ORIGINAL ARTICLE Fruit and vegetable intake and the association with glucose parameters: a cross-sectional analysis of the Let’s Prevent Diabetes Study P Carter 1 , LJ Gray 2 , D Talbot 3 , DH Morris 1 , K Khunti 2 and MJ Davies 1 BACKGROUND: Dietary recommendations for the prevention of type 2 diabetes mellitus include the message to consume 400 g fruit and vegetables per day. Measurement of habitual diet is inherently difficult, yet errors due to self-report can be eliminated by the use of nutritional biomarkers. The aim of this study was to determine plasma vitamin C concentrations as a biomarker for fruit and vegetable intake in individuals identified at high risk of diabetes. Fruit and vegetables may confer benefit via their antioxidant capacity, thus we also measured urinary F 2 -isoprostanes as a marker for oxidative stress. SUBJECTS/METHODS: Participants recruited from a high-risk population as part of a diabetes prevention trial provided fasting blood samples and a spot urine sample for the quantification of plasma vitamin C and F 2 -isoprostanes, respectively. We compared glycaemic parameters by the increments of the standard deviation of plasma vitamin C using multiple regression models. RESULTS: Mean plasma vitamin C of participants was 39.3 mmol/l (s.d. 21.8). In the unadjusted model, 1 s.d. plasma vitamin C was significantly and inversely associated with HbA1c, fasting and 2 h blood glucose (Pp0.0001). Relationships remained significant after adjustment for demographic variables and confounding factors. No significant association was observed between plasma vitamin C and urinary F 2 -isoprostanes. CONCLUSION: The data adds to the evidence that small lifestyle changes may influence glucose regulation. The role that fruit and vegetables independently have should be investigated further. European Journal of Clinical Nutrition (2013) 67, 12–17; doi:10.1038/ejcn.2012.174; published online 7 November 2012 Keywords: type 2 diabetes; glucose; fruit; vegetables; vitamin C; nutrition therapy INTRODUCTION Consumption of five portions of fruit and vegetables per day (400 g/day) is widely recommended as part of a healthy balanced diet. 1 This has been incorporated into health messages following a plethora of epidemiological data on the associations between greater fruit and vegetable intake and reduced risk of cardiovascular disease and cancer. 2–4 It has been estimated that up to 2.7 million lives worldwide could be saved with sufficient fruit and vegetable consumption. 5 The prevalence of type 2 diabetes mellitus (T2DM) is estimated to be 8.3% worldwide. 6 Lifestyle modification programmes can prevent T2DM, and dietary changes alone can significantly reduce the risk of developing diabetes. 7 Current dietary guidelines for the prevention of T2DM also include the message to consume at least 400 g fruit and vegetables per day. 8–10 However, a recent meta- analysis found significant benefits for greater consumption of green leafy vegetables for the prevention of T2DM but not for greater consumption of fruit and vegetables in general. 11 The meta-analysis was based on observational studies, which may have been unable to identify small differences in diet as assessed by food frequency questionnaires. Accurate measurement of diet is a difficult area of research; 12 however, errors due to self-report can be eliminated using nutritional biomarkers. 13 Plasma vitamin C consistently demonstrates a high correlation to fruit and vegetable intake, 14,15 and dietary vitamin C is the strongest predictor of plasma vitamin C, with around 90% of dietary vitamin C being obtained from fruit and vegetable consumption. 16 Fruits and vegetables supply antioxidants, which may counter- act harmful effects of reactive oxygen species implicated in the development and progression of T2DM. 17 Lipid peroxidation is a central feature of oxidative stress; measurement of F 2 -isoprostanes in body fluids provides a reliable, non-invasive approach to assess lipid peroxidation more accurately than other methods. 18,19 OBJECTIVE The aim of this study was to estimate fruit and vegetable consumption using plasma vitamin C as a biomarker of intake in a large multi-ethnic population, to determine independent associations between fruit and vegetable intake and glycaemic parameters and to assess levels of oxidative stress by measure- ment of F 2 -isoprostanes in urine. METHODS Participants Participants were recruited as part of the screening phase of a large community intervention trial for the prevention of T2DM, Let’s Prevent Diabetes, as described in detail elsewhere. 20 Recruited general practices from Leicestershire (UK) used a validated computerized risk score to identify individuals at high risk of T2DM. 21 Individuals ranked in the top 1 Department of Cardiovascular Sciences, University of Leicester, Leicester Diabetes Centre, Leicester, UK; 2 Department of Health Sciences, University of Leicester, Leicester Diabetes Centre, Leicester, UK and 3 Unilever Discover, Colworth Science Park, Sharnbrook, Bedford, UK. Correspondence: Dr P Carter, Leicester Diabetes Centre – Air, Leicester General Hospital, Leicester LE5 4PW, UK. E-mail: Pc154@le.ac.uk Received 20 July 2012; revised 1 October 2012; accepted 4 October 2012; published online 7 November 2012 European Journal of Clinical Nutrition (2013) 67, 12–17 & 2013 Macmillan Publishers Limited All rights reserved 0954-3007/13 www.nature.com/ejcn