The extract, a rich source of the amino acids l-citrulline and l-arginine, was associated with reductions in systolic and diastolic blood pressure in the arm of 15.1 and 7.6 mmHg, respectively, according to results published in the American Journal of Hypertension.
Researchers from Florida State University also report similar reductions in blood pressure measured in the ankle, but no changes were recorded in heart rate.
Led by Arturo Figuero, the researchers note that the potential blood pressure lowering effects of l-citrulline and l-arginine has previously been demonstrated in adults with prehypertension and hypertension. An earlier study from the same group with 4 grams per day of the watermelon extract only reduced systolic blood pressure, however.
The new study used a dose of 6 grams per day and the benefits to both systolic and diastolic blood pressure may be dose-dependent, they said.
High blood pressure (hypertension),defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, is a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
Figuero and his co-workers recruited 14 adults with prehypertension or stage 1 hypertension and with an average age of 58 to participate in their clinical trial. Participants were assigned to receive the watermelon extract (provided by Milne Fruit Products and providing a daily dose of l-citrulline/l-arginine of 6 g) or placebo for six weeks. After this period, they underwent a two-week washout period before crossing over to the other intervention group.
At the end of the study, results showed that systolic blood pressure in the arm and ankle decreased by an average of 15.1 and 11.5 mmHg in the watermelon group, compared to placebo, while diastolic blood pressure at the same sites decreased by 7.6 and 7.8 mmHg, respectively.
“Interestingly, watermelon extract reduced ankle systolic blood pressure from above 175 mm Hg to below this cut-point in 50% of the subjects,” wrote the researchers.
“An ankle systolic blood pressure greater than 175 mm Hg is associated with prehypertension and hypertension and subclinical arterial damage in overweight/obese adults. A normal ankle systolic blood pressure is clinical important as cardiovascular events were lower by about two-fold in those with normal ankle systolic blood pressure than in those with high ankle systolic blood pressure during a 15-year follow-up.”
Source: American Journal of Hypertension
Volume 25, Number 6, Pages 640-643, doi: 10.1038/ajh.2012.20
“Watermelon Extract Supplementation Reduces Ankle Blood Pressure and Carotid Augmentation Index in Obese Adults With Prehypertension or Hypertension”
Authors: A. Figueroa, M.A. Sanchez-Gonzalez, A. Wong, B.H. Arjmandi