If you have any doubts about the value of organic foods vs. conventionally-grown foods, then take a look at the findings from a USDA--Yes, USDA --sponsored study.
In this study, the nutritional content of organic vs. conventionally-grown blueberries were compared. Ironically, these observations come from the USDA's Genetic Improvement of Fruits and Vegetables Laboratory of the Produce Quality and Safety Laboratory.
Their findings (all values expressed as weight per 100 grams fresh weight blueberries, or a bit less than 1/4 cup):
Total phenol content (e.g, flavonoids):
Organic: 319.3 mg
Conventional: 190.3 mg
Organic blueberries had 68% greater phenol content.
Total anthocyanins (an important class of flavonoids):
Organic: 131.2 mg
Conventional: 82.4 mg
Organic blueberries had 59% greater anthocyanin content.
Antioxidant capacity (ORAC):
Organic: 46.14 mg
Conventional: 30.8
Organic blueberries had 50% greater antioxidant capacity.
Flavonoids suspected to carry unusually potent health effects--malvidin, delphinidin, myricetin, and quercetin--were all contained in greater proportions in the organically-grown blueberries, also. These flavonoids are demonstrating pharmacologic-level health effects in preliminary studies.
Why a genetics laboratory? After all , the study findings came out heavily in favor of non-genetic, organic farming methods of growing produce. It certainly must have at least given pause to the vocal group within agriculture and the USDA that have long argued that organic produce is no different. I suspect that the laboratory will now try to recreate the nutritional value of organic through genetic manipulation of cultivars grown using conventional methods.
Regardless of the motivations behind the study, we see that there is no comparison: organic blueberries are superior in nutritional value to those grown with conventional pesticides and herbicides. While the study addressed only blueberries, the dramatic difference makes it likely that similar differences exist in other fruits and vegetables.
Coming on the Track Your Plaque website: An in-depth Special Report on the health effects of anthocyanins.