There is clear evidence that organic foods are cleaner and have higher nutritional quality. Organic foods are higher in antioxidants, and lower in metallic toxins and pesticides, according to a report in a scientific review by Baranski et al., (2014)  .
The extensive article published in the British Journal of Nutrition examined a total of 343 research studies from 1992-2011, which included comparisons of fruit, vegetables and compound foods. The researchers found that compared to conventional foods, organic foods were cleaner, as indicated by being lower in the toxic metals – cadmium and strontium, lower in pesticide residues, and lower in nitrogen from fertilizers, across all food types.
In terms of nutritional value, organic foods were higher in more than 5 different classes of antioxidants, including carotenoids, total antioxidants, and higher in vitamin C content.
This increase in vitamin C was also reported in an earlier study Worthington (2001) . This researcher analysed 41 earlier research studies, focusing on those organic processes that didn’t use any fertilizers. Vitamin C levels were on average 27% higher in organic vs conventional foods.
Other nutrients that were statistically higher included iron (21%), magnesium (29%) and phosphorus (13%). There were also trends towards increases in all other trace mineral, especially iodine (498%), molybdenum (152%), chromium (86%) and selenium (372%), however these averages were more variable.
Worthington noted that levels of heavy metals including cadmium, were generally lower in organic fruit and vegetables, compared to conventionally grown ones.