Randomised controlled trial of effect of fruit and vegetable consumption on plasma concentrations of lipids and antioxidants

Abstract

Objectives: To determine the extent to which plasma antioxidant concentrations in people with habitual low intake of fruit and vegetables respond to increased intakes of these foods. To examine whether advice to increase fruit and vegetables will result in reduction of concentrations of total and low density lipoprotein cholesterol.

Design: Randomised controlled trial in which intervention and control groups were followed up for eight weeks. The intervention group was asked to consume eight servings of fruit and vegetables a day.

Setting: Dunedin, New Zealand.

Subjects: Eighty seven subjects with normal lipid concentrations who ate three or fewer servings of fruit and vegetables daily.

Main outcome measures: Plasma concentrations of vitamin C, retinol, alpha and beta carotene, alpha tocopherol, lipids, and lipoproteins. Dietary intake assessed with diet records over four days.

Results: The mean plasma vitamin C, alpha carotene, and beta carotene concentrations increased in parallel with increased dietary intake of fruit and vegetables in the intervention group. Concentrations of retinol, alpha tocopherol, lipids, and lipoproteins remained unchanged despite some increase in dietary vitamin E and a small reduction in saturated fat intake.

Conclusions: Following a recommendation to increase fruit and vegetable consumption produces change in plasma concentrations of vitamin C, alpha carotene, and beta carotene likely to reduce incidence of cancer. More specific dietary advice to modify fat intake may be necessary to reduce the risk of cardiovascular disease mediated by lipoprotein and vitamin E.