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Claire Turnbull: Food and Cancer - 23 August

Food and cancer - cut your risk!

1. So is it really true we can cut our cancer risk by changing the way we eat?

We all know there's no one magic food or action that will prevent cancer, but certainly there are things you can do to reduce your risk. I have 10 things to tell you about today!

2. So, canned tomatoes, how are they magic?

Tomatoes get their red colour from a carotenoid called lycopene. According to the World Cancer Research Fund and American Institute for Cancer Research report in 2007 which considered all the studies conducted up to that time, lycopene probably reduces the risk of prostate cancer. Lycopene from tomatoes is more available and better absorbed by our body when they are cooked, crushed or eaten with fat such as olive oil.

Add a can of tomatoes or a generous spoonful of tomato paste to soups and casseroles.

3. And brazil nuts?

Brazil nuts are high in the mineral selenium. Eating just two Brazil nuts a day is as effective at increasing blood selenium levels as taking a supplement of 100 micrograms.

Selenium is a powerful antioxidant which has been associated with less skin cancer and probably protects against prostate cancer according to the World Cancer Research Fund.

Because New Zealand's soil is deficient in selenium we are more likely to have lower blood levels of this mineral. So snacking on one or two Brazil nuts a day is a simple way to keep these levels up. Selenium is toxic in high doses so don't be tempted to think that if a little is good, more must be better.

Snack on one or two Brazil nuts a day.

3. What about ham? Can you still eat that?

Meats that are smoked or cured with nitrates such as ham, bacon, salami and sausages have been linked to colorectal cancer. People with the highest intake of cured meats had a 20% greater risk of colorectal cancer compared with those with the lowest intake.

Swap your ham sandwich for roast meat, pork or chicken. Choose vegetarian or chicken pizza rather than meat-lovers.

4. Garlic?

When we chop garlic it allows an enzyme present in garlic cells called allinase to start a reaction that produces anti-cancer chemicals called allyl sulphides. If you leave it for 10-15 minutes after chopping, the anti-cancer compounds will be retained during cooking. If you cook it too soon, the enzyme won't have had time to produce those compounds.

In animal studies and laboratory tests, the allyl sulphides found in garlic inhibit colon tumour formation. Garlic also has antibiotic properties which are thought to help protect against stomach cancer. The World Cancer Research Fund states that garlic probably protects against colorectal and stomach cancer.

Peel or chop garlic 10-15 minutes before cooking.

5. How can smoothies help?

Calcium, in particular milk, probably protects against colorectal cancer and may reduce the risk of breast cancer. Dairy products, calcium and the risk of breast cancer. It's thought that calcium works by enhancing DNA's ability to repair itself. If this repair mechanism is disrupted it may lead to cancer.

Berries are rich in cancer fighting anthocyanins. Anthocyanins inhibit cancer growth and stimulate cancer cells to self destruct.
If you are a bloke, don't go overboard on the calcium: large amounts may increase the risk of prostate cancer. Researchers studied around 27,000 men from the Singapore Chinese Health Study and found the higher their calcium intake the greater the risk of prostate cancer. What made this interesting was that most of the calcium came from non-dairy foods.

Low-fat berry smoothie are great!

6. Can exercise help!

Sure - get out for a walk!

There is convincing evidence that physical activity reduces the risk of colorectal cancer and probably reduces the risk of endometrial cancer and in post-menopausal women, the risk of breast cancer. A survey of 15,000 women found that exercise had a protective effect against breast cancer throughout their life provided they didn't have a family history. One way exercise is thought to reduce risk is by reducing estrogen levels. Lower estrogen levels are thought to be protective against breast cancer.

7. Can cabbage help?

Cruciferous vegetables such as cabbage, broccoli, cauliflower and bok choy contain cancer fighting isothiocyanates which may reduce the risk of bladder, lung and breast cancer. Just three or more servings a month of raw cruciferous vegetables may reduce bladder cancer risk by about 40%. Make sure the vegetables are raw or lightly cooked such as in stir-frying. Cooking can destroy 60-90% of the anti-cancer compounds.

Make coleslaw with raw cabbage. Stir-fry some cauliflower, broccoli or bok choy.

8. Greens are good for us - why is spinach for good?

Dark green leafy vegetables such as spinach and silverbeet are rich in carotenoids and folate. Carotenoids reduce the risk of cancer of the mouth, pharynx, larynx, lung and oesophagus.

Folate is essential for normal DNA functioning. It also helps make and repair DNA. Folate probably protects against pancreatic cancer.

Add two chunks of frozen spinach to your bolognaise mixture.

9. Tea, how does that help?

The polyphenols in tea act as strong antioxidants. Green tea has an especially active anti-cancer agent called EGCG. One study found that leaving the tea to infuse for five minutes released more than 80% of the effective catechins. These substances are associated with a reduced risk of cancer of the breast, pancreas, colon, esophagous and lung. It may also slow the growth of prostate cancer. (Clinical Cancer Research march 1 issue 2007 Green tea and Cox-1 inhibitors combine to slow growth of prostate cancer)

Some researchers have suggested that we need to drink seven or eight cups a day to absorb enough of the effective substances to make a difference. So boil the jug and make yourself another cup of green tea right now!

Leave the tea bag in your green tea for 5 minutes

10. No more barbecue meat?

Cooking meat at high temperatures increases the amount of heterocyclic amines. HCA's form when amino acids (from protein) and creatine (a chemical found in muscles) react at high cooking temperatures. Seventeen different HCA's have been found in cooked meat that may increase the risk of cancer. One study found that three times more HCA's were found in meat cooked at 250C compared to meat cooked at 200C.

A roast has less nasty HCA's than a well cooked steak but not if it's served with gravy made from the meat drippings. All those burnt bits stuck at the bottom of the pan may taste good but are not so good for your risk of cancer. Serve your roast meat with mustard, mint sauce or apple sauce.

Swap the barbecue or fried meat for roast or casserole.