Published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods, according to findings reported in the Sept. 4 issue of the Annals of Internal Medicine. The review of the literature, led by researchers at Stanford University, did find eating organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.

The researchers investigated 17 studies in humans and 223 studies of nutrient and contaminant levels in foods. Only three of the human studies examined clinical outcomes, and they found no significant differences between populations by food type for allergic outcomes, including eczema, wheeze and atopic sensitization, or for symptomatic Campylobacter infection.

Two studies reported significantly lower urinary pesticide levels for children who ate organic diets when compared to children who ate conventional diets. In adults, studies of biomarker and nutrient levels in serum, urine, breast milk and semen did not identify clinical meaningful differences.

The risk for contamination with detectable pesticide residues was lower among organic produce than conventional produce by 30%. Differences in the risk for exceeding maximum allowed limits were small. E. coli contamination risk did not differ. The risk for isolating bacteria resistant to three or more antibiotics was higher in conventional chicken and pork than for organic chicken and pork by 33%.