By Helen Albert, Senior medwireNews Reporter
Strong evidence to support the supposed nutritional benefits of eating organic over conventional foods is lacking in the scientific literature, show results from a systematic review.
The team did find that levels of total phenols, which may have antioxidant properties, were higher in organic than in conventional foods, and that levels of omega-3 fatty acids were increased in organic compared with nonorganic milk and chicken. However, these differences were of no or only marginal statistical significance.
Similarly, phosphorous levels were marginally higher in organic over nonorganic food, but as very few people have phosphorous deficiency the researchers say this is unlikely to impact consumers greatly.
"Some believe that organic food is always healthier and more nutritious," said lead researcher Crystal Smith-Spangler (Stanford University, California, USA) in a press statement. "My colleagues and I were a little surprised that we didn't find that."
As reported in the Annals of Internal Medicine, the team selected 17 studies in humans and 223 studies of nutrient and contaminant levels in food for analysis.
Two studies in humans showed evidence for lower urinary pesticide levels in children eating organic rather than nonorganic food, and the risk for pesticide contamination was a significant 30% higher in conventional than in organic food. But, in general, levels were below government set maximum limits even in conventional foods.
Bacterial contamination did not differ significantly between organic and nonorganic food, although the chance of isolating bacteria that were resistant to three or more antibiotics was a significant 33% higher for conventional than organic food.
When asked about the implications of their research the authors say that they hope to educate and inform people rather than put them off buying organic food. They also recognize that the studies analyzed were heterogeneous in nature and suggest further research would be beneficial.
Co-author Dena Bravata, also from Stanford University, commented: "If you look beyond health effects, there are plenty of other reasons to buy organic instead of conventional." These include taste preferences, concern about the environmental impact of nonorganic food, and animal welfare.
Commenting on the findings, nutrition and public health expert Alan Dangour (London School of Hygiene and Tropical Medicine, UK) told the press: "Consumers select organic foods for a variety of reasons, however this latest review identifies that at present there are no convincing differences between organic and conventional foods in nutrient content or health-benefits. Hopefully this evidence will be useful to consumers."
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