The research, led by food scientists at The Florida State University suggests that 6 weeks of L-citrulline extract from watermelon, reduced blood pressure and aortic wave reflection in middle aged individuals with pre-hypertension.
"We are the first to document improved aortic hemodynamics in pre-hypertensive but otherwise healthy middle-aged men and women receiving therapeutic doses of watermelon," said Dr. Arturo Figueroa, lead researcher of the new study.
"These findings suggest that this 'functional food' has a vasodilatory effect, and one that may prevent prehypertension from progressing to full-blown hypertension, a major risk factor for heart attacks and strokes,” added Figueroa
Pre-hypertension is classified as a blood pressure between 120/80 mmHg and 139/89 mmHg. It is a precursor of hypertension, and a risk factor for cardiovascular disease.
L-arginine is important in the formation of nitric oxide, a regulator of blood pressure through its effects on widening blood vessels. However, supplementation of L-arginine is not recommended for many people, as it can lead to nausea, gut discomfort, and diarrhoea.
"Watermelon is the richest edible natural source of L-citrulline, which is closely related to L-arginine," said Dr. Figueroa.
Once ingested, L-citrulline from watermelon is converted into L-arginine without causing the problems associated with consumption of L-arginine.
There is evidence that oral L-citrulline and watermelon supplementation can reduce peripheral blood pressure and improve nitric oxide dependent vasodilation in hypertensive and diabetic rats. In addition L-arginine has been shown to decrease brachial blood pressure through improved endothelial nitric oxide production.
However, aortic blood pressure and pulse wave reflection are more reliable markers of cardiovascular risk than brachial blood pressure, and so the new study investigated the effects of watermelon supplementation on these biomarkers in a small population of middle-aged individuals with pre-hypertension.
Dr. Figueroa and colleagues found supplementation with six grams of L-citrulline from watermelon, resulted in improved arterial function, and lowered aortic blood pressure in all nine pre-hypertensive subjects.
The supplementation significantly decreased the second systolic peak, which is associated with reductions in pulse wave reflections, but had no significant effect on the first – which is mainly determined by other factors like stroke volume.
Watermelon supplementation did not alter heart rate, reflection time, or aortic pulse wave velocity.
The researchers concluded that six weeks of watermelon supplementation improved aortic hemodynamics in middle-aged adults with pre-hypertension.
L-citrulline supplementation [from watermelon] could lead to reduced doses of antihypertensive drugs being needed to control blood pressure, or could even prevent progression from pre-hypertension to hypertension in the first place, said Figueroa.
"Individuals with increased blood pressure and arterial stiffness –– especially those who are older and those with chronic diseases such as type 2 diabetes –– would benefit from L-citrulline in either the synthetic or natural (watermelon) form," he added
"Given the encouraging evidence generated by this preliminary study, we hope to continue the research and include a much larger group of participants in the next round," said Figueroa.
Source: American Journal of Hypertension
Published online ahead of print, doi: 10.1038/ajh.2010.142
“Effects of Watermelon Supplementation on Aortic Blood Pressure and Wave Reflection in Individuals With Prehypertension: A Pilot Study”
Authors: A. Figueroa, M.A. Sanchez-Gonzalez, P.M. Perkins-Veazie, B.H. Arjmandi