In the largest study of its kind, an international team of experts led by Newcastle University, UK, has shown that organic food is up to 69% higher in a number of key antioxidants than conventionally-grown crops.
Analysing 343 studies into the compositional differences between organic and conventional crops, the team found that a switch to eating organic fruit, vegetable and cereals – and food made from them – would provide additional antioxidants equivalent to eating between 1-2 extra portions of fruit and vegetables a day.
The study, published this week in the British Journal of Nutrition, also shows significantly lower levels of toxic heavy metals in organic crops. Cadmium, which is one of only three metal contaminants along with lead and mercury for which the European Commission has set maximum permitted contamination levels in food, was found to be almost 50% lower in organic crops than conventionally-grown ones.
Newcastle University’s Professor Carlo Leifert, who led the study, says: “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. “This constitutes an important addition to the information currently available to consumers which until now has been confusing and in many cases is conflicting.”
Welcoming the report, Helen Browning, the Soil Association chief executive, commented: “The crucially important thing about this research is that it shatters the myth that how we farm does not affect the quality of the food we eat. The research found significant differences, due to the farming system, between organic and non-organic food.
“The crucially important thing about this research is that it shatters the myth that how we farm does not affect the quality of the food we eat”
“We know that people choose organic food because they believe it is better for them, as well as for wildlife, animal welfare and the environment, and this research backs up what people think about organic food.
“In other countries there has long been much higher levels of support and acceptance of the benefits of organic food and farming: we hope these findings will bring the UK in line with the rest of Europe, when it comes to both attitudes to organic food and support for organic farming.”
The Newcastle University report draws on the most extensive analysis of the nutrient content in organic vs conventionally-produced foods ever undertaken and is the result of a groundbreaking new systematic literature review and meta-analysis by the international team.
The findings contradict those of a 2009 UK Food Standards Agency (FSA) commissioned study which found there were no substantial differences or significant nutritional benefits from organic food.
The FSA commissioned study based its conclusions on only 46 publications covering crops, meat and dairy, while Newcastle led meta-analysis is based on data from 343 peer-reviewed publications on composition difference between organic and conventional crops now available.
“The main difference between the two studies is time,” explains Professor Leifert, who is Professor of Ecological Agriculture at Newcastle University. “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”. Dr Gavin Stewart, a Lecturer in Evidence Synthesis and the meta-analysis expert in the Newcastle team, added: “The much larger evidence base available in this synthesis allowed us to use more appropriate statistical methods to draw more definitive conclusions regarding the differences between organic and conventional crops”
The Newcastle University study, funded jointly by the European Framework 6 programme and the Sheepdrove Trust, found that concentrations of antioxidants such as polyphenolics were between 18-69% higher in organically-grown crops.
Numerous studies have linked antioxidants to a reduced risk of chronic diseases, including cardiovascular and neurodegenerative diseases and certain cancers.
“The organic vs non-organic debate has rumbled on for decades now but the evidence from this study is overwhelming”
Substantially lower concentrations of a range of the toxic heavy metal cadmium were also detected in organic crops (on average 48% lower), while pesticide residues were four times more likely to be found in conventional crops than organic ones.
Professor Leifert added: “The organic vs non-organic debate has rumbled on for decades now but the evidence from this study is overwhelming – that organic food is high in antioxidants and lower in toxic metals and pesticides.
“But this study should just be a starting point. We have shown without doubt there are composition differences between organic and conventional crops, now there is an urgent need to carry out well-controlled human dietary intervention and cohort studies specifically designed to identify and quantify the health impacts of switching to organic food.”
Key findings by Newcastle University were:
- Farming method affects quality: The analysis is the most extensive and reliable to date and clearly supports the view that the quality of food is influenced by the way it is produced.
- More antioxidants: Organic crops (cereals, fruit and vegetables) have significantly higher concentrations of antioxidants/(poly)phenolics compared with non-organic produced counterparts. This includes more phenolics (19% higher), flavanones (69% higher), stilbenes (28% higher), flavones (26% higher), and flavonols (50% higher). A switch to consuming organic crops would allow a 20-40% increase in antioxidant/(poly)phenolics consumption without an increase in calorie intake.
- Fewer pesticides: The frequency of occurrence of detectable pesticide residues is four times higher in non-organic crops. Non-organic fruit had the highest pesticide frequency (75%), compared to non-organic vegetables (32%) and non-organic crop based processed foods (45%). By contrast pesticide residues were found in 10% of organic crop samples.
- Less cadmium: The analysis detected 48% lower concentrations of the toxic heavy metal cadmium in organic crops.
- Less nitrogen: Nitrogen concentrations – linked in some studies to an increased risk of certain cancers such as stomach cancer – were found to be significantly lower in organic crops.