Effect of Diet on Flavonoids and Antioxidative Defense

Background and methodology:

Flavonoids are a group of polyphenolic secondary metabolites that occur in all plants and are an integral part of the human diet. Different food production methods may result in differences in the content of secondary metabolites. This study compared diets of conventionally and organically produced foods in a human crossover intervention study with respect to the intake and excretion of five selected flavonoids and their effect on markers of oxidative defense.  


The urinary excretion of quercetin and kaempferol was higher after 22 days in the organic diet. The excretions of flavonoids in urine as a percentage of intake were similar after both interventions. Most markers of antioxidative defense did not differ between the diets, but the organic diet resulted in an increased protein oxidation and a decreased total plasma antioxidant capacity compared to baseline. The growing conditions of fruits and vegetables (conventional vs. organic) affected the foods’ flavonoid content, resulting in urinary excretion of major dietary flavonoids.  Also, markers of antioxidative defense were affected by the food production method. Because selection of more resistant varieties is of central importance to organic farming, it cannot be excluded that the observed effects originated from the differences between the organic and conventional diets, rather than from the differences in handling and pesticide use in the two different production systems.


Grinder-Pedersen, L., Rasmussen, S. E., Bugel, S., Jorgensen, L.V., Dragsted, L. O., Gundersen, V., & Sandstrom, B. (2003). Effect of diets based on foods from conventional versus organic production on intake and excretion of flavonoids and markers of antioxidative defense in humans. Journal of Agricultural and Food Chemistry, 51(19), 5671-5676. Available on-line:http://pubs.acs.org/doi/full/10.1021/jf030217n