L-citrulline is found naturally in watermelon. Recently interest has increased for this amino acid due to potential health benefits. Notably, L-citrulline has the potential to lead to dilation of blood vessels due to its involvement in the production of nitric oxide.

The study will be an acute single blind, randomised controlled, crossover intervention study in healthy, young volunteers. Participants receive either the test watermelon drink or control drink (water). Blood samples and vascular measures (by a single-cuff based method) will be measured at baseline. Vascular measures will be repeated at 15-minute intervals between 0-2 hours and a second blood sample will be drawn at 1.5 hours to coincide with the estimated peak plasma L-citrulline. Citrulline, arginine and nitric oxide metabolites will be measured in the blood samples.

Inclusion Criteria:

• Males and females
• 18-30 years
• Healthy (as per exclusion criteria)
• Able to understand information sheet
• Willing to comply with the study protocol
• Able to give informed consent.

Exclusion Criteria:

• Medical history of myocardial infarction
• Medical history of angina
• Medical history of thrombosis
• Medical history of stroke
• Medical history of cancer
• Medical history of high cholesterol
• Medical history of liver diseases
• Medical history of renal diseases
• Medical history of respiratory diseases
• Medical history of bowel diseases
• Medical history of diabetes
• Medical history of other endocrine disorders
• BMI <18.5 kg/m2 or >25 kg/m2
• Blood pressure <90/60 or > 140/90 mmHg
• Current use of antihypertensive medication
• Pregnant or lactating
• Alcohol intake > 14 units/week
• Cigarette smoker (or quit within the last 6 months)
• Vigorous exercise > 3 times/ week