Heart health: Regular watermelon consumption may have benefits

Jun 02, 2023

Watermelons contain many nutrients, such as potassium, vitamin C, and magnesium. The fruit also has a high bioavailability of antioxidants, including lycopene and l-citrulline.

Studies have shown that watermelon supplements and extracts decrease blood pressure and cholesterol levels.

Comparably fewer studies investigate raw watermelon, however, and those that do tend to involve large quantities of over 2 lbs per day.

Nevertheless, these studies also report that consumption of the fruit is linked to lower cholesterol and body weight, as well as a lower risk of prostate, lung, and breast cancer.

Further study of raw watermelon’s health effects could improve dietary guidelines and prevention strategies for cardiometabolic health.

Recently, two studies that investigated the health effects of watermelon consumption.

The first study, published in Nutrients, found that children and adults who consumed watermelon had a higher intake of various nutrients, including dietary fiber, magnesium, and potassium, than non-consumers. They also had a lower intake of added sugars and saturated fatty acids.

The second study, also published in Nutrients, found that drinking watermelon juice for two weeks protects vascular function.

Dr. John A. Galat, cardiac surgeon at Novant Health, Charlotte, North Carolina, who was not involved in the studies, told Medical News Today:

“As the hot summer months approach these two studies, incidentally both funded by the National Watermelon Promotion Board, suggest that the regular enjoyment of watermelon might be good for you! In fact, over indulging likely would not have any adverse effects unlike so many other things that we enjoy.”

He noted, however, that based on these two studies alone, he would not necessarily promote watermelon consumption to those who don’t already enjoy the fruit.

For the first study, researchers analyzed data from 56,133 individuals from the National Health and Nutrition Examination Survey (NHANES) study.

They collated the data between 2003 and 2018, and included two 24-hour dietary recalls from individuals ages 2–18 years alongside adults.

The average watermelon consumption among adults and children was 125 and 162 grams per day. Around 98% of participants consumed raw watermelon, whereas 2% consumed watermelon juice.

By analyzing the dietary information, the researchers were able to estimate overall nutrient intake among watermelon consumers and non-consumers.

To ensure accuracy in their results, they controlled for factors including physical activity, poverty income ratio (PIR), smoking status and alcohol intake. They also controlled for the consumption of other foods, including total vegetables, non-watermelon fruits, and dairy intake.

In the end, they found that children and adults watermelon consumers had over 5% higher intake of:

They also had 5% lower intake of added sugars and total saturated fatty acids, and a higher intake of lycopene and other carotenoids.

The researchers noted their findings show that consuming watermelon may also be linked to adhering to overall dietary recommendations.

Dr. Michelle Pearlman, cofounder of Prime Institute and a board-certified gastroenterologist and physician nutritionist, who was also not involved in the study, told MNT that it remains unclear whether the outcomes are due to watermelon or an overall healthier diet.

“Those that eat watermelon and other fruits likely eat them to satisfy their sweet tooth. By eating fruits [they consume] less processed items that often contain high fructose corn syrup,” she said.

In the second study, researchers sought to understand more about the biological mechanisms underlying watermelons’ health benefits.

Autonomic dysfunction, which happens when the nerves of the autonomic nervous system are damaged, is linked to the development of cardiometabolic disease. Heart rate variability (HRV)—the variation from two consecutive heartbeats—is a simple and reliable method for assessing autonomic dysfunction.

Consumption of high quantities of sugar is shown to reduce HRV, vascular function, and microvascular blood flow. These effects are thought to be caused by reduced nitric oxide (NO) bioavailability.

Amino acid L-citrulline converts to L-arginine in the body, which promotes the formation of NO. Studies have found that NO-promoting therapies, including nitrates and beetroot juice, may improve HRV.

As watermelons are rich in L-citrulline and L-arginine, researchers investigated how consuming watermelon juice affects HRV after high glucose consumption.

To do so, they recruited 18 healthy men and women who were on average 23 years of age and had an average weight of 147 lbs. The participants were randomly assigned to either drink a 500ml watermelon juice or a placebo every day for two weeks.

In the end, the researchers found that drinking watermelon juice protects against impaired HRV following high sugar consumption.

“Although watermelon juice is known to contain high amounts of nitric acid precursors, it also contains antioxidants (like vitamin C) that can also affect nitric oxide. Because of this, the exact mechanism of action of watermelon juice in the control of heart rate variability was not clearly defined in this study,” Dr. Kelly Johnson-Arbor, medical toxicologist, co-medical director, and interim executive director at the National Capital Poison Center, who was not involved in the study, told MNT.

“Although this study did not conclusively prove an association between watermelon juice consumption and a decreased risk of cardiovascular disease, the results of this study suggest that further research should be performed to more extensively evaluate this possible connection.” — Dr. Kelly Johnson-Arbor

She added that further research is needed to see whether the findings apply to other age groups or those with other conditions such as obesity or underlying heart disease.

To understand more about watermelons’ potential health benefits, MNT spoke with Dr. Rigved Tadwalkar, a board-certified cardiologist at Providence Saint John’s Health Center in Santa Monica, California, who was not involved in these studies.

Dr. Tadwalkar said that some may not consider watermelon as part of a heart-healthy diet due to its high sugar content. He noted, however, that the sugars in the fruit have a low glycemic index meaning they impact blood sugar less than sugars from other sources.

He added that the fruit’s high fiber and water content may also mitigate the effects on blood sugar when consumed moderately.

“Beyond this, watermelon contains a variety of bioactive compounds that are good for the heart. [Lycopene, for example, carries antioxidant properties, and] has been associated with a reduced risk of cardiovascular disease, such as coronary artery disease and stroke.”— Dr. Rigved Tadwalkar

“The high potassium content of watermelon can help regulate blood pressure. High water content ensures proper hydration. Appropriate hydration is key for indirectly maintaining blood viscosity and reducing thrombosis,” he noted.

“Vitamin C found in watermelon supports endothelial health, maintaining the integrity of the blood vessels. There are a host of other vitamins and minerals found within watermelon that can provide potential cardiovascular benefits, including beta-carotene, vitamin B6, magnesium and folate,” he further explained.

When asked about a key takeaway from the studies, Dr. John P. Higgins, a sports cardiologist at McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), who was also not involved in these studies, told MNT that eating fruits has many health benefits.

“Eat more fruits each day, especially watermelon and the citrus fruits. It’s important to consider daily fruits as an important part of the diet as they are packed with antioxidants, anti-inflammatories, dietary fiber, and water—all of which can improve cardiovascular function, brain function, skin function, and reduce certain cancers.”— Dr. John P. Higgins

“[Fruits] also improve digestive health, boost our energy, and improve our mood. So remember the old saying ‘an apple a day keeps the doctor away’ but apply this now to all fruits ‘a few fruits a day keeps the doctor away’,” he said.

“If research with appropriate design and methodology continues to remain positive on watermelon consumption and its cardiovascular benefit, it may become a food that is a mainstay of a heart-healthy diet, especially given its wide availability and affordability,” Dr. Tadwalkar added.

“This is welcome news since many people enjoy consuming watermelon already. Nevertheless, additional investigation is required to establish clear guidelines and recommendations on how watermelon fits into a heart healthy diet.”— Dr. Rigved Tadwalkar