Does organic food reduce cancer risk?
Published: 21 Apr 2014
A widely publicised study has suggested that eating organic food doesn't stop you getting cancer. Pat Thomas finds the study deeply unconvincing - and wonders why Cancer Research UK is so quick to trumpet its conclusions.
Both sides of the debate are scrambling to make their soundbites seem more sensible than the other guys' - and for reasons known only to newspaper photo editors, pictures of Gwyneth Paltrow are being used to illustrate the 'typical' organic eater.
Get ready folks, the circus has come to town.
In slightly more than a soundbite here is my take.
The study, by scientists from Oxford University, used data from a larger study called the Million Women Study. Around 623,000 women aged 50 or over were asked via questionnaire whether they ate organic foods. These women were then followed over a 9-year period to see who developed any of the most common types of cancer.
The researchers say they found no difference in overall cancer risk between those who never ate organic and those who usually or always did.
Several things occur to me ...
Very few women in the study actually ate a fully organic diet. Indeed at the beginning of the study the scientists determined that 30% (180,000), 63% (224,000) and 7% (45,000) fell into never, sometimes, or usually / always eating organic food categories, respectively.
Thus the number of women who ate organic food was very small and food questionnaires are a notoriously inaccurate way of understanding how people eat.
A 2010 report by commissioned by the charity Cancer Research UK, which also commissioned this study, estimated that 43% of new cancers were due to largely preventable dietary and lifestyle factors. That means that 60% of cancers are due to something else.
Even if you were to accept that the genetic contribution to cancer was as high as 20% (I don't) that still means that 40% of cancers are caused by something else, which diet alone is unlikely to address.
Nutritional composition matters too
The nutritional composition of the women's diets is as important as whether they were organic or not. It would be interesting to know how the researchers defined organic food - was it fresh or processed?
A diet of organic doughnuts, crisps and sodas is unlikely to be protective (though that's a fight for another day).
Cancer is a slow developing disease. This makes it very difficult to study its causes. The nine years of the study is probably not long enough to show any significant differences between groups, especially for some of the cancers studied, some of which, in the grand scheme of things, are still relatively rare.
Early shorter-term studies of mammographies, for example, were once used to suggest that they reduced the risk of death from breast cancer. But a 25-year study published this year has shown this was not the case.
The researchers say that an organic diet did not prevent cancer, but in this study it was associated with a 21% decrease in the risk of non-Hodgkin lymphoma - which should probably not be dismissed as "chance", as has been done.
Why put the study behind a paywall?
If the researchers are so sure of their findings why didn't they make them 'open access' so that everyone could read - and immediately, intelligently comment on them? The reason, I would suggest, is that they want to make headlines on their basically crappy (that's the scientific term) study, before anyone can tear it apart.
No single dietary intervention can protect you from disease or early death. This includes vegetarianism which has been shown to reduce, but not prevent, the incidence of and early death from a whole range of diseases including cerebrovascular disease and various cancers.
Eating organic, apart from its multitude of other health and environmental benefits, still remains one of the best ways to avoid pesticide residues in your food (levels of which are rising).
Avoiding pesticide residues is a sensible health precaution because the link between pesticide exposure and cancer is well established.
CRUK - not impressed by organic food
Depressing, then, to read Dr Claire Knight, from Cancer Research UK, quip that: "This study adds to the evidence that eating organically grown food doesn't lower your overall cancer risk. But if you're anxious about pesticide residues on fruit and vegetables, it's a good idea to wash them before eating."
Pesticides are present in many foods and most can't be simply 'washed away' - otherwise they would not work in the fields. They stay on plants and in our bodies for a long time.
What is more you can't wash foods such as flour, cereals and bread. As our friends at the Soil Association replied: "we'd be interested to know how she expects consumers to wash loaves of bread."
The Million Women Study has generated a lot of data including such gems as whether having a cat gives you cancer, whether taking a nap means you have cancer and whether having babies and breastfeeding makes you fat which will probably give you cancer.
I'm only partly joking. These are real studies. The point is, dismissing organic food in the same soundbite way is shallow, ridiculous and may even, in the long-term, prove terribly misleading.
Courtesy of The Ecologist