01.Organic food research limitations
Experts are critical of a new study which found organic foods have higher concentrations of antioxidants than conventionally grown crops.
A UK meta-analysis of 343 studies concluded that organic crops and crop-based foods are between 19% and 69% higher in certain antioxidants than conventionally grown crops. Organic crops also had lower concentrations of the heavy metal cadmium and a lower incidence of pesticide residues reported the study, published in the British Journal of Nutrition.
But although this is a large study which considers all available published evidence it has limitations which cast doubt over its conclusions, according to experts.
Dr Alan Dangour, Reader in Food and Nutrition for Global Health at the London School of Hygiene and Tropical Medicine, explains "The quality of the available data varies greatly and it is therefore very surprising that, in their analysis, the authors decided to include all the data that they found, irrespective of their quality. In fact the study authors themselves note that there are significant concerns with the consistency and reliability of some of their findings. Mixing good quality data with bad quality data in this way is highly problematic and significantly weakens confidence in the findings of the current analysis."
Antioxidant claims overstated
The study also claims that many of the antioxidants it found to be higher in organic crops and crop-based foods have been linked to a reduced risk of chronic diseases, including certain cancers. This is misleading, according to Professor Tom Sanders, Head of Diabetes and Nutritional Sciences Division, School of Medicine, King's College London. "While the World Cancer Research Fund in its systematic reviews concluded there is a relationship between fruit and vegetable consumption and a lower risk of cancer, they did state that there was insufficient evidence to make any claim for antioxidants and plant phenolics," he says.
Other experts agree. "The public health significance of the reported findings have been worryingly overstated. There is no good evidence to suggest that slightly greater antioxidant or polyphenolic intake in the human diet has important public health benefits, and there is no robust evidence to support the claim that consumption of greater amounts of these compounds reduces the risk of chronic diseases such as cardiovascular disease and cancer in human populations," says Dangour.
Questions raised over cadmium finding
A question mark has even been raised over the finding that the levels of toxic metal cadmium were lower in organic cereals than conventional foods. "Cadmium levels are dependent on the soil in which the plant is grown and have nothing to do with organic certification," asserts Sanders.
The critics’ opinion of the research is summed up by Dr Ian Musgrave, Senior Lecturer in the Faculty of Medicine, School of Medicine Sciences, within the Discipline of Pharmacology at the University of Adelaide. “This is yet another study that shows that there is little difference in nutritional content between organically grown food and conventionally grown food.
"Given their much higher price, people need to carefully consider any decision to consume organic foods," he says.
According to the UK’s Catherine Collins, Principal Dietitian at St George’s Hospital NHS Trust, the take-home message for consumers is to focus on the bigger picture, "It’s worth remembering that all of the massive national, European and international studies showing the significant health benefits of eating at least 5 portions of fruit and vegetables daily have never made a distinction between organic and non-organic varieties. When it comes to health insurance all fruits and vegetables count. Bottom line? Just eat more."