Levels of flavonoids increase over time in crops grown in organically farmed fields, according to a rare long-term study scheduled for publication in the July 18 issue of ACS’ Journal of Agricultural and Food Chemistry, a bi-weekly publication.

Other research has suggested that consumption of flavonoids may protect against cancer, heart disease, and other age-related diseases.

In the new study, Alyson E. Mitchell and colleagues compared levels of key flavonoids in tomatoes harvested over a 10-year period from two matched fields — one farmed organically and the other with conventional methods that included commercial fertilizers. The research focused on tomatoes because per capita consumption in the United States is so high, second only to potatoes. Researchers analyzed organic and conventional tomatoes that had been dried and archived under identical conditions from 1994 to 2004.

“The levels of flavonoids increased over time in samples from organic treatments, whereas the levels of flavonoids did not vary significantly in conventional treatments,” their report stated.

Increases corresponded with the accumulation of soil organic matter in organic plots and with reduced fertilization rates. “Well-quantified changes in tomato nutrients over years in organic farming systems have not been reported previously.”