SOUNDBITES Paula MeeEvery time a cell in our body divides, it must copy the DNA it contains as accurately as possible. However, we're only human and mistakes are made - mistakes that can lead to the uncontrolled growth of cancerous cells.
When our immune system is working well, it can spot cancerous cells early on and kill them but if our immune system is compromised (due to stress, poor nutrition, HIV, etc) the incidence of cancers increases very significantly.
It's estimated that more than 30 per cent of all cancers are related to dietary factors. The health philosophy that prevention is better than cure holds true, particularly for cancer when the treatments can nearly be as distressing as the disease itself.
On a brighter note, there is increasing recognition that substances in the diet have real potential to prevent cancer and this body of evidence continues to grow. There are now more than 200 studies demonstrating the disease-fighting ability of phytochemicals which are found in fruits, vegetables and grains.
Scientists continue to identify and explore these powerful phytochemicals and antioxidants which mop up free radicals that cause tissue damage and disease. So far it remains unclear whether it's an individual phytochemical or a combination of these plant chemicals that lowers the risk of cancer.
Take prostate cancer as an example. The risk of prostate cancer drops for men who eat tomato products (tomato-based pasta sauces, tomato juice, tomato purees and ketchups). Lycopene, a carotenoid found in tomatoes, was thought to be the protective phytochemical. While tomato products have a significant impact on reducing the risk of cancer, some scientists have not seen a significant benefit from lycopene alone. It appears that tomato-based foods are the key to cancer prevention, not a lycopene supplement.
This isn't all that surprising as past experience has taught us that single nutrients or a few nutrients in a supplement does not give the same effect as eating whole foods.
Remember beta-carotene? For years, scientists noted that diets rich in foods containing beta-carotene (carrots and other brightly coloured fruit and veg) reduced the risk of many types of cancer, including lung cancer in smokers.
But when researchers tested beta-carotene supplements in people who smoked, two major independent studies showed supplements actually increased the risk of cancer - substantially! Beta-carotene supplements also increased the risk of heart attacks and strokes.
The chances are it's something else in carrots and tomato that protects us. It could be the effect of hundreds of these phytochemicals and antioxidants working together. But the bottom line is - think "foods first". Supplement only when there is enough evidence to convince the experts that it is worthwhile and safe to do so. The American journal of Clinical Nutrition has explored the role of functional foods in the prevention of chronic diseases such as cancer. Could foods containing significant amounts of synthetic phytochemicals provide desirable health benefits beyond basic nutrition? The study found that the vitamin C in apples with skin accounts for only 0.4 per cent of the total antioxidant activity, suggesting that most of the antioxidant activity may come from phenolics and flavonoids in apples and other fruits and vegetables.
The authors proposed that the synergistic effects of phytochemicals in fruit and vegetables are responsible for their potent antioxidant and anticancer activities, and that the benefit of a diet rich in fruit and vegetables is attributed to the complex mixture of phytochemicals present in whole foods.
There's no doubt that we will see novel nutritional approaches to reducing the risk of cancer in the future - scientists are already genetically modifying garlic to increase its selenium content. People with a family history or a genetic predisposition to cancer will be able to take supplements that are tailor-made to fight the disease. Until then, we are what we eat!