Dealing with High-blood Pressure? Eat More Melons
Nutrition experts at UT Southwestern Medical Center say there’s no better way to lower your blood pressure than by indulging in some of the season’s potassium-rich fruit and vegetables.
“Melons like cantaloupe and watermelon are particularly high in potassium,” says Lona Sandon, assistant professor of clinical nutrition at UT Southwestern and spokesperson for the American Dietetic Association. “One fourth a cantaloupe contains 800 to 900 milligrams of potassium, roughly 20 percent of the recommended daily value.”
Two cups of watermelon contains nearly 10 percent of the daily recommended value.
Ms. Sandon said that dried apricots, avocados, figs, kiwi, oranges, raisins, dates, beans, potatoes, tomatoes and even grapefruit are other good sources of potassium.
The U.S. Department of Agriculture recommends that most adults get 4,044 milligrams of potassium from food and beverages each day.
Watermelon Can Improve Heart Health While Controlling Weight Gain
According to research from Purdue University and University of Kentucky, mice that were given a diet which included watermelon juice received considerable benefits when compared to the control group.
The experts suggest, in the Journal of Nutritional Biochemistry, that citrulline, a compound found in watermelon, was responsible for the mice's lower cholesterol, weight, and arterial plaque.
This study coincides with prior research, also by the University of Kentucky, which found that watermelon consumption caused a reduction in atherosclerosis in animals.
Since other research has demonstrated that consuming this type of fruit can lower blood pressure, explained Shubin Saha, co-author and a Purdue Extension vegetable specialist, they were interested to examine what it could do in this research.
"We didn't see a lowering of blood pressure, but these other changes are promising," Shubin Saha added.
The scientists divided mice into two groups for their investigation, both were given diets high in saturated fat and cholesterol. One group drank water that consisted of 2% watermelon juice, while the other mice drank the exact amount of water mixed with a solution that matched the carbohydrate content of the fruit juice.
Results showed that nearly 50% less LDL cholesterol, or the "bad" cholesterol, was found in the animals who drank the watermelon juice, who also gained 30% less weight than the control group.
A 50% decrease in plaque in the arteries, as well as high citrulline levels, were found in the experimental group.
"We know that watermelon is good for health because it contains citrulline," revealed Sibu Saha, a professor of surgery at the University of Kentucky. "We don't know yet at what molecular level it's working, and that's the next step."
The team hopes to discover a secondary market for watermelons in nutraceuticals, which are food or food components that provide health and medical benefits, such as preventing and treating certain diseases.
Approximately 20% of watermelon crop goes to waste each year, according to Shubin Saha. It may be because buyers think the fruit does not look appealing or because some farmers do not think it is worth spending that much money on harvesting it, as prices drop during the peak of watermelon season.
Shubin Saha explained: "We could use the wasted melons that can't go to market for extracting beneficial compounds. Growers are putting energy into these crops, so if we can do something to help them market their additional product, that would be a benefit to the industry and consumers."
Watermelon reduces atherosclerosis
In a recent study by University of Kentucky researchers, watermelon was shown to reduce atherosclerosis in animals.
The animal model used for the study involved mice with diet-induced high cholesterol. A control group was given water to drink, while the experimental group was given watermelon juice. By week eight of the study, the animals given watermelon juice had lower body weight than the control group, due to decrease of fat mass. They experienced no decrease in lean mass. Plasma cholesterol concentrations were significantly lower in the experimental group, with modestly reduced intermediate and low-density lipoprotein cholesterol concentrations as compared to the control group.
A measurement of atherosclerotic lesion areas revealed that the watermelon juice group also experienced statistically significant reductions in atherosclerotic lesions, as compared to the control group.
"Melons have many health benefits," said lead investigator Dr. Sibu Saha. "This pilot study has found three interesting health benefits in mouse model of atherosclerosis. Our ultimate goal is to identify bioactive compounds that would improve human health."
Watermelon lowers blood pressure
No matter how you slice it, watermelon has a lot going for it –– sweet, low calorie, high fiber, nutrient rich –– and now, there's more. Evidence from a pilot study led by food scientists at The Florida State University suggests that watermelon can be an effective natural weapon against prehypertension, a precursor to cardiovascular disease.
It is the first investigation of its kind in humans. FSU Assistant Professor Arturo Figueroa and Professor Bahram H. Arjmandi found that when six grams of the amino acid L-citrulline/L-arginine from watermelon extract was administered daily for six weeks, there was improved arterial function and consequently lowered aortic blood pressure in all nine of their prehypertensive subjects (four men and five postmenopausal women, ages 51-57).
"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.
"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," 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. And, 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 a reduced dosage of antihypertensive drugs necessary to control blood pressure.
"Even better, it may prevent the progression from prehypertension to hypertension in the first place," he said.
While watermelon or watermelon extract is the best natural source for L-citrulline, it is also available in the synthetic form in pills, which Figueroa used in a previous study of younger, male subjects. That investigation showed that four weeks of L-citrulline slowed or weakened the increase in aortic blood pressure in response to cold exposure. It was an important finding, said Figueroa, since there is a greater occurrence of myocardial infarction associated with hypertension during the cold winter months.
"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," Figueroa said. "The optimal dose appears to be four to six grams a day."
Approximately 60 percent of U.S. adults are prehypertensive or hypertensive. Prehypertension is characterized by systolic blood pressure readings of 120-139 millimeters of mercury (mm Hg) over diastolic pressure of 80-89 mm Hg. "Systolic" refers to the blood pressure when the heart is contracting. "Diastolic" reflects the blood pressure when the heart is in a period of relaxation and expansion.
Findings from Figueroa's latest pilot study at Florida State are described in the American Journal of Hypertension. A copy of the paper ("Effects of Watermelon Supplementation on Aortic Blood Pressure and Wave Reflection in Individuals With Prehypertension: A Pilot Study") can be accessed online.
The paper's lead author, Figueroa holds a medical degree, a doctoral degree in physiological sciences, and a master's degree in sports medicine. He has been a faculty member in the Florida State University Department of Nutrition, Food and Exercise Sciences since 2004. Figueroa's coauthor and colleague Arjmandi serves as chairman of the department, which is a part of Florida State's interdisciplinary College of Human Sciences. Arjmandi also is the author or coauthor of an extensive body of published research on the health benefits of prunes and other functional foods.