In the most comprehensive study ever to be carried out into the nutritional content of organic food compared to ordinary fare, scientists found no significant difference in vitamins and minerals.

A separate study found there are no extra health benefits to eating organic food rather than meat, fruits or vegetables grown on intensive farms.

The Food Standards Agency (FSA), which commissioned the research by the London School of Hygiene and Tropical Medicine, concluded there was no reason to buy expensive organic food for nutritional reasons.

The study is likely to come as a blow to the billion-pound industry which is already struggling in the economic downturn as shoppers turn away from more expensive goods. For example, an organic chicken costs three times the price of a more conventionally-reared bird.

But celebrity chefs and organic farmers said the studies failed to take into account the health impact of the "cocktail of chemicals" left on conventional food and the environmental benefits of growing organic food on wildlife-friendly farms. Advocates claim the produce is better for you, with some claiming it can help cure skin conditions, asthma and even cancers.

However previous studies have proved confusing, with some claiming organic foods can provide more vitamins, while others find no difference to ordinary foods.

The new research looked for the first time at the best evidence over the last 50 years. After looking at 160 studies on the nutritional content of organic foods versus non organic it concluded there was no significant difference in vitamins and minerals that are important to human health. A further study of more than 50 studies on the health implications found no good evidence that organic food is better for you than non-organic.

Dr Alan Dangour, of the LSHTM, who carried out the studies, said the report was the most comprehensive review of the health benefits of organic food ever carried out.

"Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority," he said.

Gill Fine, FSA Director of Consumer Choice and Dietary Health, said there is no need for people to buy highly-priced organic food for the health benefits.

"The study does not mean that people should not eat organic food. What it shows is there is little, if any, nutritional difference between organic and conventionally produced food and that there is no evidence of additional health benefits from eating organic food."

The study did not look at pesticide residue or the environmental implications of organic food because this would be beyond the specialism of the scientists involved.

Lord Melchett, Policy Director of The Soil Association, argued that the small differences in minerals and vitamins found in the study do benefit health.

"The FSA study does show generally that there are beneficial nutrients in organic than non-organic, but the researchers have concluded these are not important - for example, flavonoids and beta carotene. We think they are and more recent studies back these up. "

Anthony Worrall Thompson, the celebrity chef, said an organic diet has made him healthier over the past 14 years, and the study failed to look at the health benefits of no pesticide residue and the environmental benefits of organic farms.

"There probably are as many nutrients in non-organic food as organic but there are a lot of other things going on – no one has done a study on the cocktail of chemicals on non-organic food."