Improvement of vascular endothelial function by intake of lycopene-rich tomato juice in healthy adults: a randomized, placebo-controlled, double-blind, parallel-group comparative study

Abstract

Maintaining normal vascular endothelial function is important for preventing arteriosclerosis. Flow-mediated dilatation (FMD) is widely used to evaluate vascular endothelial function. Lycopene, a carotenoid abundant in tomatoes, has been reported to improve FMD, but its effect after 4 weeks of intake remains unclear. We conducted a randomized, placebo-controlled, double-blind, parallel-group trial to assess the effects of lycopene. Seventy-five healthy adults with borderline FMD (4–7%) were randomly assigned to placebo juice (0.7 mg lycopene), tomato juice (TJ, 15.0 mg), or high-lycopene tomato juice (HLTJ, 26.7 mg) groups. FMD, serum lycopene, oxidative stress markers (malondialdehyde, 8-hydroxy-2′-deoxyguanosine, 8-iso-prostaglandin F2α), and nitrogen oxide concentrations were measured every 4 weeks over a 12-week intervention. The participants analyzed included 23 (placebo), 25 (TJ), and 24 (HLTJ). Data were analyzed using a linear mixed effects model adjusting for baseline covariates and a post hoc Dunnett's test with Bonferroni correction for intergroup comparisons. At week 12, FMD was significantly higher in the TJ (6.1 ± 0.5%, p < 0.001) and HLTJ groups (7.0 ± 0.7%, p < 0.001) than in the placebo group (5.4 ± 0.6%). In the HLTJ group, FMD at weeks 4 (6.2 ± 1.0%, p < 0.001) and 8 (6.7 ± 0.7%, p < 0.001) was significantly higher than in the placebo group (5.4 ± 0.9% and 5.3 ± 0.6%, respectively). Serum lycopene concentrations were significantly increased in TJ and HLTJ groups than in the placebo group. No significant differences were observed in oxidative stress or nitrogen oxide levels. These findings suggest that lycopene intake improves vascular endothelial function, though the mechanism remains unclear. Trial registration: UMIN000051176.