Scientists who carried out studies on mice fed a high-fat diet found the fruit halved the rate at which `bad` low-density lipoprotein, or LDL, accumulated, Daily Mail reported.
LDL is a form of cholesterol that leads to clogged arteries and heart disease.
The researchers from Purdue University, US, also observed that eating watermelon regularly helped to control weight gain and resulted in fewer fatty deposits inside blood vessels.
They believe the secret to watermelon`s health-boosting properties lies in citrulline, a chemical found in the juice.
Although the latest investigation showed no significant effects on blood pressure, it did reveal watermelons had a powerful impact on other heart risk factors.
In Britain around 270,000 people a year suffer heart attack and nearly one in three die before they could reach hospital.