Wolfberry Consumption with a Healthy Dietary Pattern Lowers Oxidative Stress and Improves Carotenoids Status in Middle-Aged and Older Adults: A Randomized Controlled Trial

Abstract

Abstract Objectives The incorporation of zeaxanthin rich wolfberry (Lycium barbarum) into a healthy dietary pattern may augment its antioxidant effects although evidence evaluating whole fruits is lacking. The objectives of this study are to (1) investigate the impact of dietary counselling, either with or without whole dried wolfberry on oxidative stress status in middle-aged and older Singaporean adults and (2) delineate underlying mechanisms by examining associations with the corresponding changes in carotenoids status. Methods In this 16-week, parallel design randomized controlled trial, 40 subjects (29 F, 11 M; aged 50 to 64 y) received dietary counselling to follow a healthy dietary pattern. Compared to the control group (CG, n = 18), the wolfberry group (WG, n = 22) additionally cooked and consumed 15 g/d whole dried wolfberry with their main meals. Biomarkers of oxidative stress (plasma malondialdehyde (MDA) by thiobarbituric acid reactive substance assay and 8-isoprostanes by ELISA) were measured at baseline and week 16. Plasma and dietary carotenoids analyzed by HPLC and 3-day food records respectively were measured at baseline, week 8 and week 16 while skin carotenoids status (SCS) by resonance Raman spectroscopy was assayed every 4 weeks. Results Plasma 8-isoprostanes showed a time effect (P < 0.05), attributed to the marked decline in the WG only (WG: −19.0 ± 43.6 ng/L; CG: −7.7 ± 38.7 ng/L, mean ± SD) though no effect was observed for MDA. A significant interaction effect (P < 0.001), driven by higher plasma zeaxanthin (WG: +0.08 ± 0.13 nmol/L; CG: −0.03 ± 0.05 nmol/L) and SCS (WG: +4242 ± 4938 a.u.; CG: +1713 ± 5921 a.u.) was observed in the WG with a marked increase evident from week 8 onwards although concentrations of the other plasma carotenoids were maintained. Moreover, the change value for plasma zeaxanthin in the WG was inversely associated with the corresponding changes in plasma 8-isoprostanes (−0.21 (−0.43, 0.00) ng/µmol, regression coefficient (95% CI); P = 0.05). This same association was absent in the CG. Conclusions Consuming wolfberry with a healthy dietary pattern attenuates oxidative stress in middle-aged and older adults and this may be attributed to the rich zeaxanthin content in wolfberry. Funding Sources National University of Singapore Ministry of Education, Singapore Agency for Science, Technology and Research.