Quick Facts

• Two weeks of daily watermelon juice preserved heart rate variability during glucose challenges in healthy adults
• The protective effect comes from watermelon’s high citrulline and arginine content, which boost nitric oxide production
• Heart rate variability is a key marker of cardiovascular health and nervous system function

Daily watermelon juice consumption helps maintain heart rate variability during blood sugar spikes, according to new research from Louisiana State University and Columbus State University.

The randomized, double-blind study tested 18 healthy adults aged 18 to 40. Participants consumed 500 ml of watermelon juice daily for two weeks, then underwent a glucose tolerance test. Researchers measured heart rate variability before and after the glucose challenge.

Watermelon juice preserved two key heart rate variability measures compared to placebo. High-frequency power remained stable, as did pNN50, which tracks consecutive heartbeat variations. Both measures typically decline when blood sugar rises.

“After two weeks of watermelon juice, participants showed a much steadier HRV, even in the face of that sugar load. Their nervous systems stayed calmer and more balanced,” the researchers noted.

Heart rate variability measures the variation between consecutive heartbeats. Higher variability indicates better cardiovascular health and nervous system adaptability. Low heart rate variability links to increased cardiometabolic disease risk.

The protective effects stem from watermelon’s unique amino acid profile. Watermelon contains high levels of citrulline and arginine, which convert to nitric oxide in the body. This molecule helps blood vessels dilate and improves circulation.

Dr. Kelly Johnson-Arbor, a medical toxicologist not involved in the study, noted watermelon’s antioxidant content also affects nitric oxide. “The exact mechanism of action of watermelon juice in the control of heart rate variability was not clearly defined in this study,” she said.

The study was funded by the National Watermelon Promotion Board, which has invested nearly $1.5 million in nutrition research over 20 years. The board recently received USDA approval to increase industry assessments to fund additional research.

Lead researcher Dr. Timothy Allerton plans to expand the research to athletes. The board will award up to $125,000 per project for studies investigating watermelon’s health benefits, with proposals due December 1, 2025.

Blood sugar spikes typically suppress heart rate variability. Over time, frequent spikes can damage the body’s regulatory systems. The research suggests watermelon juice might help protect against this damage.

The study adds to growing evidence that foods rich in nitric oxide-boosting compounds affect nervous system and cardiovascular function. However, researchers emphasize more extensive studies are needed to establish clinical recommendations.

Read more: This Delicious Fruit May Help Balance Blood Sugar & Boost HRV