Watermelon Extract Supplementation Reduces Ankle Blood Pressure and Carotid Augmentation Index in Obese Adults With Prehypertension or Hypertension

BACKGROUND Ankle-brachial index (ABI) and ankle blood pressure (BP) are associated with increased carotid wave reflection (augmentation index, AIx). Oral l-citrulline and l-arginine from synthetic or watermelon sources have reduced brachial BP, aortic BP, and aortic AIx. A directly measured carotid AIx (cAIx) rather than aortic AIx has been proposed as a better measurement of central AIx. We evaluated the effects of watermelon extract on ankle BP and cAIx in individuals with normal ABI and prehypertension or stage 1 hypertension. METHODS Ankle and brachial systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), cAIx, ABI, and heart rate (HR) were evaluated in the supine position in 14 adults (11 women/3 men, age 58 +/- 1 years) with prehypertension or stage 1 hypertension (153 +/- 4 mm Hg). Subjects were randomly assigned to 6 weeks of watermelon extract supplementation (L-citrulline/L-arginine, 6 g daily) or placebo followed by a 2-week washout period and then crossover. RESULTS Ankle and brachial SBP (-11.5 +/- 3.8 and -15.1 +/- 2.8 mm Hg), DBP (-7.8 +/- 2.3 and -7.6 +/- 1.8 mm Hg), and MAP (-9.8 +/- 2.6 and -7.3 +/- 1.8 mm Hg), and cAIx (-8.8 +/- 2.6 %) decreased significantly (P < 0.05) after watermelon supplementation compared to placebo. Watermelon supplementation had no significant effect (P > 0.05) on ABI and HR. CONCLUSIONS This study shows that watermelon extract supplementation reduces ankle BP, brachial BP, and carotid wave reflection in obese middle-aged adults with prehypertension or stage 1 hypertension and normal ABI, which may reflect improved arterial function.