Organic onions may have more antioxidant activity, higher flavonol content

A study published in Journal of Agricultural and Food Chemistry suggests that organic onions may have more antioxidant activity and higher flavonol content than conventional onions. For the study, the research team grew two onion varieties—Red Baron and Hyskin—in a variety of conditions between 2009 and 2014.

They grew the crops under four treatment combinations—fully organic, fully conventional, and two mixed treatment (organic soil with conventional pest control, and vice versa). “Conventional agriculture” was defined as conventional treatment of soil (i.e., mineral fertilizers, no fixed crop rotation) with conventional pest control (i.e., chemical weed-killers and other pesticides). “Organic agriculture” was defined as organic treatment of soil (i.e., organic fertilizers, crop rotations, cover crops) with organic methods for pest control (i.e., mechanical weeding, mechanical methods, or certified organic methods to control pests).

They analyzed levels of antioxidants and other compounds associated with various health benefits, and found higher antioxidant levels in both types of onions when grown using organic practices. The organic onions also had up to 20% higher flavonol content than the conventional crop. The researchers attributed the differences mainly to different soil management practices. Interestingly, the authors also showed that external variables, such as weather and even global radiation, had impacts on flavonoid content as well—which means they may also have played a role but not been accounted for in previous studies evaluating organic and conventional produce.

Study author Kim Reilly concluded that the study “shows that how we treat the soil can affect the soil microbiome, and how in turn that can affect the food we eat and human health.”

Abstract