"The pressure on the aorta and on the heart decreased after consuming watermelon extract," Florida State University Associate Professor Arturo Figuero said.
Researchers noted that more people die of heart attacks in cold weather because the stress of the cold temperatures causes blood pressure to increase and the heart has to work harder to pump blood into the aorta.
That often leads to less blood flow to the heart.
Thus, people with obesity and high blood pressure face a higher risk for stroke or heart attack when exposed to the cold, researchers said.
Figueroa's 12-week study focused on 13 middle-aged, obese men and women who also suffered from high blood pressure.
To simulate cold weather conditions, one hand of the subject was dipped into water (or 4 degrees Celsius) while Figueroa's team took their blood pressure and other vital measurements.
The group was divided into two. For the first six weeks, one group was given four grammes of the amino acid L-citrulline and two grammes of L-arginine per day, both from watermelon extract. The other group was given a placebo for 6 weeks.
Participants also had to refrain from taking any medication for blood pressure or making any significant changes in their lifestyle, particularly related to diet and exercise, during the study.
The results showed that consuming watermelon had a positive impact on aortic blood pressure and other vascular parameters.
Notably, study participants showed improvements in blood pressure and cardiac stress while both at rest and while they were exposed to the cold water.
"That means less overload to the heart, so the heart is going to work easily during a stressful situation such as cold exposure," Figueroa said.
The study was published in the American Journal of Hypertension.