Can watermelon consumption lower blood pressure?

How does watermelon actually lower blood pressure?

Watermelon is a natural source of L-citrulline, an amino acid your body converts into L-arginine. L-arginine is the raw material your blood vessels use to make nitric oxide, a molecule that signals the inner lining of your arteries to relax and widen — a process called vasodilation. Wider vessels mean lower resistance to blood flow, which directly reduces blood pressure. A 2025 pilot trial showed that after four weeks of eating watermelon, participants had higher levels of L-arginine and a better L-arginine/ADMA ratio (ADMA is a compound that blocks nitric oxide production), indicating improved nitric oxide synthesis capacity [2].

This mechanism is backed by a 2011 pilot study in people with prehypertension (slightly elevated blood pressure, around 134/77 mmHg). After six weeks of watermelon supplementation, aortic systolic pressure dropped by 7 mmHg and the augmentation index (a measure of arterial stiffness) improved by 6% [7]. These changes mean the heart doesn't have to work as hard to pump blood.

How much watermelon do you need to eat, and who benefits most?

The strongest evidence points to benefits in middle-aged and older adults. A 2025 meta-analysis of 15 randomized controlled trials involving 415 participants found that watermelon or L-citrulline supplementation lowered systolic blood pressure by an average of 4 mmHg and diastolic by 2.5 mmHg in this age group [1]. When L-citrulline was combined with L-arginine (another amino acid), the effect was even larger: systolic dropped by 10.4 mmHg and diastolic by 4.9 mmHg [1]. This suggests that eating watermelon alongside other arginine-rich foods (like nuts, seeds, or fish) may boost the effect.

Dose matters, but the research isn't perfectly clear on the exact amount. A 2025 study in firefighters found that 500 mL (about 2 cups) of watermelon juice daily for four weeks significantly lowered mean blood pressure [4]. A 2024 study in pregnant women used 700 mL daily and also saw significant drops [6]. However, a 2025 dose-response trial comparing 1 cup (152 g) versus 2 cups (304 g) of watermelon flesh found no statistically significant difference in 24-hour ambulatory blood pressure between the groups, though the higher dose group did show improvements in nitric oxide precursors [2]. The takeaway: consistent daily intake of at least 1-2 cups of watermelon or its juice appears beneficial, but more is not necessarily dramatically better.

Is it just the citrulline, or do other compounds in watermelon help?

Watermelon also contains quercetin, a plant compound with its own blood-pressure-lowering effects. A 2022 meta-analysis of 10 trials found that quercetin supplementation reduced systolic blood pressure by about 2.4 mmHg in the general population and diastolic by 3.1 mmHg in people with prehypertension or hypertension [3]. While the amount of quercetin in watermelon is modest compared to supplements, it likely adds to the overall effect.

Additionally, watermelon is rich in potassium and lycopene. Potassium helps counterbalance sodium's blood-pressure-raising effects, and lycopene is an antioxidant that supports blood vessel health. A 2025 study in elderly hypertensive patients found that drinking watermelon juice for just seven days dropped average systolic pressure from 168 mmHg to 135 mmHg and diastolic from 99 mmHg to 85.5 mmHg [5]. While this dramatic drop may partly reflect the short-term nature of the study and the high starting blood pressure, it illustrates the potential of watermelon as a complementary dietary strategy.

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