep concern among gastroenterologists, surgeons and oncologists over the rising incidence of colorectal cancer in younger people around the world. This phenomenon was first noted in the US, but is now becoming evident in South Africa too.
Colorectal cancer is the third most common cancer among women and second only to prostate cancer in men. Once more common in seniors, why is it becoming more common in younger people, and particularly men of black ethnicity in SA?
Also, colon cancer used to be rare in rural Africa. It was Ugandan-based surgeon Dr Denis Burkitt who proposed a reason in the early 1950s – protection from the high amount of dietary fibre in traditional diets. As Western diets have become increasingly refined, the protective effect of fibre is reduced. But it was in 2015 that the International Agency for Research on Cancer (an agency of the WHO) announced that processed meats are carcinogenic to humans. This statement was based on the review of over 800 published studies. At the same time it classified unprocessed red meat as “probably” carcinogenic. Processed meat includes cured, salted, smoked, fermented, or otherwise-altered products to improve preservation or flavour. Other dietary factors include alcohol and high dietary saturated fat. Colon cancer is also associated with obesity, inactivity and smoking, all common denominators of an unhealthy lifestyle.
Various familial conditions predispose people to colon cancer, but by far the most common factors are lifestyle-related.
What factors have been shown to reduce the risk? Regular exercise of four or more hours per week reduces the risk by around 50%. Regular use of aspirin and anti-inflammatory medicines reduces the risk by 20 to 40%. Numerous dietary factors can reduce the risk. The 100 000 strong, long term Adventist Health Studies showed lower incidences in vegetarians and vegans.
Mediterranean and DASH diets, both rich in plants and minimal red meat have shown protection from colorectal cancer. Plant proteins also show protective effect. High-fibre foods are fruits, vegetables, legumes, whole grains and nuts. These same foods are rich in phytonutrients, antioxidants, poly-unsaturated fats and magnesium, which all contribute to lower risks of colorectal cancer. High-fibre diets also improve the number and diversity of intestinal micro-organisms, again reducing risks of colorectal cancer.
How can we screen for the development of colorectal cancer? The gold standard is the colonoscopy. This is done every 10 years starting from the age of 50. However, if there is a family history of colorectal cancer or inflammatory bowel disease it should be started earlier, even at 35 years of age in some cases. The Cancer Association of South Africa also provides Faecal Occult Blood home stool test kits, which are less invasive, but also not as accurate.
So, colorectal cancer is becoming more common in younger people. Although genetic factors play a role, lifestyle factors are by far the more important factor. These include lack of exercise, smoking and alcohol use and the Western refined diet high in saturated fats and processed red meat, deficiencies in protective fibre, antioxidants, phytochemicals, and minerals. Choices can influence that risk.
- This health column is written by Dr Dave Glass, a retired obstetrician/gynaecologist living in Somerset West for just over a year. He is also chairperson of the South African Lifestyle Medicine Association (Salma).
- Glass, with an MBChB, FCOG(SA) and DipIBLM, has a passion for preventing and addressing the root causes of chronic diseases such as diabetes, heart disease, auto-immune diseases, obesity, dementia and cancer.
