The effect of raisins on biomarkers of endothelial function and oxidant damage; an open-label and randomized controlled intervention

Based on the existing data in grapes and wine, the aim of the present study was to investigate the probability that raisins improve clinical features and markers of oxidative stress, inflammation and arterial function in healthy smokers. Thirty-six apparently healthy smokers were recruited to an open-label and randomized, controlled, 4 week prospective intervention. All participants were reported to consume less than the recommended amount of five servings fruits and vegetables daily. Participants in the intervention were instructed to consume raisins equal to five fruit servings (90 g/d). Anthropometric and blood pressure (BP) measurements, assessment of dietary intake, and fasting blood draws were conducted at baseline and at week 4. Biochemical (glucose, lipids, liver enzymes), inflammation [C-reactive protein (CRP), leptin], oxidative stress [Malondialdehyde (MDA), Advanced oxidation protein products (AOPPs)] and arterial function markers [Flow-mediated dilatation (FMD), Pulse wave velocity (PWV), Intercellular adhesion molecule-1 (ICAM-1), Nitric oxide (NO)] were assessed pre and post-intervention. Baseline characteristics did not differ between the intervention and control arm. No effect of daily raisin consumption was observed on markers assessed between baseline and week 4 in either arm. Regarding vegetable consumption, no difference was observed in either group between baseline and post-intervention; however, as expected, a significant increase was reported in the intervention arm in fruit consumption between baseline and end point (p < 0.001) and between two arms post-intervention (p < 0.001). When analyzing according to age, ICAM-1 levels significantly decreased in subjects > 30 years (n = 8) in intervention arm (390.1 +/- 17.6 to 302.2 +/- 11 ng/mL, p = 0.004). After analysis of the data for sex, women in intervention (n = 5) decreased significantly diastolic BP (74.6 +/- 4.2 to 67.4 +/- 2.6 mg/dL, p = 0.043), total cholesterol (175.8 +/- 7 to 166.6 +/- 6.6 mg/dL, p < 0.001) and LDL-cholesterol (96.2 +/- 9.6 to 89 +/- 10.5 mg/dL, p = 0.012). However, due to the small sample size in the above, no safe conclusions can be exported.