Effect of dietary advice to increase fruit and vegetable consumption on plasma flavonol concentrations: results from a randomised controlled intervention trial

A recent meta-analysis of prospective cohort studies suggests that high dietary intakes of flavonols are associated with a significantly lower risk of coronary heart disease mortality.1 The major dietary sources of flavonols such as quercetin, kaempferol, and isorhamnetin are tomatoes, onions, kale, broccoli, celery, apples, and cherries, while catechins are concentrated in tea and red wine.2,3 No clinical trials have examined the effect of interventions to increase habitual fruit and vegetable intake on plasma flavonol concentrations in free living populations. As the principal dietary sources of flavonols are restricted to a few specific food types, it is uncertain whether general dietary advice to increase fruit and vegetable consumption will increase plasma flavonol concentrations. We conducted a randomised controlled trial to investigate the effect over six months of an intervention to increase fruit and vegetable intake in a free living population and investigated what impact this intervention had on plasma concentrations of flavonols.4