A new scientific study claims organic foods contain up to 69% more key antioxidants than conventionally grown crops.

Researchers at Newcastle University recruited a team of international experts to 343 studies into the compositional differences between organic and conventional crops.

And the team found that a switch to eating organic fruit, vegetables and cereals – and food made from them – would provide additional antioxidants equivalent to eating between one to two extra portions of fruit a day.

The study, started under the European Sixth Framework Programme project QualityLowInputFood and completed later with funding from the Sheepdrove Trust, found that concentrations of antioxidants such as polyphenolics were between 18-69% higher in organically grown crops.

Numerous studies have linked antioxidants to a reduced risk of chronic diseases, including cardiovascular and neurodegenerative diseases and certain cancers.

The study also found significantly lower levels of toxic heavy metals in organic crops (up to 50% less).

Nitrogen concentrations were found to be significantly lower in organic crops. Concentrations of total nitrogen were 10%, nitrate 30% and nitrite 87% lower in organic compared with conventional crops.

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The study also found that pesticide residues were four times more likely to be found in conventional crops than organic ones.

But critics of the study have pointed out that organic foods are more expensive than non-organic foods and consumers should instead focus on eating more fruit and vegetables to maintain a healthy, balanced diet.

“This study demonstrates that choosing food produced according to organic standards can lead to increased intake of nutritionally desirable antioxidants and reduced exposure to toxic heavy metals,” said Newcastle University’s professor Carlo Leifert and study lead.

“This constitutes an important addition to the information currently available to consumers which until now has been confusing and in many cases is conflicting.”

Researchers said the study was the “most extensive analysis of the nutrient content in organic versus conventionally produced foods ever undertaken”.

However, the findings contradict those of a 2009 Food Standards Agency (FSA) commissioned study, which found there were no substantial differences or significant nutritional benefits from organic food.

The FSA commissioned study based its conclusions on only 46 publications covering crops, meat and dairy, while Newcastle led meta-analysis is based on data from 343 peer-reviewed publications on composition difference between organic and conventional crops now available.

Professor Leifert added: “The organic v non-organic debate has rumbled on for decades now but the evidence from this study is overwhelming – that organic food is high in antioxidants and lower in toxic metals and pesticides.”

The Soil Association said the study “shattered the myth” that how we farm “does not affect the quality of the food we eat”.

Its chief executive, Helen Browning, said: “We know that people choose organic food because they believe it is better for them, as well as for wildlife, animal welfare and the environment, and this research backs up what people think about organic food.

“In other countries there has long been much higher levels of support and acceptance of the benefits of organic food and farming. We hope these findings will bring the UK in line with the rest of Europe, when it comes to both attitudes to organic food and support for organic farming.”

But the Crop Protection Association (CPA) said the study pointed to “slightly higher levels of antioxidants” in organic foods and the differences in pesticide levels between organic and conventional foods were “relatively small”.

CPA chief executive Nick von Westenholz said: “What is important is that people have a healthy, well-balanced diet which is high in fruit and vegetables, whether conventionally grown or otherwise.

“In regards to pesticide residues, year on year, results show that no consumers are exposed to residues at levels that threaten their health. Regulators have repeatedly confirmed that low levels of residues in food are safe for consumers.”