An international team of experts led by Newcastle University, UK, has proved that organic crops and crop-based foods are up to 60% higher in a number of key antioxidants than conventionally-grown crops. Published in the British Journal of Nutrition, the largest study of its kind found that switching to eating organic fruit, vegetables and cereals would provide additional antioxidants equivalent to eating between one and two extra portions of fruit and vegetables. It also showed drastically lower levels of toxic heavy metals in organic crops.

 Newcastle University’s Professor Carlo Leifert, who led the study, explains: “This constitutes an important addition to the information currently available to consumers which until now has been confusing and in many cases is conflicting.”  The analysis indicates that the quality of food is strongly influenced by the way it is produced. In particular, there is increasing evidence that higher levels of manufactured chemical fertilisers, most notably the nitrogen and phosphate-based fertilisers that are prohibited or heavily restricted by organic farming standards, lead to the substantially lower concentrations of antioxidants in conventional crops.

Organic crops and crop-based food products were found to have higher concentrations of antioxidants (including phenolic acids, flavanones, stilbenes, flavones, flavonols and anthocyanines) compared with their conventionally produced counterparts. The mean percentage difference for most antioxidant compounds was between plus 18% and 69%. Smaller, but still statistically significant, composition differences were also detected for a number of carotenoids and vitamins. A switch to eating organic fruit, vegetables and cereals (and food made from them) would lead to a 20–40% (and for some compounds up to a 60%) increase in crop-based antioxidant (poly)phenolic consumption without any increase in calories. The increased consumption of (poly)phenolics and other plant secondary metabolites with antioxidant activity protects against chronic diseases, including cardiovascular and neurodegenerative diseases and some cancers.
 
Lower concentrations of a range of toxic heavy metals were detected inorganic crops, particularly cadmium (on average 48% lower). Cadmium is one of only three toxic metal contaminants along with lead and mercury for which the European Commission has set maximum permitted contamination levels in food. Any reduction in cadmium consumption is positive, since it is known to accumulate in the body. Nitrogen concentrations were also found to be lower in organic crops. Concentrations of total nitrogen were 10%, nitrate 30% and nitrite 87% lower in organic compared with conventional crops. The higher nitrate and nitrite concentrations in conventional crops are believed to be linked to the use of mineral nitrogen fertiliser, which is strictly banned under organic farming standards. The higher nitrite concentrations in conventional crops can be considered nutritionally undesirable, as they have been described as potential risk factors for stomach cancer and other conditions.
 
The study found that the frequency of the occurrence of detectable pesticides is four times higher in conventional than organic crops. Conventionally grown fruit had by far the highest frequency of pesticide residues, about seven times higher than in organic fruit. In conventional vegetables and crop-based processed foods the frequency of pesticide residues was three to four times higher than in organic. All organic crop types were found to have similarly low contamination rates.

While further studies are needed to clarify the health benefits of reducing pesticide exposure, any reduction can be considered desirable, especially since a significant proportion of conventional crop samples regulated by the European Food Safety Authority(EFSA) contain pesticide residues above permitted levels. In recent EFSA surveys pesticide residues above the Maximum Residue Levels were found in spinach, oats, peaches, oranges, strawberries and lettuce, table grapes and apple samples, among others.
 
The study identified serious deficiencies in a large proportion of previously published studies. These include a lack of standardised measurements and reporting, and evidence of duplicative or selective reporting of data collected in experiments. The authors of the Newcastle University study concluded that further research is needed to understand the variation between studies and that it is vital that future comparative food composition studies use standardised protocols.

 The findings of “Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses” 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 the Newcastle-led meta-analysis is based on data from 343 peer-reviewed publications on the composition difference between organic and conventional crops now available.

This study is 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 around Professor Carlo Leifert. It was started under the European Sixth Framework Programme projectQualityLowInputFood and completed later with funding from theSheepdrove Trust. The entire database generated and used for this analysis is freely available on the Newcastle University website for the benefit of other experts and interested members of the public here.

Source: NCU