Effects of fruit and vegetable consumption on plasma antioxidant concentrations and blood pressure: A randomised controlled trial
John JH., Ziebland S., Yudkin P., Roe LS., Neil HAW.
Background: High dietary intakes of fruit and vegetables are associated with reduced risks of cancer and cardiovascular disease. Short-term intensive dietary interventions in selected populations increase fruit and vegetable intake, raise plasma antioxidant concentrations, and lower blood pressure, but long-term effects of interventions in the general population are not certain. We assessed the effect of an intervention to increase fruit and vegetabl e consumption on plasma concentrations of antioxidant vitamins, daily fruit and vegetable intake, and blood pressure. Methods: We undertook a 6-month, randomised, controlled trial of a brief negotiation method to encourage an increase in consumption of fruit and vegetables to at least five daily portions. We included 690 healthy participants aged 25-64 years recruited from a primary-care health centre. Findings: Plasma concentrations of α-carotene, β-carotene, lutein, β-cryptoxanthin, and ascorbic acid increased by more in the intervention group than in controls (significance of between-group differences ranged from p=0.032 to 0.0002). Groups did not differ for changes in lycopene, retinol, α-tocopherol, γ-tocopherol, or total cholesterol concentrations. Self-reported fruit and vegetable intake increased by a mean 1.4 (SD 1.7) portions in the intervention group and by 0.1 (1.3) portion in the control group (between-group difference=1.4, 95% CI 1.2-1.6; p < 0.0001). Systolic blood pressure fell more in the intervention group than in controls (difference=4.0 mm Hg, 2.0-6.0; p < 0.0001), as did diastolic blood pressure (1.5 mm Hg, 0.2-2.7; p=0.02). Interpretation: The effects of the intervention on fruit and vegetable consumption, plasma antioxidants, and blood pressure would be expected to reduce cardiovascular disease in the general population.