FRIDAY, Jan. 17, 2020 (American Heart Association News) -- Grapefruit looks sweet and friendly, but you might have heard it possesses powers far beyond those of ordinary produce. Some of that reputation is fact, and some is myth. Facts first: According to the U.S. Department of Agriculture, half a medium grapefruit has only 41 calories and nearly half a day's recommended supply of vitamin C. "In addition, it's a reasonable source of potassium," which is important for maintaining healthy blood pressure, said Karen Collins, a registered dietitian in western New York who specializes in cancer prevention and heart health. Grapefruit also is laden with natural plant compounds called phytochemicals, specifically flavonoids, which studies show can help fight stroke and heart disease....