The report, commissioned by Cancer Research UK, launches the charity's new landmark campaign “ Reduce The Risk “ which aims to help people learn how lifestyle changes can drastically alter their odds of being diagnosed with cancer.

Scientific research has shown that at least half of all cases of cancer could be prevented. But this message needs to reach the public.

The results of the survey reveal there is confusion over what increases the risk of cancer.

Of the 4,000 people questioned two thirds (66 per cent) were unaware that being overweight or obese increases the risk of some cancers. And almost exactly the same number (67 per cent) did not know that a diet low in fruit and vegetables could increase their chance of getting the disease.

Only one third (34 per cent) mentioned drinking less alcohol as a way of reducing risk. And around 75 per cent of those questioned were ignorant of the cancer risks posed by taking HRT or having many sexual partners.

But almost a quarter (24 per cent) believed living near power lines was a risk. And more than one third (34 per cent) thought stress was linked to cancer. Yet there is no strong scientific evidence to support either of these beliefs.

These findings are part of a comprehensive survey of 4,000 people designed to assess how much they know about cancer which is diagnosed in more than 270,000 people in Britain each year.

But there is some good news. The message that 'smoking kills' has got through to most people. More than 90 per cent of those questioned said smoking increased your chance of developing cancer. This rose to 94 per cent in the 45-54 age bracket.

And it was encouraging that the vast majority of people knew that sunburn increases skin cancer risk.

Launching the Reduce the Risk campaign Cancer Research UK's Chief Executive Professor Alex Markham says: "The fundamental aim of this campaign is to alert everyone to the fact that each one of us can reduce our risk of getting cancer. We estimate that half of cancer cases could be prevented. There is no magic pill to prevent us getting the disease but there are many things we can all do in our daily lives to improve our chances of avoiding it.

"Already we are making headway on tobacco. The vast majority of people in this country know that smoking causes cancer. And the vast majority of smokers want to give up. This is heartening news.

"But our survey has shown there is a great deal more to do. Lack of awareness among the public is a major concern. It is important for people to realise that being a healthy weight and eating a properly balanced diet with plenty of fruit and vegetables can really make a difference to their cancer risk. As can maintaining an active lifestyle and taking advantage of screening programmes."

Television presenter Gaby Roslin, who is helping to launch Reduce the Risk, says: "The Reduce the Risk campaign strikes a very personal chord with me. Nine years ago my father was diagnosed with bowel cancer but he is now doing very well. Sadly, my mother died from lung cancer almost eight years ago.

"Because of what happened in my family I have tried hard to improve my lifestyle and have a much better diet now than when I was younger. I drink plenty of water and eat loads of fresh fruit and veg and fresh fish. The truth is I feel a lot better and I have lost weight too so the bonuses of changing your lifestyle are about now as well as the future."

Film and TV actor Martin Clunes is also backing the charity's campaign. He says: "I think Cancer Research UK has come up with a terrific campaign for anyone who wants to find out how they really can cut their chances of getting cancer. Reduce the Risk will make people like me “ who are in their 40s “ start to think about their health seriously perhaps for the first time. And as a parent you do start worrying a lot more about staying healthy for the future because you have that extra responsibility."

The five-year Reduce the Risk campaign will target thousands of GPs' surgeries, health promotion units, hospitals and outpatient departments with leaflets and posters on its key messages. Information will be distributed to local authority leisure centres, swimming pools and shopping centres. The charity will produce guidance leaflets on healthy eating and distribute Reduce the Risk messages to almost half a million participants in Cancer Research UK's Race for Life fundraising event this summer.

Half of all cancers could be prevented by changes to lifestyle so Reduce the Risk invites people to take action in five key areas:

Stop smoking

This is the best present you will ever give yourself. We know it's hard but support and effective treatments are available to help you quit smoking or chewing tobacco. Give up now and greatly reduce your risk of cancer.

Stay in shape

Cut your cancer risk by keeping a healthy weight. Being overweight or obese increases your risk of several cancers. Try to balance the energy you take in from food with the energy you burn through activity. Just 30 minutes five days a week of moderate exercise such as brisk walking, gardening or swimming will keep you healthy.

Eat and drink healthily

Limit alcohol and maintain a healthy diet to reduce your risk. Alcohol increases your risk of certain cancers, more so if you also smoke. Try to limit the amount you drink. Aim for a healthy balanced diet, including plenty of fruit and vegetables “ at least five portions a day.

Be SunSmart

Protect yourself from the sun and harmful UV. Cover up and take care not to burn. Watch moles for any changes and get unusual skin blemishes checked out by the doctor. Avoid using sunbeds.

Look after number one

Know your body, be aware of any changes and contact your doctor if you notice anything unusual. Go for screening when invited “ it could save your life. For more information about the campaign visit: www.reducetherisk.

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