Nutritional quality of organic foods: a systematic review 1,2,3,4
Alan D Dangour, Sakhi K Dodhia, Arabella Hayter, Elizabeth Allen, Karen Lock and Ricardo Uauy
1 From the Nutrition and Public Health Intervention Research Unit (ADD, SKD, AH, and RU) and the Medical Statistics Unit (EA), Department of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom, and the Health Services Research Unit, Department of Public Health and Policy, London School of Hygiene & Tropical Medicine, London, UK (KL).
2 The funding organization had no role in the study design, data collection, analysis, interpretation, or writing of the report. The review team held 6 progress meetings with the funding organization.
3 Supported by the UK Food Standards Agency (PAU221).
4 Address correspondence to AD Dangour, Nutrition and Public Health Intervention Research Unit, Department of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom. E-mail: email@example.com.
Background: Despite growing consumer demand for organically produced foods, information based on a systematic review of their nutritional quality is lacking.
Objective: We sought to quantitatively assess the differences in reported nutrient content between organically and conventionally produced foodstuffs.
Design: We systematically searched PubMed, Web of Science, and CAB Abstracts for a period of 50 y from 1 January 1958 to 29 February 2008, contacted subject experts, and hand-searched bibliographies. We included peer-reviewed articles with English abstracts in the analysis if they reported nutrient content comparisons between organic and conventional foodstuffs. Two reviewers extracted study characteristics, quality, and data. The analyses were restricted to the most commonly reported nutrients.
Results: From a total of 52,471 articles, we identified 162 studies (137 crops and 25 livestock products); 55 were of satisfactory quality. In an analysis that included only satisfactory quality studies, conventionally produced crops had a significantly higher content of nitrogen, and organically produced crops had a significantly higher content of phosphorus and higher titratable acidity. No evidence of a difference was detected for the remaining 8 of 11 crop nutrient categories analyzed. Analysis of the more limited database on livestock products found no evidence of a difference in nutrient content between organically and conventionally produced livestock products.
Conclusions: On the basis of a systematic review of studies of satisfactory quality, there is no evidence of a difference in nutrient quality between organically and conventionally produced foodstuffs. The small differences in nutrient content detected are biologically plausible and mostly relate to differences in production methods.