The research, led by Newcastle University and published last week in the British Journal of Nutrition, found concentrations of antioxidants such as polyphenolics that were 18 to 69 percent higher in organic food.
“Many of these compounds have previously been linked to a reduced risk of chronic diseases, including CVD and neurodegenerative diseases and certain cancers, in dietary intervention and epidemiological studies,” the study reads.
The researchers suggest that switching to eating organic fruit, vegetable and cereals provide consumers 20 to 40 percent more antioxidants, which would be equivalent to eating between one or two extra servings of fruit and vegetables a day.
The team also found that pesticide residues were four times more likely to be found in conventional crops than organic ones and that levels of the toxic heavy metal cadmium are nearly twice as high for conventionally-grown foods.
However, the U.S. Department of Agriculture’s Pesticide Data Program (PDP) tests conventional fruits and vegetables each year and finds that “U.S. food does not pose a safety concern based upon pesticide residues.” As for cadmium, the study itself notes that “the exact health beneﬁts associated with reducing [cadmium] intake levels via a switch to organic food consumption are difﬁcult to estimate.”
The paper is a meta-analysis of more than 340 studies of the compositional differences between organic and conventional crops.
“There are a lot more high-quality studies comparing the nutritional quality and safety of organic verses conventional foods and this larger, higher-quality database supports some conclusions that were not reached in some of the earlier studies,” said one of the authors, Professor Charles Benbrook of Washington State University.
While less pesticides on organic foods may not have come as a big surprise, but Benbrook said the cadmium findings were certainly interesting. “None of the earlier reviews picked that up and reported significant differences in cadmium levels, but our meta-analysis was much more sophisticated,” he said. It takes into account the sample size and variance of each study included in the analysis, in addition to the mean level of nutrients.
The findings contradict a 2009 study commissioned by the UK Food Standards Agency which found there were no substantial differences or significant nutritional benefits from organic food.
Critics of this latest study suggest that it overstates the public health significance of the findings. While the increased antioxidants may be news, nutritionists have a hard time saying exactly how beneficial they are.
“This article is misleading because it refers to antioxidants in plants as if they were a class of essential nutrients, which they are not. The article misleadingly suggest health benefits result from a high consumption of antioxidants, particularly cancer protection,” Professor Tom Sanders of King’s College London’s School of Medicine told The Independent. “This study provides no evidence to change my views that there are no meaningful nutritional differences between conventional produced and organic crops.”
The Alliance for Food for Food and Farming stands by the position that both organic and conventional fruits and vegetables are healthy and that the best thing people could do for their health is to eat more of either or both.
“Everyone seems to agree on this and we don’t understand how arguing which farming method is better is of any benefit to consumers,” said Marilyn Dolan, executive director of the Alliance. “Certainly, raising unnecessary concern among consumers about the safety of either system is not beneficial. Pitting one system against the other does not drive increased consumption of fruits and vegetables, which is what we need to be doing.”
On her blog, Food Politics, Marion Nestle also noted that the Newcastle study was not entirely independently funded. It was jointly funded by the EU’s European Framework 6 programme and the Sheepdrove Trust, which supports initiatives to increase organic farming and sustainability.
In addition, she suggested that the point of the study seems to be to prove organic foods are more nutritious for marketing purposes. “But most people who buy organics do so because they understand that organics are about production values,” she wrote. “As I said, if they are more nutritious, it’s a bonus, but there are plenty of other good reasons to prefer them.”
To critics who are not convinced that the extra antioxidants make a meaningful difference, Benbrook said “notice that they didn’t say ‘the science says it does not.’ They’re saying that it’s an open question.”
Benbrook acknowledge that other aspects of the diet will alter the response of an individual.
“With people who are eating their recommended six to eight servings of fruits and vegetables and are getting adequate antioxidants, another 20 percent isn’t going to make a big difference for them,” he said. “But people who are only getting two servings of fruits and vegetables and are probably getting less than half of their optimum daily antioxidant intake, a 20-40 percent increase for those individuals is going to translate into health benefits down the road.”