UK researchers claim there is evidence that some food components including fibre, folate, polyunsaturated fatty acids, plant chemicals such as glucosinolates or flavonoids and gut fermentation products such as butyrate, can provide protection at various stages of cancer formation.
"The adverse effects of diet are caused by over-consumption of energy coupled with inadequate intakes of protective substances, such as micronutrients, dietary fibre and a variety of plant chemicals," said Professor Ian Johnson, author of the review - 'New approaches to the role of diet in the prevention of cancers of the alimentary tract', published in Mutation Research focusing on Nutrition and Carcinogenesis - and head of Gastrointestinal Health and Function at the Norwich-based Institute of Food Research.
Fibre ingredients on the market today range from prebiotic inulins supplied by European firms such as Sensus, Orafti and Cosucra, to traditional food ingredients such as guar gum as well as and resistant starches like the identity-preserved starch Hi-maize from National Starch.
Consumer interest in health-providing food products is currently driving the market for fibre ingredients as food formulators turn to new product recipes with a health promoting feature.
Leading cereal brand Kellogg's, for example, has added inulin to a new brand called Muddles, which claims in its supporting literature that a 30g serving of the cereal provides 2g of inulin, more than a third of the required 5g of inulin each day that can help to optimise digestive health.
Market analysts Frost & Sullivan claim that product launches like this are driving sales of inulin, in a European prebiotics market, currently worth €87 million and set to reach €179.7 million by 2010.
"Colorectal cancer is clearly a disease of affluence and about 80 per cent of cases are attributable in some way to diet. Many of the mechanisms have yet to be discovered, but basically what this means is that people can help to protect themselves by controlling their weight and by eating diets rich in fruits and vegetables and other sources of fibre," added Professor Johnson.
Of the 10 million new cases of cancer diagnosed in 2000 in the UK, around 2.3 million were cancers of the digestive organs - pharynx, oesophagus, stomach or colorectum.
The walls of the gut are lined with a layer of cells, the epithelium, covered with a film of mucus. The epithelium is the first contact for food, bacteria and anything else ingested. It is the body's first line of internal defence, but can also be susceptible to the development of abnormalities over time. The epithelium is normally renewed by rapidly dividing stem cells, which can also give rise to new growths called polyps. These usually remain benign, but some may acquire so many genetic abnormalities that they eventually form a cancerous tumour.
Looking into the role food components could play in averting the onset of cancer, further research published in the same journal as Professor Johnson's review (Mutation Research 2004 Jul 13;551(1-2):245-54) suggests that enzymes called COX-2 that enable genetically abnormal cells to survive were suppressed by the flavonoid quercetin.
Compounds can also increase the activity of detoxifying enzymes, and components in the diet have been shown to act synergistically in this way - so that they are even more effective when combined. These enzymes delete genetically damaged epithelial cells, writes a paper to be published in September that demonstrates a synergy between sulforaphane, a plant chemical in brassica vegetables, and apigenin (a flavonoid). (Interactions between sulforaphane and apigenin in the induction of UGT1A1 and GSTA1 in CaCo-2 cells, Carcinogenesis, Vol. 25, Issue 9 September 2004.)