The associations between oxygen radical absorbance capacity of dietary intake and hypertension in type 2 diabetic patients

The objective of this study was to investigate the potential associations between oxygen radical absorbance capacity (ORAC) of fruits, vegetables, legumes and nuts, and blood pressure in type 2 diabetic patients in Tehran. In a cross-sectional study of 506 type 2 diabetic patients, aged 28-75 years, usual dietary intakes were assessed by means of a 168-item food-frequency questionnaire. To calculate the estimated hydrophilic-ORAC, total ORAC, and total phenolics (TP) of fruits, vegetables, legumes and nuts for each participant, we used the United States Department of Agriculture Database for ORAC. We examined the associations between total ORAC and TP scores, and hypertension using logistic regression. After adjustment for potential confounders, a higher total ORAC score was associated with lower risk of hypertension. The odds ratios (ORs) of systolic blood pressure (SBP) >140 mm Hg across increasing quartiles of the total ORAC score were 1.0, 0.71, 0.38 and 0.56 (P for trend=0.016). The ORs of diastolic blood pressure (DBP) >90 mm Hg across increasing quartiles of the total ORAC score were 1.0, 0.59, 0.47 and 0.35 (P for trend=0.008). Further adjustment for energy, protein and sodium intakes slightly strengthened these associations. Multivariate ORs of elevated SBP across quartiles of TP score were 1.0, 0.83, 0.41 and 0.63 (P for trend=0.027), and for elevated DBP were 1.0, 0.50, 0.40 and 0.38 (P for trend=0.006). Further adjustment for energy, protein and sodium intakes did not change the results materially. Our findings suggest that total antioxidant capacity of the dietary intake was negatively associated with hypertension in type 2 diabetic patients.