New research, based on an analysis of several hundred studies, has cast doubt on arguments that organically grown foods are more nutritious than conventionally grown foods.
The study, published in Annals of Internal Medicine, is the most comprehensive meta-analysis to date of existing studies comparing organic and conventional foods. Researchers analysed 237 separate studies which compared the organic foods to conventionally grown foods. They did not find strong evidence that organic foods are more nutritious or carry fewer health risks than conventional alternatives, though consumption of organic foods can reduce the risk of pesticide exposure.
As for what the findings mean for consumers, the researchers said their aim is to educate people, not to discourage them from making organic purchases. “If you look beyond health effects, there are plenty of other reasons to buy organic instead of conventional,” noted lead researcher Dena Bravata, from Stanford University. She listed taste preferences and concerns about the effects of conventional farming practices on the environment and animal welfare as some of the reasons people choose organic products.
Registered journalists can access the full study and press material in the SMC Resource Library.
Our colleagues at the UK SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).
Prof Alan Dangour, Senior Lecturer at the Nutrition and Public Health Intervention Research Unit, London School of Hygiene and Tropical Medicine, said:
“The Smith-Spangler paper is a careful and detailed review of reports comparing the nutrient and health-related qualities of organic and conventional foods published since 1966. Like our 2009 review (attached), it again demonstrates that there are no important differences in nutrient content between organic and conventionally produced foods. The Smith-Spangler paper also reviews health benefits of organic foods and like our 2010 review (attached) finds no evidence that organic foods are healthier than conventionally produced foods. The Smith-Spangler paper extends our earlier work by reviewing pesticide and bacterial content of organically and conventionally produced foods and highlights some interesting results.
“However, throughout the paper the authors make it clear that the evidence base is weak and highly variable i.e. there is no consistent signal from the data supporting the nutritional or health-related superiority of organic foods. In general there is a need to strengthen the quality of research and reporting in this area.
“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.”
From the AusSMC:
Liza Oates is currently conducting a PhD in the health effects of organic diets and is course coordinator of Food as Medicine, Wellness & Complementary and Alternative Medicine for the Master of Wellness Program at RMIT University. She comments:
“In terms of the perceived health benefits of organic foods, the majority of people who eat organic food are driven by risk aversion not nutritional superiority.
“Our research shows organic consumers are more interested in what’s not in their food – such as pesticides and antibiotics – than what is. Most also say that the environmental and social benefits of organic food play a key role in their decision to go organic.
“This review has confirmed that organic foods have lower levels of pesticide residues and antibiotic-resistant bacteria. The fact that they failed to find strong evidence that organic foods have more nutrients is relatively predictable.
“There are a huge number of factors that affect nutrient levels in food. So it is almost inevitable that trying to isolate one factor, such as farming method, to explain these nutritional differences will be problematic. This is exacerbated when researchers attempt to make generalisations by pooling the results from hundreds of studies that were conducted on different nutrients, in different foods, grown in different regions and during different growing seasons.
“Research in the US has shown that eating organic food has a dramatic effect on pesticide residues in children. Substituting non-organic fruits and vegetables with organics for five days resulted in an almost complete reduction in organophosphate pesticide residues. It is this kind of benefit that many organic consumers are looking for when choosing to buy organic food.”