ArticlesEffects of fruit and vegetable consumption on plasma antioxidant concentrations and blood pressure: a randomised controlled trial
Introduction
Ecological and epidemiological evidence suggest that high consumption of fruit and vegetables is associated with a reduced risk of cancer1 and cardiovascular disease.2 Several mechanisms have been proposed for this process, including an increased nutrient intake of antioxidant compounds. However, intervention trials of vitamin supplements to increase circulating plasma concentrations of antioxidant vitamins have produced little evidence to support this hypothesis.3, 4, 5, 6 The health benefits of eating fruit and vegetables may be due, in part, to mechanisms other than their antioxidant vitamin content such as blood pressure lowering.7 Current evidence, including unpublished trial data (http://www.hpsinfo.org), therefore points to the beneficial effects of eating more fruit and vegetables rather than vitamin supplementation.
An average daily intake of at least five portions of fruit and vegetables is recommended in the UK,8 which would represent an increase in consumption of 50%9 with only about 40% of men and women currently achieving this target.10 Although short-term intensive dietary interventions in highly selected populations increase fruit and vegetable intake substantially,11, 12 raise plasma antioxidant concentrations,12 and lower blood pressure,7 whether such interventions are feasible in the general population is uncertain. We did a randomised, controlled trial to investigate the effect of a 6-month primary-care intervention to increase fruit and vegetable consumption in a healthy general population with a wide range of eating habits.
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Participants
We identified all patients aged 25–64 years without serious chronic illness from the lists of two general practices based in a health centre in Thame, Oxfordshire, UK. The general practices had few patients from ethnic minorities. We excluded patients with cardiovascular diseases (other than hypertension), gastrointestinal disease, cancer, serious psychiatric disorders, or hypercholesterolaemia; patients who had undergone a recent traumatic event, such as bereavement; and those unable to give
Participants
1045 (45%) of 2302 eligible mailed patients responded to the initial invitation (figure). Respondents were older than non-respondents (mean [SD] age 46·1 [10·1] years vs 40·1 [10·3] years; difference 6·0 years, 95% CI 5·2–6·9) and a higher proportion were women (55% vs 48%; difference 7%, 2·9–11·1). Respondents were less materially deprived than non-respondents (mean Townsend material deprivation score19 −0·98 (1·35) vs −0·75 (1·38); difference −0·23, −0·34 to −0·12). 316 respondents (207 women
Discussion
Our results show that a primary-care intervention can increase self-reported fruit and vegetable intake; raise plasma concentrations of α-carotene, β-carotene, lycopene, β-cryptoxanthin, and ascorbic acid; and result in significant decreases in systolic and diastolic blood pressure.
Our analysis included all possible randomised patients irrespective of complete data or compliance. The study population was demographically heterogeneous with men and women aged 25–64 years being eligible for
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