Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses.
Abstract: Demand for organic foods is partially driven by consumer perceptions that they are more nutritious. However, scientific opinion is divided on whether there are significant nutritional differences between organic and non-organic foods, and two recent reviews concluded that there are no differences. Here we report results of meta-analyses based on 343 peer-reviewed publications that indicate statistically significant, meaningful differences in composition between organic and non-organic crops/crop based foods. Most importantly, concentrations of a range of antioxidants such as polyphenolics were found to be substantially higher in organic crops/crop based foods, with levels of phenolic acids, flavanones, stilbenes, flavones, flavonols and anthocyanines being an estimated 19 (95% CI 5, 33), 69 (95% CI 13, 125), 28 (95% CI 12, 44), 26 (95% CI 3, 48), 50 (95% CI 28, 72) and 51 (95% CI 17, 86) % higher respectively.
Many of these compounds have been previously linked to reduced risk of chronic diseases, including cardiovascular and neurodegenerative diseases and certain cancers in dietary intervention and epidemiological studies. Additionally the frequency of occurrence of pesticide residues was 4 times higher in conventional crops, which also contained significantly higher concentrations of the toxic metal cadmium (Cd). Significant differences were also detected for some other compounds (e.g. minerals and vitamins). There is evidence that higher antioxidant and lower Cd concentrations are linked to specific agronomic practices (e.g. non-use of mineral N and P fertilisers respectively) prescribed in organic farming systems. Overall it is concluded that on average, across regions and production seasons, organic crops have more antioxidants and less Cd and pesticide residues than the non-organic comparators.
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