Obesity, smoking and drinking: all risk factors
The UK public is deeply sceptical about scientific claims for what causes or prevents cancer, a poll suggests.
The YouGov survey of 2,400 people for the World Cancer Research Fund (WCRF) found more than half thought scientists were always changing their minds.
More than a quarter said health advice changed constantly and the best approach was to ignore it completely.
But the WCRF said its advice, including eating more fruit and vegetables, had stayed the same for more than a decade.
The WCRF says that most scientists agree about the steps people can take to reduce their risk of cancer - and that this advice has largely stayed the same for the last 10 years.
It is thought that about a third of the most common cancers could be prevented through eating a healthy, balanced diet, being physically active and maintaining a healthy weight.
In terms of diet, scientists agree that eating plenty of fruit and vegetables and limiting intake of red and processed meat, salt and alcohol can reduce cancer risk.
Richard Evans, head of communications for WCRF, said: "It is a cause for concern if people are not listening to cancer prevention advice because they have the impression that scientists are always changing their minds.
"The fact is that WCRF and other cancer charities agree on the best ways of reducing cancer risk and this advice has stayed broadly the same for quite a long time.
"A decade ago, we were recommending that people eat a plant-based diet, be physically active and maintain a healthy weight and this is still the case today."
Mr Evans admitted there had been some changes to advice in recent years - but these were not abrupt about turns.
For instance, the evidence linking body fat with cancer has become much stronger over the last 10 years.
This has led to scientists to giving a greater emphasis to the importance of maintaining of a healthy weight, making it the second most important thing one can do to ward off cancer, after refraining from smoking.
However, Mr Evans said: "The idea that the advice from scientists changes with the wind is just not right.
"The problem is that when people hear about a single study suggesting a particular food might be good for us, it is easy to assume scientists are now telling us to start eating it.
"With the large number of new studies being published, it is perhaps not surprising that people get the impression cancer prevention advice is always changing.
"But these single studies are usually only a single piece in a jigsaw and on their own are not strong enough evidence to make conclusions.
"Often, they will be useful in giving us a lead that is worth following up with more research but should not be used to form the basis of advice."
The survey also suggested older people were most cynical about cancer prevention advice.
Jessica Harris, of the charity Cancer Research UK, said: "It's worrying if so many people think that scientists are constantly changing their minds about how to prevent cancer.
"Experts across the world agree that the best ways to reduce your risk of cancer are not smoking, keeping a healthy weight, drinking less alcohol, eating a healthy, balanced diet, being physically active and staying safe in the sun.
"These messages have not changed in recent years and are backed up by convincing evidence built up through decades of research."