Daily 100% watermelon juice consumption and vascular function among postmenopausal women: A randomized controlled trial.

BACKGROUND AND AIMS: Watermelon juice is a rich food source of cardioprotective compounds such as arginine, citrulline, and lycopene. Preventative interventions are warranted as risk of cardiovascular disease increases among women after menopause, and age alone is an independent risk factor for vascular dysfunction. Thus, this study evaluated the effects of 100% watermelon juice on measures of vascular function. METHODS AND RESULTS: In this randomized, double-blind, placebo-controlled, crossover trial, 21 healthy postmenopausal women were randomized to consume two 360 mL servings of 100% watermelon juice per day or an isocaloric placebo for four weeks. Following a two-week washout period, they consumed the other beverage for an additional four weeks. Before and after each treatment arm, a fasting blood sample was taken for measurement of serum arginine, citrulline, lycopene, glucose, and insulin. Assessments of vascular function included pulse pressure, pulse wave velocity, 24-h ambulatory blood pressure, and flow-mediated dilation. General linear mixed models with intent-to-treat analyses were used to examine the effects of the intervention. Despite a significant treatment effect for circulating lycopene (p = 0.002), no changes in arginine, citrulline, or any vascular measures were observed. Although the juice intervention resulted in a slight but significant increase in fasting serum glucose (p = 0.001), changes in glucose homeostasis were not clinically significant. CONCLUSION: In contrast to findings from previous studies in younger adults and those with pre-existing hypertension, measures of vascular function in this cohort of healthy postmenopausal women were not impacted by supplemental watermelon juice. CLINICALTRIALS. GOV IDENTIFIER: NCT03626168.

Variation of Serum Lycopene in Response to 100% Watermelon Juice: An Exploratory Analysis of Genetic Variants in a Randomized Controlled Crossover Study.

BACKGROUND: Watermelon, a rich source of lycopene, has garnered attention for cardioprotective effects including cholesterol reduction and promotion of redox balance. It is unknown whether 100% watermelon juice may represent a food-first approach to confer cardioprotective benefits of lycopene. OBJECTIVES: This study examined influences of 100% watermelon juice on serum lycopene, lipids, and antioxidant capacity. Secondly, the study explored genetic influences on lycopene metabolism and bioavailability. METHODS: A placebo-controlled, randomized, double-blind, crossover trial with postmenopausal women (n = 16, mean ± SD age: 60 ± 4.1 y) assessed effects of 100% watermelon juice on mechanistic and clinical outcomes influencing vascular function. Participants maintained low-lycopene diets for a 1-wk run-in period and throughout the study. Morning and evening consumption of 100% watermelon juice provided a daily dose of 14.4 ± 0.34 mg lycopene. Study arms of 4 wk were separated by a 2-wk washout period. Saliva was collected for genetic analysis of single nucleotide polymorphisms, and fasting blood samples were taken pre- and post-study arms. Statistical analyses included mixed models, linear regression, and nonparametric tests. RESULTS: Serum lycopene exhibited a significant treatment effect (P = 0.002) along with notable interindividual responses; however, significant improvements in serum lipids or antioxidant capacity were not observed. Genetic variant rs6564851 in the ß-carotene 15,15'-oxygenase-1 (BCO1) gene was associated with changes in lycopene such that TT homozygotes exhibited a significantly greater increase (ß ± SE: 13.4 ± 1.6, P = 1.4 × 10-06). CONCLUSIONS: Watermelon juice supplementation did not result in improvements in serum lipids or antioxidant capacity; however, results support findings in which watermelon juice significantly, yet differentially, increased circulating lycopene. Genetics appears to explain some of the variability. Given that dose has been shown to overcome individual responsiveness to lycopene interventions, future investigations with varying doses of lycopene-rich foods would be strengthened by genotyping so as to establish personalized nutrition recommendations.This trial was registered at clinicaltrials.gov as NCT03626168.