Cancers involving the colon, rectum, breast, prostate, ovary and endometrium tend to be linked to diseases of affluence, whereas those affecting the esophagus, stomach and mouth are often linked to poor diet. The most established cause of cancer is tobacco, but while we can give up smoking, we cannot give up eating!
Some Statistics
Cancer is a major global cause of mortality exceeded only by cardiovascular disease. The number of cases of cancer in the developing world looks set to increase by 73% and in the developed world by 29% over the next 15 to 20 years, because of the ageing population.
Dietary factors account for roughly one third and one fifth of cancers in developed and developing countries, respectively. This is a significant proportion, but it is difficult to link cause and effect precisely. One interesting observation is that the incidence of cancer changes as populations move between countries and then adopt new dietary and lifestyle patterns (1).
The problem is that cancer is not a single disease, it is a condition - triggered by the imperfections within our DNA, found in all tissues and all cells. There is no single cause and no single cure. Prevention is better than cure, but once again, there are no miracle measures to protect us from the wear and tear of getting old. An increased risk from cancer is one of of the consequences of ageing, as our DNA become less efficient at replicating itself during cell division. We need to understand more about what triggers this process to prevent it spinning out of control during the early development of cancerous tissues.
What Are The Main Risk Factors?
Good quality nutritional research requires evidence of peer-reviewed articles published in well-known journals so that the scientific community can see whether contributors have an objective point of view, rather than a vested interest in a particular product linked to the outcomes of research. This limits the publication of evidence which might otherwise mislead the general public, some of whom may be vulnerable to claims for miracle cures and linked to "healthy foods" and supplements.
Based on this rationale, the World Cancer Research Fund (1) has identified the following shortlist of dietary factors having a strong link to increasing the risk of cancers. The factors include:
- being overweight or obese
- excess or regular consumption of alcoholic beverages
- consuming aflatoxins from mouldy nuts and cereals
- heavily salted foods including fish
- high consumption of processed foods such as sausages and burgers
While much of the evidence on diet and cancer is still evolving, the media are often too quick to seize on headline grabbing news, which only dents the reputation of researchers trying to unravel a disease with multifactorial origins. Nevertheless, the majority of evidence shows that modifications in diet could significantly influence the incidence of cancers (2).
The maintenance of healthy body weight, along with the consumption of fruit, vegetables and whole grain cereals all appear to reduce cancer risk. Eating more dietary fibre, less total fat and saturated fat is also good advice. Increased consumption of antioxidant vitamins A, beta-carotene, C and E - together with vitamin D, folic acid and the minerals selenium and calcium, all provide a measure of protection (3).
The mechanisms behind these associations are complex, but there is now strong evidence that some of these nutrients act by counteracting oxidative damage in cells caused by molecules called free radicals produced as a natural waste product of cellular respiration. This oxidative damage and the generation of free-radicals attack key molecules such as DNA, protein and lipids, involved in the initiation and spread of cancer.
New Research
Non - nutrient components of food such as phytochemicals (e.g. polyphenols) are widespread in plants and they contribute to the flavour and colour of many fruits and vegetables. The commonest polyphenols are the flavonoids found in flowers, leaves, roots, tubers, herbs, spices, tea, coffee - and red wine! The anti-tumour properties of several phytochemicals are currently being investigated (4).
If there was just one piece of good advice it would be to be to plan your meals in modest proportions with colour and freshness in mind, and remember that whole grains count as yellow - just like the sunshine (and U-V) you also need during your regular daily exercise!
References:
- World Cancer Research Fund (1997) Food, Nutrition & the Prevention of Cancer: A Global Perspective. Washington DC. WCRF.
- UK Department of Health (1998) Nutritional Aspects of the Development of Cancer. Report on health and Social Subjects 48. London TSO.
- Cummings J.H. & Bingham S.A. (1998) Diet and the Prevention of Cancer. British Medical Journal 317, 1636-1640.
- Meskin M.S. et al (2002) Phytochemicals, Mechanisms of Action. pp 1-203 Florida CRC Press.
Allan Johnson - With 26 years experience in the field of Education I enjoy sharing my interest in things scientific, whether they crawl, glow in the dark ...
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