By Clare Murphy
Health reporter, BBC News
Eating more fruit and vegetables has only a modest effect on protecting against
cancer, a study into the link between diet and disease has found.
The study of 500,000 Europeans joins a growing body of evidence undermining the
high hopes that pushing "five-a-day" might slash Western cancer rates.
The international team of researchers estimates only around 2.5% of cancers
could be averted by increasing intake.
But experts stress eating fruit and vegetables is still key to good health.
In 1990, the World Health Organization recommended that everyone consume at
least five portions of fruit and vegetables a day to prevent cancer and other
chronic diseases.
The advice has formed a central plank of public health campaigns in many
developed countries. It has been promoted in the UK since 2003 and in the US
for nearly two decades.
But research has failed to substantiate the suggestion that as many as 50% of
cancers could be prevented by boosting the public's consumption of fruit and
vegetables.
It's still a good idea to eat your five-a-day but remember that fruits and
vegetables are pieces in a much larger lifestyle jigsaw
Yinka Ebo Cancer Research UK
This latest study, which analysed recruits from 10 countries to the
highly-regarded European Prospective Investigation into Cancer and Nutrition,
confirms that the association between fruit and vegetable intake and reduced
cancer risk is indeed weak.
The team, led by researchers from the Mount Sinai School of Medicine, in New
York, took into account lifestyle factors such as smoking and exercise when
drawing their conclusions.
But writing in the Journal of the National Cancer Institute, they said they
could not rule out that even the small reduction in cancer risk seen was down
to the fact that the kind of people who ate more fruit and vegetables lived
healthier lives in many other respects too.
Broccoli not biscuits
In the best case scenario, an extra two portions of fruit and vegetables each
day could prevent 2.6% of cancers in men and 2.3% of cases in women, the study
concluded.
Research should focus more sharply on specific fruits and vegetables and
their constitutents
Walter Willett Harvard School of Public Health
Vegetables, which tend to be richer in nutrients, appeared to be more
beneficial than fruits, while heavy drinkers seemed to gain the most from a
higher intake of both when it came to protection from cancers caused by alcohol
and smoking.
In an accompanying editorial, Professor Walter Willet of Harvard University
said the research strongly confirmed the findings of other studies, showing
"that any association of intake and fruits and vegetables with risk of cancer
is weak at best".
But he stressed specific substances contained in certain fruit and vegetables,
if harnessed, could still have an important, protective effect.
Substantial evidence suggests lycopene from tomatoes, for instance, may reduce
the risk of prostate cancer, while chemicals in broccoli are thought to
stimulate a gene which protects against bowel cancer.
And data still suggests fruit and vegetables may provide protection against
cardiovascular disease, one of the major killers in the developed world -
although this too has yet to be proven categorically.
Keeping lean
But while the links between diet and cancer remain unclear, obesity is now seen
as an established risk factor.
Fruit and vegetables could therefore be beneficial just by virtue of taking the
place of more calorific fare, health experts say.
In any event, a reduced risk of 2.5% should not be dismissed out of hand, the
World Cancer Research Fund argues.
"For the UK, this works out as about 7,000 cases a year, which is a significant
number," says Dr Rachel Thompson from the charity, which in a major 1997 report
said there was "convincing evidence" of the protective effect of fruit and
vegetables.
Yinka Ebo of Cancer Research UK said: "It's still a good idea to eat your
five-a-day but remember that fruits and vegetables are pieces in a much larger
lifestyle jigsaw.
"There are many things we can do to lower our chances of developing cancer such
as not smoking, keeping a healthy weight, cutting down on alcohol, eating a
healthy balanced diet, being physically active and staying safe in the sun."
Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/8605270.stm
Published: 2010/04/07 00:31:56 GMT