Previous research has shown that 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.
However, longer-term effects of interventions in the general population are unknown.
Andrew Neil and colleagues from the University of Oxford, England, assessed the effect of a 6-month intervention to increase fruit and vegetable consumption on plasma concentrations of antioxidant vitamins, daily fruit and vegetable intake, and blood pressure.
A total of 690 people from a UK primary-care health centre were included in the study.
Each was randomly allocated to either the intervention group or to a control group.
In the intervention group, participants were encouraged to increase their fruit and vegetable consumption to at least 5 servings a day (1 portion being an 80 gram serving).
| Increased fruit and vegetable consumption reduces blood pressure.
Those in the control group were not instructed to alter their dietary habits.
Fruit and vegetable intake increased by 1.4 servings in the intervention group, compared with a very small (0.1 serving) increase in the control group.
Blood pressure decreased in the group with increased fruit and vegetable consumption, compared with the control group (systolic pressure decrease of 4 mm Hg, diastolic decrease of 1.5 mm Hg).
In addition, concentrations of a-carotene, b-carotene, lutein, b-cryptoxanthin, and ascorbic acid increased by more in the intervention group than in the control group.
There were no changes in either bodyweight or cholesterol concentrations between the two groups.
This suggested that the reduction in blood pressure was a result of the effect of increased fruit and vegetable intake.
Andrew Neil comments, "Our results accord with those of the DASH (Dietary Approaches to Stop Hypertension) trial, in which an increase in dietary fruit and vegetables for 8 weeks reduced systolic blood pressure by 2.8 mm Hg and diastolic pressure by 1.1 mm Hg more than a control diet.
"DASH differed fundamentally from our study in design, however, being a controlled feeding trial with meals prepared to a common protocol in research kitchens."
He concludes, "The falls in blood pressure in our study would be expected to produce small clinical effects, but would substantially reduce cardiovascular disease at the population level.
"A reduction of 2 mm Hg in diastolic blood pressure results in a decrease of about 17% in the incidence of high blood pressure, 6% in the risk of coronary heart disease, and 15% in the risk of stroke and transient ischemic attack."