Organic tomatoes have significantly higher levels of flavonoids, compared to non-organic tomatoes, according to the results of a ten-year study carried out by researchers at the University of California.

You can read about this study in a report coming out soon in the Journal of Agricultural Food Chemistry.

Flavanoids are a class of water-soluble pigments that are present in many plants. Scientists have identified a few thousand different flavonoids. Flavonoids are known to lower hypertension (high blood pressure), thus lowering heart disease and stroke risk. Studies have also indicated that flavonoids may protect us to some extent from cancer and dementia.

The researchers believe that it is the quality of the soil that gives the organic tomatoes their higher flavonoid levels, specifically, the absence of fertilizers.

In this study, the researchers measured the amounts of quercetin and kaempferol, two flavonoids, in dried tomato samples. They found that levels of quercetin were 79% higher, and kaempferol 97% higher in the organic tomatoes, compared to the non-organic ones.

When nitrogen levels are not high enough in the soil, plants produce flavanoids as a defence mechanism. If inorganic nitrogen, which is present in everyday fertilizers, are applied to the soil, this over-fertilization may hinder flavonoid production.

"Organic tomatoes have more antioxidants"
Duncan Graham-Rowe
The New Scientist
Click here to see article

Useful link:
-- What is organic? - The Soil Association