Watermelon juice and heart rate during a glucose drink
What it found
In 18 healthy young adults, two weeks of daily watermelon juice helped keep some heart rate variability measures steady during a glucose drink, compared with a placebo.
It made no difference to energy use or fat and carbohydrate burning.
What they found
Studies in people
Heart rate variability
During the glucose challenge, watermelon juice preserved high-frequency power and pNN50 compared with placebo. The authors say this suggests the juice helped keep parasympathetic activity up.
Other HRV measures
SDNN and RMSSD dropped during the glucose challenge but were not different between the watermelon juice and placebo treatments. Heart rate rose during the challenge to a similar degree in both groups.
Energy use
Resting energy expenditure rose during the glucose challenge, but there was no difference between the watermelon juice and placebo treatments.
Fuel burning
Carbohydrate oxidation went up and fat oxidation went down during the glucose challenge, with no difference between the two treatments. Metabolic flexibility was also about the same.
Links between measures
Energy expenditure and fuel burning showed only modest links with heart rate variability measures. There were no significant treatment effects for these relationships.
What the authors conclude
“We report that WMJ supplementation attenuates OGC-induced reductions in HRV.”
Also in their conclusions
- They conclude that the autonomic system is susceptible to a hyperglycemic episode.
- They say their rigorous study design shows that a naturally rich source of the amino acids L-citrulline and L-arginine can preserve heart rate variability during a hyperglycemic episode.
- They add that more work is required to understand how this relationship works.
How it was done
The authors wanted to see whether watermelon juice, a natural source of the amino acids L-citrulline and L-arginine, could protect heart rate variability during a short rise in blood sugar. They also wanted to check whether it changed the body's metabolic response.
They ran a randomised, double-blind, placebo-controlled crossover trial in 18 healthy young men and women with a normal BMI. Participants drank 500 mL of watermelon juice or a placebo daily for 2 weeks, then did a 75 g glucose challenge, and later switched to the other drink after a 2-week washout.
What it can’t tell you
- The study cannot directly link improved nitric oxide levels to the preservation of heart rate variability.
- Watermelon is also rich in vitamin C and lycopene, so the authors cannot rule out that these played a role.
- The small sample size means the results may not apply to everyone, and the study could not determine the impact of sex.
Who paid
- Funding
- Funded by NIGMS NIH HHS (from the PubMed record).
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Louisiana State University, USA; Columbus State University, USA; Pennington Biomedical Research Center, USA
The paper
- Title
- The Effect of Watermelon Juice Supplementation on Heart Rate Variability and Metabolic Response during an Oral Glucose Challenge: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Matthews R, Early KS, Vincellette CM, et al (2023). The Effect of Watermelon Juice Supplementation on Heart Rate Variability and Metabolic Response during an Oral Glucose Challenge: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial. Nutrients. doi:10.3390/nu15040810Free full textPubMed 36839167DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error