Study sparks organic foods debate
A new scientific review claims organic foods are higher in nutrients and lower in pesticides compared with conventionally grown varieties.
Its authors carried out an analysis of 343 peer-reviewed studies looking at the composition of crops and foods.
They concluded organic crops had higher levels of certain antioxidants, such as polyphenols, which have been linked to health benefits.
But critics of the review said its claims had been overstated.
They argued the differences found between organic and non-organic crops were not significant, and that public health would be best served by getting people to eat more fruit and veg, irrespective of the farming methods used in the crops' production.
The latest study runs counter to two previous systematic reviews which found that organic and non-organic foods were broadly comparable in nutritional terms.
'Five a day'
The new review, published in the British Journal of Nutrition, was funded by the EU and the Sheepdrove Trust, an organic farming charity.
Its international team of scientists reviewed the available literature comparing the chemical content of foods - primarily cereals, vegetables and fruit - and crop-based products, such as seed oils, wine and baby food.
The meta-analysis found differences between organic and non-organic varieties which the team concluded were "significant and meaningful".
Organic foods had elevated levels of compounds often described as "antioxidants" - such as phenolic acids, flavonols and anthocyanins.
"Many of these compounds have previously been linked to a reduced risk of chronic diseases, including cardiovascular disease and neurodegenerative diseases and certain cancers," the authors wrote.
However, levels of proteins, amino acids and nitrogen were lower in the organic crops sampled.
Lead author Prof Carlo Leifert of Newcastle University said: "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".
However, the study noted, "it is important to point out that there is still a lack of knowledge about the potential human health impacts of increasing antioxidant intake levels and switching to organic food consumption."
The new findings stand opposed to two previous meta-analyses that found no significant composition differences between organic and conventionally farmed crops.
In 2012, a study by Stanford University scientists looked at 237 papers and concluded that: "No consistent differences were seen in the vitamin content of organic products, and only one nutrient - phosphorus - was significantly higher in organic versus conventionally grown produce."
In 2009, a Food Standards Agency report led by Dr Alan Dangour analysed 55 studies and found organic and non-organic foods were "broadly comparable" in their nutrient content.
There was no difference in the majority of nutrients analysed, and "no good evidence that increased dietary intake of the nutrients identified to be present in larger amounts in [organic crops] and livestock products would be of benefit to individuals."
Prof Leifert said: "The main difference between the two studies is time. Research in this area has been slow to take off the ground, and we have far more data available to us now than five years ago."
However, his conclusions were questioned by two nutritional science experts independent of the research group.
Prof Tom Sanders, head of the Diabetes and Nutritional Sciences Division at King's College London's School of Medicine, said: "This article is misleading because it refers to antioxidants in plants as if they were a class of essential nutrients, which they are not.
"In terms of macronutrients (protein, carbohydrate, fat), the organic products contained less protein. Other nutrient differences were trivial and well inside the normal range of variation that occurs with different varieties, soil types and variations in weather.
"This study provides no evidence to change my views that there are no meaningful nutritional differences between conventional produced and organic crops."
Prof Richard Mithen, leader of the Food and Health Programme at the Institute of Food Research, added: "There is no evidence provided that the relatively modest differences in the levels of some of these compounds would have any consequences (good or bad) on public health.
"The references to 'antioxidants' and 'antioxidant activity', and various 'antioxidant' assays would suggest a poor knowledge of the current understanding within the nutrition community of how fruit and vegetables may maintain and improve health."
Dr Alison Tedstone, chief nutritionist at Public Health England, said: "PHE welcome this addition to the evidence base but we cannot assess the potential impact of organic foods on public health from this study alone.
"Ultimately, we all need to eat more fruit and vegetables regardless of whether they are organic or not to form part of a healthy balanced diet, which will help protect health."