A study published in the British Journal of Nutrition shows that organic foods and crops may have more antioxidants and fewer, less frequent pesticide residues than their conventional counterparts. The study looked at 343 peer-reviewed publications comparing the nutritional quality and safety of organic and conventional plant-based foods, including fruits, vegetables, and grains. The researchers applied meta-analysis techniques to quantify differences between organic and non-organic foods. Most of the publications covered in the study looked at crops grown in the same area on similar soils.
The research team found the quality and reliability of comparison studies has greatly improved in recent years, leading to the discovery of nutritional and food safety differences not detected in earlier studies. The researchers found that overall organic crops had 18–69% higher concentrations of antioxidant compounds. Specifically, the organic crops had 19% more phenolic acids, 69% more flavanones, 28% more stilbenes, 26% more flavones, 50% more flavonols, and 51% more anthocyanins.
The researchers also found pesticide residues were three to four times more likely in conventional foods than organic ones, as organic farmers are not allowed to apply synthetic pesticides. While crops harvested from organically-managed fields sometimes contain pesticide residues, the levels are usually 10-fold to 100-fold lower in organic food, compared to the corresponding, conventionally grown food. Specifically, the researchers found that conventional crops had roughly twice as much cadmium, a toxic heavy metal contaminant, as organic crops. They hypothesized that certain fertilizers approved for use only on conventional farms somehow make cadmium more available to plant roots.