A new study suggests that the sweet summery treat, watermelon, might not just help you relax in the summer sun, but actually improve blood flow and lower blood pressure.

The latest superfood was tested in a study on nine subjects with prehypertension – a precursor to cardiovascular disease.

Assistant Professor Arturo Figueroa and Professor Bahram H. Arjmandi found that six weeks of daily doses of 6g of an amino acid extracted from watermelons, L-citrulline/L-arginine, showed improved arterial function and lowered aortic blood pressure in all nine subjects.

“We are the first to document improved aortic hemodynamics in prehypertensive, but otherwise healthy, middle-aged men and women receiving therapeutic doses of watermelon,” Figueroa said.

“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,” he said.

“Watermelon is the richest edible natural source of L-citrulline, which is closely related to L-arginine, the amino acid required for the formation of nitric oxide essential to the regulation of vascular tone and healthy blood pressure,” Figueroa said.

Once in the body, the L-citrulline is converted into L-arginine. Simply consuming L-arginine as a dietary supplement isn’t an option for many hypertensive adults, said Figueroa, because it can cause nausea, gastrointestinal tract discomfort, and diarrhea.

In contrast, watermelon is well tolerated. Participants in the Florida State pilot study reported no adverse effects.

In addition to the vascular benefits of citrulline, watermelon provides abundant vitamin A, B6, C, fiber, potassium and lycopene, a powerful antioxidant. Watermelon may even help to reduce serum glucose levels, according to Arjmandi.

“Cardiovascular disease (CVD) continues to be the leading cause of death in the United States,” Arjmandi said. “Generally, Americans have been more concerned about their blood cholesterol levels and dietary cholesterol intakes rather than their overall cardiovascular health risk factors leading to CVD, such as obesity and vascular dysfunction characterized by arterial stiffening and thickness –– issues that functional foods such as watermelon can help to mitigate.

“By functional foods,” said Arjmandi, “we mean those foods scientifically shown to have health-promoting or disease-preventing properties, above and beyond the other intrinsically healthy nutrients they also supply.”

Figueroa said oral L-citrulline supplementation might allow sufferers to cut down on  antihypertensive drugs necessary to control blood pressure.

“Even better, it may prevent the progression from prehypertension to hypertension in the first place,” he said.

Findings from the pilot study at Florida State are described in the American Journal of Hypertension.

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