EATING pesticide-free organic food does nothing to reduce a woman's risk of cancer, a study has found.
Researchers asked 600,000 women aged 50 or over whether they ate organic food and monitored their health for nine years.
In total, around 50,000 of the women developed one of 16 of the most common cancers during the period of the study.
But a comparison between 180 women who never ate organic food and 45,000 who "usually" or "always" chose organic found no difference in overall cancer risk.
In fact, a small increased risk of breast cancer was seen in organic consumers.
But this result could be due to other factors or pure chance, the scientists said.
A reduction in the risk of the blood cancer non-Hodgkin lymphoma was also linked to eating organic.
However, again scientists said this may not be a genuine association.
Professor Tim Key, a Cancer Research UK-funded scientist at Oxford University, said: "In this large study of middle-aged women in the UK we found no evidence that a woman's overall cancer risk was decreased if she generally ate organic food.
"More research is needed to follow-up our findings of a possible reduction in risk for non-Hodgkin lymphoma."
There are concerns that widely used pesticides might increase cancer risk, but so far the evidence has been inconclusive. Conventionally grown fruit and vegetables contain very small pesticide residues.
The new findings appear in the British Journal of Cancer, which is owned by Cancer Research UK.
Dr Claire Knight, the charity's health information manager, said: "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.
"Scientists have estimated that over 9pc of cancer cases in the UK may be linked to dietary factors, of which almost 5pc are linked to not eating enough fruit and vegetables."