Around 60 per cent of cancers are just down to 'bad luck'-and have little to do with genetics or lifestyle, researchers have claimed. Instead, they happen because of random DNA mutations that occur when stem cells divide.
Only six major cancers were more likely to be caused by environmental and dietary factors, and these include skin, throat, thyroid, lung, liver and colon cancers, say researchers from the Johns Hopkins Kimmel Cancer Centre. But even some of these could be more down to 'bad luck', such as lung cancer in the non-smoker.
However, their discoveries don't give people a licence to embrace unhealthy lifestyles, they say. A bad lifestyle can add to the 'bad luck' factor.
Nonetheless, a healthy diet will have less influence on two-thirds of cancers that are more likely to occur in tissues where there is more frequent division of stem cells in tissues. Cancer arises when tissue-specific stem cells make random mistakes, the researchers say.
They based their findings on charting the number of stem cell divisions in 31 tissue samples and compared them to the lifetime risk of cancer in those tissues.
(Source: Science, 2015; 347 (6217): 78)