Study: Organic Foods No More Nutritious than Conventional

A  recent review of research findings on organically produced foods and conventional foods found no differences in most nutrients — including vitamin C, calcium and iron. The review of 162 studies conducted over the last 50 years was commissioned by Britain's Food Standards Agency and appears in the American Journal of Clinical Nutrition.

From the abstract:

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. 

Alan D Dangour, Sakhi K Dodhia, Arabella Hayter, Elizabeth Allen, Karen Lock, Ricardo Uauy. Nutritional quality of organic foods: a systematic review. The American Journal of Clinical Nutrition, July 29, 2009.