The World Cancer Research Fund estimates that around 35 per cent, and possibly as many as 70 per cent, of cancers are linked to dietary factors. Learn how to reduce your risk with the right foods
The list of dietary influences on cancers is long. Diets low in fruits and vegetables are factors in many cancers, those high in salt contribute to stomach cancers and those too high in calories overall can promote hormone cancers such as breast. Smoked and burned foods, such as those cooked on barbecues, are significantly linked to many cancers. And regular alcohol intake is strongly linked to increased breast cancer risk in younger (premenopausal) women. Additionally, smoking remains one of the biggest killers as a trigger of lung cancer.
But the good news is that while some foods, and chemicals in foods, have cancer-promoting, or carcinogenic effects, many more foods have very positive effects on the initiation and progress of cancer. They have strong anti-cancer effects that have been identified in countless research papers.
So next time you go to the supermarket, make a point of adding the following foods to your basket. By eating these foods on a regular basis you can significantly reduce your statistical risk of developing a number of types of cancer.
Effective against: most cancers
Works because: the slightly bitter flavour of broccoli (and its cousins Brussels sprouts, cabbage and cauliflower) is the reason for the impressive track record these vegetables have in deterring cancer. The bitter chemicals isothiocyanates and glucosinolates actually interfere with cancer progression and deactivate harmful oestrogens associated with hormonal cancers such as breast and ovarian cancers.
Effective against: stomach, colon and most cancers
Works because: the smelly compounds in garlic are potent anti-cancer agents. All of the onion family, including leeks and shallots, contain these compounds but garlic is the most rich. Trials have shown that chemically induced cancers can be interrupted by the active compounds formed from allicin from garlic. To get the most out of garlic chop the clove and leave it to `mature' in the air for 15 minutes, and then use it in your cooking. Heating prior to this 'maturation time' by air neutralises the important compounds.
Effective against: breast, ovarian and prostate cancers
Works because: the isoflavones the soya bean contains have a gently oestrogen-mimicking effect in the human body. This helps to block the effects of more aggressive oestrogens, both natural and those from environmental chemicals from sources such as plastics and pesticides. This has the effect of limiting the risk of hormone-linked cancers in both women and men. Tofu may be more effective than other soya products or soya supplements as it has been fermented and so some potentially negative compounds are neutralised. The Japanese and Chinese who eat tofu regularly have low risks of these cancers.
Effective against: colon, prostate and breast cancers
Works because: the omega-3 fatty acids have a profound effect on cell metabolism and communication. These fatty acids also act as anti-inflammatory agents, which may be a reason for their influence on colon cancer. When the diet is higher in polyunsaturated fatty acids, such as the omega-3s, it also limits the intake and the effects of saturated fats, which are linked to increased risk of some cancers.
Effective against: most cancers
Works because: the active compound in green tea, EGCG (epigalocatechin-3-gallate) is believed to be one of the strongest antimutagenic compounds found in plants - this means it has the effect of stopping damage at a genetic level. It can also stop tumours forming their own blood supply network. Trials suggest that fairly high intakes are needed, around 10 cups a day, so replacing all hot drinks with green tea could have a beneficial effect, but only one cup a day might not. Green tea is much lower in caffeine than black tea or coffee and so is easier on sleep patterns as well.
Effective against: colon and breast cancers.
Works because: The fibre in whole grains, from cereals and wholemeal bread, are important for gut and hormonal health. The fibre gives the colon something `to work with' and also promotes good bowel bacteria. Fibre is also important in eliminating excess oestrogens. Fibre-rich cereals include bran flakes, porridge oats and muesli, though it is best to choose low-salt and low-sugar versions.
Effective against: prostate and breast cancers
Works because: the active compound in tomatoes is lycopene, one of the most potent free-radical scavengers, and seems to affect the activity of free-radicals created by tumours. Interestingly, the significant effects found against prostate and breast cancers are observed in cooked and processed tomato products, rather than raw tomatoes. This is because lycopene is made more absorbable by processing and so tomato juice, puree and canned tomatoes are most effective. It is even better to include a little olive oil when cooking with or consuming these because the oil increases absorption further.
Effective against: colon and breast cancers
Works because: the beneficial bacteria found in live yoghurt promotes gut health and improves the performance of the immune system. Regular yoghurt intake has been shown to increase levels of immune anti-cancer compounds such as interferon and natural killer cells. Because elimination of oestrogens happens in the colon, the health of the colon directly affects the development of breast cancer.
Oranges and carrots
Effective against: lung cancer particularly, and most cancers in general Works because: they are rich, respectively, in vitamin C and beta-carotene. All fruits and vegetables are rich in antioxidants and many are rich in these two compounds. These water-soluble antioxidants are important at protecting lung tissue, which is a very water-rich environment. High blood levels of these antioxidants are linked to much-reduced levels of lung, and other, cancers. However taking beta-carotene in supplement form may be ill-advised for smokers as trials have shown higher mortality levels, probably as smokers' lungs already have advanced damage. A diet high in fruits and vegetables is highly protective against lung cancer and even in countries where smoking is more prevalent, such as Greece and Spain, fruits and vegetables seem to be protective.
Linseeds (also called flax seeds)
Effective against: breast and colon cancers
Works because: the lignans they contain are gelatinous fibres which are highly protective against hormonal cancers. They convert in the bowel, in the presence of beneficial bacteria (see yoghurt above) to even more potent compounds which block the effects of oestrogen. Additionally, like all fibres, they have a positive effect on bowel health - indeed one of the most effective remedies against constipation is to take one or two teaspoons of linseeds pre-soaked for 30 minutes in water or fruit juice. They are also particularly rich in omega-3 fatty acids.
Suzannah Olivier is a nutritionist and the author of many books including The Breast Cancer Prevention and Recovery Diet (Penguin £9.99). Her latest book is Food Medicine (Robinson £9.99) Visit Suzannah's website www.healthandnutrition.co.uk
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