Watermelon, Fruit for Cardiovascular Health
Watermelon is a fruit many people associate with hot summer days and picnics, but the sweet juices of this treat have some hidden health benefits as well. Researchers from two universities report that eating watermelon may support cardiovascular health by having a positive impact on several important factors.
Watermelon is more than a summer treat
Mice were the subjects in the new study conducted by experts from the University of Kentucky and Purdue University. Two groups of mice were fed a diet high in cholesterol and saturated fat, factors shown to contribute to cardiovascular disease.
One group of mice was then provided with water that contained 2% watermelon juice, while the other group of mice were given water mixed with a solution that matched the carbohydrate content of the watermelon juice. The investigators observed the following:
- Mice who drank the watermelon juice mixture had nearly 50 percent lower levels of bad cholesterol (LDL, low-density lipoprotein) than did the control mice
- Mice who consumed the watermelon juice also gained 30 percent less weight than did the control mice
- The accumulation of plaque in the arteries was 50 percent less in the mice that drank watermelon juice, and this group also had high citrulline levels
What is citrulline?
Citrulline is an amino acid that has the ability to relax blood vessels. This characteristic in turn improves blood flow. However, citrulline does not relax blood vessels directly.
Instead, when you ingest foods such as watermelon that contain citrulline, the body transforms it into another amino acid called arginine, and it is arginine that has a key role in relaxing blood vessels and improving blood flow.
According to Sibu Saha, one of the study's authors and professor of surgery at the University of Kentucky, "We know that watermelon is good for health because it contains citrulline." What remains for researchers to uncover, he noted, is how it works at the molecular level.
Other benefits of citrulline and watermelon
Citrulline has also demonstrated an ability to improve blood flow in another somewhat related study. In a 2011 issue of Urology, researchers reported on 24 men with mild erectile dysfunction. For one month, all the men took a placebo, followed by one month of taking 1.5 grams of citrulline daily.
When the men took the placebo, only two (8.3%) of the 24 men experienced an improvement in erection hardness scores from a "mild erectile dysfunction" score to a "normal erection function." However, when the men took citrulline, half of them (12) reported an improvement, and the mean number of intercourses per month also improved.
In a pilot study conducted at Florida State University, investigators found that citrulline helped lower blood pressure in people who were classified as prehypertensive (120-139 mmHg over 80-89 mmHg). About 60 percent of adults in the United States are prehypertensive or hypertensive, which is a risk factor for cardiovascular disease.
In the study, the nine adults in their fifties consumed 6 grams of citrulline/arginine from watermelon extract. The investigators reported that their findings were positive enough to warrant additional studies of watermelon and blood pressure.
Importance of watermelon
Currently, about 20 percent of watermelons crops are wasted for a variety of farmer and consumer reasons, but Shubin Saha, co-author and a Purdue Extension vegetable specialist, noted their findings may indicate a new use for these wasted fruits.
"We could use the wasted melons that can't go to market for extracting beneficial compounds," he explained. It should be noted that watermelon is also a good source of lycopene, an antioxidant also in tomatoes and that has been studied for a variety of benefits, including the fight against cardiovascular disease.
This latest study, and others, highlight the potential benefits of watermelon and citrulline. The citrulline in watermelon appears to provide cardiovascular benefits, including improved blood flow, reduction in plaque (a factor in atherosclerosis), weight loss, lower blood pressure, and reduced LDL cholesterol. Watermelon anyone?
Cormio L et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology 2011 Jan; 77(1): 119-22
Poduri A et al. Citrullus lanatus 'sentinel' (watermelon) extract reduces atherosclerosis in LDL receptor-deficient mice. Journal of Nutritional Biochemistry 2012. doi:10.1016/j.jnutbio.212.05.011