Confirming findings of a recent study by Japanese researchers, the WHO's cancer research agency also reported recently on the strong evidence that eating fruits and vegetables could lower the risk of cancer, particularly cancers of the gastrointestinal tract.
The International Agency of Research on Cancer (IARC) carried out a full review of current knowledge and research on the link between dietary intake of fruit and vegetables and cancer.
The group of 22 scientists (from 10 countries) concluded that findings from both human studies and animal experimental studies "indicate that a higher intake of fruits and vegetables is associated with a lower risk of various types of cancer."
The clearest evidence of a cancer-protective effect from eating more fruits is for stomach, lung and oesophageal cancers. Similarly, "a higher intake of vegetables probably reduces the incidence of cancers of the oesophagus and colon-rectum," reported the team at a week-long meeting in Lyon, France.
"In many studies, there is a fairly consistent association of higher levels of fruits and vegetables intake with some reduction in cancer risk," said Professor Paul Kleihues, director of the IARC. "This, plus the evidence of beneficial effects of fruits and vegetables on other major diseases such as heart disease, indicates that individuals and communities should increase their intake of these foods." He said the findings were important for governments, the food industry and consumers.
The working group estimated that approximately one in ten cancers in western populations are due to an insufficient intake of fruits and vegetables. Similar, although variable, fractions apply to other populations around the world, and may be higher in regions where the intake of fruits and vegetables is lower.
The group's chairman, Professor Tony McMichael, from the Australian National University, pointed out that the evidence for any particular type of cancer in relation to fruits and vegetables intake lacks certainty. However, the pattern of findings for cancers overall is persuasive, he said.
"Individual dietary habits are complex," said Professor McMichael, "and they are accompanied by various other personal behaviours, such as smoking and alcohol consumption, that can also affect cancer risk. So, it is not easy to get conclusive evidence on diet-cancer relationships."
However, long-term follow-up studies involving large numbers from the general population are now providing higher-quality information about these relationships, he said.