Purpose Limited robust randomised controlled trials investigating fruit and vegetable (F&V) intake in people at risk of cardiovascular disease (CVD) exist. We aimed to design and validate a dietary strategy of increasing flavonoid-rich versus flavonoid-poor F&V consumption on nutrient biomarker profile.Methods A parallel, randomised, controlled, dose–response dietary intervention study. Participants with a CVD relative risk of 1.5 assessed by risk scores were randomly assigned to one of the 3 groups: habitual (control,CT), high-flavonoid (HF) or low-flavonoid (LF) diets.While the CT group (n = 57) consumed their habitual diet throughout, the HF (n = 58) and LF (n = 59) groups sequentially increased their daily F&V intake by an additional 2, 4 and 6 portions for 6-week periods during the18-week study.Results Compliance to target numbers and types of F&Vwas broadly met and verified by dietary records, and plasma and urinary biomarkers. Mean (±SEM) number of F&Vportions/day consumed by the HF and LF groups at baseline(3.8 ± 0.3 and 3.4 ± 0.3), 6 weeks (6.3 ± 0.4 and 5.8 ±0.3), 12 weeks (7.0 ± 0.3 and 6.8 ± 0.3) and 18 weeks(7.6 ± 0.4 and 8.1 ± 0.4), respectively, was similar at baseline yet higher than the CT group (3.9 ± 0.3, 4.3 ± 0.3,4.6 ± 0.4, 4.5 ± 0.3) (P = 0.015). There was a dose dependent increase in dietary and urinary flavonoids in the HF group, with no change in other groups (P = 0.0001).Significantly higher dietary intakes of folate (P = 0.035),non-starch polysaccharides (P = 0.001), vitamin C (P =0.0001) and carotenoids (P = 0.0001) were observed in both intervention groups compared with CT, which were broadly supported by nutrient biomarker analysis.Conclusions The success of improving nutrient profile by active encouragement of F&V intake in an intervention study implies the need for a more hands-on public health approach.