British Journal of Nutrition

Full Papers

Dietary Surveys and Nutritional Epidemiology

Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses

Marcin Barańskia1, Dominika Średnicka-Tobera1, Nikolaos Volakakisa1, Chris Seala2, Roy Sandersona3, Gavin B. Stewarta1, Charles Benbrooka4, Bruno Biavatia5, Emilia Markelloua6, Charilaos Giotisa7, Joanna Gromadzka-Ostrowskaa8, Ewa Rembiałkowskaa8, Krystyna Skwarło-Sońtaa9, Raija Tahvonena10, Dagmar Janovskáa11, Urs Nigglia12, Philippe Nicota13 and Carlo Leiferta1 c1

a1 School of Agriculture, Food and Rural Development, Newcastle University, Nafferton Farm, Stocksfield, Northumberland, NE43 7XD, UK

a2 Human Nutrition Research Centre, School of Agriculture, Food and Rural Development, Newcastle University, Agriculture Building, Kings Road, Newcastle upon Tyne NE1 7RU, UK

a3 School of Biology, Newcastle University, Ridley Building, Newcastle upon Tyne NE1 7RU, UK

a4 Center for Sustaining Agriculture and Natural Resources, Washington State University, Pullman, WA, USA

a5 Department of Agricultural Sciences, School of Agriculture and Veterinary Medicine, University of Bologna, Viale Fanin 42, 40127 Bologna, Italy

a6 Department of Pesticide Control and Phytopharmacy, Benaki Phytopathological Institute, GR 14561 Kifissia, Athens, Greece

a7 Department of Organic Farming and Food Technology, Technological Educational Institute of Ionian Islands, Iosif Momferatou & Ilia Miniati PC 28100, Argostoli, Cephalonia, Greece

a8 Faculty of Human Nutrition and Consumer Sciences, Warsaw University of Life Sciences, Nowoursynowska 159c, 02-776 Warsaw, Poland

a9 Department of Animal Physiology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland

a10 Biotechnology and Food Research, MTT Agrifood Research Finland, FI-31600 Jokioinen, Finland

a11 Department of Gene Bank, Crop Research Institute (CRI), Drnovská 507/73, 161 06 Praha 6 – Ruzyně, Czech Republic

a12 Research Institute of Organic Agriculture (FiBL), Ackerstrasse 113, CH-5070 Frick, Switzerland

a13 INRA, UR407 Pathologie végétale, 67 allée des chênes, F-84143 Montfavet Cedex, France

Abstract

Demand for organic foods is partially driven by consumers' perceptions that they are more nutritious. However, scientific opinion is divided on whether there are significant nutritional differences between organic and non-organic foods, and two recent reviews have concluded that there are no differences. In the present study, we carried out meta-analyses based on 343 peer-reviewed publications that indicate statistically significant and meaningful differences in composition between organic and non-organic crops/crop-based foods. Most importantly, the concentrations of a range of antioxidants such as polyphenolics were found to be substantially higher in organic crops/crop-based foods, with those of phenolic acids, flavanones, stilbenes, flavones, flavonols and anthocyanins being an estimated 19 (95 % CI 5, 33) %, 69 (95 % CI 13, 125) %, 28 (95 % CI 12, 44) %, 26 (95 % CI 3, 48) %, 50 (95 % CI 28, 72) % and 51 (95 % CI 17, 86) % higher, respectively. Many of these compounds have previously been linked to a reduced risk of chronic diseases, including CVD and neurodegenerative diseases and certain cancers, in dietary intervention and epidemiological studies. Additionally, the frequency of occurrence of pesticide residues was found to be four times higher in conventional crops, which also contained significantly higher concentrations of the toxic metal Cd. Significant differences were also detected for some other (e.g. minerals and vitamins) compounds. There is evidence that higher antioxidant concentrations and lower Cd concentrations are linked to specific agronomic practices (e.g. non-use of mineral N and P fertilisers, respectively) prescribed in organic farming systems. In conclusion, organic crops, on average, have higher concentrations of antioxidants, lower concentrations of Cd and a lower incidence of pesticide residues than the non-organic comparators across regions and production seasons.

(Received September 11 2013)

(Revised May 02 2014)

(Accepted May 06 2014)

(Online publication July 15 2014)

Key Words:

  • Organic foods;
  • Conventional foods;
  • Composition differences;
  • Antioxidants/(poly)phenolics

Correspondence

c1 Corresponding author: Professor C. Leifert, fax +44 1661 831 006, email carlo.leifert@newcastle.ac.uk

Footnotes

  Abbreviations: BS, basket study; CF, comparison of matched farms; EX, controlled field experiment; GRADE, Grading of Recommendations, Assessment, Development and Evaluation; MPD, mean percentage difference; MRL, maximum residue level; SMD, standardised mean difference

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