Organic Agriculture and Nutritional Value of Plant Foods

Background and methodology:

Proponents of organic agriculture often claim that organically produced plant foods promote health of humans than products from conventional production systems. Opponents argue that owing to inadequate nutrition of the plants and lack of protection against diseases, organic products are supposed to contain less protein, sugars and vitamins and have increased levels of defense-related secondary metabolites, which are in this case considered harmful owing to similarities to pesticides and other poisons. What is the reality?  
Findings:

The study concluded that nutritionally important differences relating to contents of minerals, vitamins, proteins and carbohydrates are not likely, primarily since none of these are deficient in typical First World diets, nor are present levels of pesticides residues in conventional products a cause for concern. There is reason however to believe that contents of many defense-related secondary metabolites in the diet are lower than optimal for human health, even for those where too high levels are known to be harmful. There is ample, but circumstantial evidence that, on average, organic vegetables and fruits most likely contain more of these compounds than conventional ones, allowing for the possibility that organic plant foods may in fact benefit human health more than corresponding conventional ones.

Reference:
Brandt, K. & Mølgaard, J. P. (2001). Organic agriculture: does it enhance or reduce
the nutritional value of plant foods? Journal of the Science of Food and Agriculture 81:924-931.