WHAT IS CANCER? WHAT CAUSES CANCER?

WHAT IS CANCER?

While cancer is often referred to as one illness, it is actually over a hundred different diseases. Many cancer cases are unique, and although there can be many different reasons for its development and many different ways it manifests itself, the way that cancer is formed is quite generic. According to the WHO: ‘Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms. One defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs. The process of the spread of cancer in the body is referred to as metastasis. Metastases are the major cause of death from cancer.’

Johannesburg-based dietitian Jenny Meyer points out that carcinogenesis, which is the origin or development of cancer, is a biological, multistage process that has three phases: initiation, promotion and progression. ‘A carcinogen is a physical, chemical or viral agent that induces cancer,’ she explains.

Initiation is when a cell’s DNA is changed so that the cell mutates. This change/mutation can either be spontaneous or triggered by a carcinogen. A single mutated cell is not dangerous and may simply die; however, it can lie dormant in the body for many years. During the promotion stage, the initiated mutated cell is stimulated to divide and reproduce many cells all with the same mutation. Like in initiation, the trigger can be natural or caused by a carcinogen. (Often initiators also act as promoters.) In the progression stage, the constant replicating mass of cells form tumours or invade the blood, like in the case of leukaemia. They then metastasize or spread from the primary tumour to other parts of the body, taking the place of normal tissue.  This is when secondary cancers are formed.

The American Cancer Society (ACS) explains that cancer starts when cells in a part of the body start to grow out of control, but cancer cell growth is different from normal cell growth. ‘Instead of dying, cancer cells continue to grow and form new, abnormal cells. Cancer cells can also invade (grow into) other tissues, something that normal cells cannot do. Growing out of control and invading other tissues are what makes a cell a cancer cell.’

WHAT CAUSES CANCER?

While abnormal cell DNA may be passed on genetically, the majority of DNA damage is caused by mistakes that happen while the normal cell is reproducing or by something in the environment. Sometimes the cause is something obvious like cigarette smoking or sun exposure, but generally it is difficult to know exactly what causes any one person’s cancer.

However, the ACS reckons that ‘non-inherited factors have a larger impact on cancer risk for the population as a whole. Avoiding the use of tobacco products and exposure to second-hand smoke, maintaining a healthy weight, staying physically active throughout life, and consuming a healthy diet can substantially reduce a person’s lifetime risk of developing or dying from cancer.’9 Thus, being overweight, inactive and/or unhealthy can be the trigger that causes mutation or DNA damage, which could lead to cancer. Meyer elaborates: ‘Chemicals or carcinogens, such as polycyclic aromatic hydrocarbons (PAH), N-nitroso compounds (NOC) and bisphenol A (BP-A), limited fruit and vegetable consumption, radiation, tobacco/smoking, malignant neoplasm, viruses and excess energy all contribute to carcinogenesis. Nutrition may modify this process at any stage and with thousands of chemicals existing in a normal diet, some better known than others, diets can be both inhibitors and enhancers of carcinogenesis.’

The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) concur. Human adults are made up of around ten trillion cells, which are renewed and replaced constantly. ‘About 5–10 per cent of cancers result directly from inheriting genes associated with cancer, but the majority involve alterations or damage accumulated over time to the genetic material within cells. The causes of damage are both endogenous (internal) and exogenous (environmental). Food, nutrition, and physical activity are important environmental factors in the development of cancer.’

The University of Texas MD Anderson Cancer Center also identifies unhealthy diets, physical inactivity and obesity as risk factors for cancer, along with ageing, tobacco, familial/genetic risks, excessive UV exposure, cancer-associated viral/bacterial infections, chronic inflammation and various environmental exposures to things like radon or radiation.

Meyer cites modern diets, chemicals, hormones and a more sedentary lifestyle. ‘Evidence suggests that almost one-third [approximately 30 per cent] of cancer deaths may be attributed to nutrition and lifestyle behaviours such as poor diet, physical inactivity, alcohol use and obesity. Tobacco use results in a further significant increase in cancer deaths [another 30 per cent].’ She believes that an estimated 50 to 70 per cent of cancer deaths are potentially preventable by simply decreasing high-risk behaviours.

In looking at risk factors tied to cancer in her book, Monica Fairall singles out alcohol, diet and nutrition, environmental toxins, exercise, genetics, hormones, radiation, smoking and tobacco, stress and psychological factors, and viruses. While these are all important contributors to cancer, my focus is on the diet and nutrition aspects, although they are all interconnected. As Fairall points out, ‘Conservative estimates link over 30 per cent of cancers to nutritional causes. Some observers put the figures as high as 60 per cent among women’s cancers, and 40 per cent of men’s cancers.’ 11 These dietary risks, according to Fairall, include a high intake of animal fats, not enough fibre, smoked, pickled and salt-cured foods, chemically coloured foods, artificial sweeteners and a heavy intake of refined sugars.

While it may be overwhelming to engage with all the different ways to improve your health, it is important that you do so.

There is a wealth of biological evidence that shows how food and nutrition, physical activity and body composition have the ability to influence several stages in the process of cancer development. In a 2007 report, the WCRF and the AICR unequivocally stated: ‘Nutrients and food constituents have effects that can either inhibit several events that lead to cancer or contribute to cancer development, by altering DNA itself, or by altering how the genetic message in DNA is translated. Physical activity and variations in body composition also appear to influence cancer risk. Indeed, overall dietary patterns can indirectly influence cell growth by way of changes in general metabolic, regulatory, and endocrine effects.’