From The Guardian:

“The research was peer-reviewed and is published in a respected scientific journal, the British Journal of Nutrition.

The results are based on an analysis of 343 peer-reviewed studies from around the world – more than ever before – which examine differences between organic and conventional fruit, vegetables and cereals.

“The crucially important thing about this research is that it shatters the myth that how we farm does not affect the quality of the food we eat,” said Helen Browning, chief executive of Soil Association, which campaigns for organic farming.

UK sales of organic food, which is often considerably more expensive than non-organic, are recovering after a slump during the economic crisis.

Plants produce many of their antioxidant compounds to fight back against pest attacks, so the higher levels in organic crops may result from their lack of protection by chemical sprays. But the scientists say other reasons may be important, such as organic varieties being bred for toughness and not being overfed with artificial fertilisers.

Leifert and his colleagues conclude that many antioxidants “have previously been linked to a reduced risk of chronic diseases, including cardiovascular diseases, neurodegenerative diseases and certain cancers”. But they also note that no long-term studies showing health benefits from a broad organic diet have yet been conducted.

The researchers found much higher levels of cadmium, a toxic metal, in conventional crops. Pesticide residues were found on conventional crops four times more often than on organic food. The research was funded by the EU and an organic farming charity.

The research is certain to be criticised: the inclusion of so many studies in the analysis could mean poor quality work skews the results, although the team did “sensitivity analyses” and found that excluding weaker work did not significantly change the outcome.”

link to report at Cambridge Journals

http://www.theguardian.com/environment/2014/jul/11/organic-food-more-antioxidants-study