It's a British study which makes me wonder what the differences are there between conventional and organic farming. Are those differences as substantial as in North America where factory farms compared with organic (which tend to be much smaller) would be farmed completely differently?
Another article mentions this:
"The appendix of the FSA report shows that some nutrients, such as beta-carotene, are as much as 53% higher in organic food, but such differences are not reflected in its conclusions."Source
So it looks like they ignored some of the facts in making their announcement.
It's an odd study since most people who buy organic food tend to do so not because of what's in it as because of what's not on it. People are trying to avoid pesticides, hormones, etc. People buy it because of concerns about animal welfare and sustainable farming practices. Any nutritional benefits would just be bonus.