Human Health and Organic Foods – A Review

Abstract: The purpose of this study is to review evidence comparing the health effects of organic and conventional foods. English-language reports of comparisons of organically and conventionally grown food or of populations consuming these foods were reviewed. Two independent investigators extracted data on methods, health outcomes, and nutrient and contaminant levels. Seventeen studies in humans and 223 studies of nutrient and contaminant levels in foods met inclusion criteria. Only three of the human studies examined clinical outcomes, finding no significant differences between populations by food type for allergic outcomes (eczema, wheeze, atopic sensitization) or symptomatic Campylobacter infection. Two studies reported significantly lower urinary pesticide levels among children consuming organic verses conventional diets, but studies of biomarker and nutrient levels in serum, urine, breast milk and semen in adults did not identify clinically meaningful differences. All estimates of differences in nutrient and contaminant levels in foods were highly heterogeneous except for the estimate for phosphorus; phosphorus levels were significantly higher than in conventional produce, although this difference was not clinically significant. The risk for contamination with detectable pesticide residues was lower among organic than conventional produce (risk difference, 30% [CI, -37% to -23%]), but differences in risk for exceeding maximum allowed limits were small. Escherichia coli contamination risk did not differ between organic and conventional produce. Bacterial contamination of retail chicken and pork was common but unrelated to farming method. However, the risk for isolating bacteria resistant to 3 or more antibiotics was higher in conventional than in organic chicken and pork  (risk difference, 33% [CI, 21% to 45%]). Limitation: Studies were heterogeneous and limited in number, and publication bias may be present. Conclusion: The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria. © American College of Physicians.

Reference: Crystal, Smith-Spangler, et. al. (2012). Are organic foods safer or healthier than conventional alternatives? A systematic review. Annuals of Internal Medicine 157(5): 348-366. Available online at:  

Related article: Holzman, D. C. (2012). Organic Food Conclusions Don't Tell the Whole Story. Environmental Health Perspectives, 120(12): A458. Available online at: