The Citrulline Effect: Why a Serving of Watermelon Can Boost Your Energy and Spirits

A study published in Current Developments in Nutrition examined whether daily consumption of fresh watermelon could impact sexual health and mental well-being in sexually active overweight adults. The authors used a crossover design: each participant completed a “watermelon” phase and a control phase, which allows for comparison of changes within the same person. The primary outcomes were assessed using validated questionnaires on sexual functioning and mental health after 4-week periods. The article describes measurements before and after each phase and tests whether the effect matches a biologically plausible hypothesis - watermelon is rich in L-citrulline, a precursor of L-arginine and nitric oxide (NO), which are important for vascular response and libido.

Background of the study

The relationship between nutrition and psychosexual well-being in adults often passes through vascular and neurotransmitter regulation. Watermelon is interesting as a “whole food carrier” of the amino acid L-citrulline, a precursor of L-arginine and nitric oxide (NO) - a key vasodilator on which microcirculation, erectile function and, in part, mood and stress resistance depend. Accumulating data in people and in reviews show that watermelon and/or citrulline are able to increase the bioavailability of NO and improve vascular reactivity, which became the biological prerequisite for testing mental and sexual outcomes against the background of regular consumption of fresh watermelon.

In clinical nutrition studies in overweight adults, a daily serving of watermelon for four weeks was already associated with reduced body weight and systolic blood pressure, increased satiety, and increased blood antioxidant capacity compared to an isocaloric sugary snack. These results, obtained in randomized crossover designs, supported the idea that replacing “empty” snacks with a whole food rich in citrulline, lycopene, and potassium may gently improve cardiometabolic parameters - and therefore it was logical to test the vascular tone-related aspects of sexual health.

Against this backdrop, a new paper in Current Developments in Nutrition uses a crossover design in sexually active, overweight adults: each participant undergoes a watermelon phase and a control phase, allowing for within-person comparisons and reducing the influence of external factors (stress, sleep, seasonality). Outcomes are assessed with validated questionnaires of sexual function and mental health after 4-week periods—an approach that is closer to real life than citrulline capsules, while also being compatible with the NO-dependent vasodilation mechanism.

It is also important to consider the funding context: watermelon research is often supported by the National Watermelon Promotion Board, which emphasizes the need for transparent methodology, pre-registration, and independent replication. However, the hypothesis itself is based not on marketing claims, but on the citrulline → arginine → NO conversion previously demonstrated in human experiments (watermelon juice/puree, citrulline supplements) and links to vascular effects. The new study essentially transfers this mechanism to “superstructure” - mental and sexual - outcomes, which are especially relevant for people with excess weight.

Why is this important?

Sexual health and mood issues often coexist with excess weight: endothelial dysfunction, chronic low-grade inflammation, and stress all play a role. If a whole food like watermelon can gently improve vascular reactivity and well-being, this opens up an accessible, safe preventive tool. There are prerequisites: in humans, watermelon and watermelon drinks increased the bioavailability of NO, improved some parameters of vascular function, and reduced blood pressure in short interventions; L-citrulline alone showed signals of benefit in mild erectile dysfunction. These observations led the researchers to the “whole watermelon → vessels/mood/sex” test.

How it was done

According to the description, this is a randomized crossover clinical trial: overweight participants who are sexually active sequentially underwent two 4-week phases - with a daily portion of fresh watermelon and a control phase, in a randomized order. This design minimizes the influence of "foreign" factors (stress, sleep, seasonality), because each serves as their own control. In parallel, diet and lifestyle were recorded in order to correctly interpret changes in sexual and mental health indicators. According to the bibliographic card, the work was published in 2025 (volume 9, article No. 106278).

What is already known in the context of this work

A group of authors previously showed that four weeks of daily watermelon consumption in overweight adults reduced body weight and systolic blood pressure, increased satiety, and increased antioxidant capacity in the blood compared to an isocaloric sweet snack. Other studies reported that 100% watermelon juice improved vascular function in postmenopausal women, and citrulline tablets improved erectile rigidity in men with mild ED. Together, this paints a biochemical bridge: citrulline → arginine → NO → better microcirculation and endothelial response, which could theoretically “drive” both sexual function and subjective well-being.

What mechanisms are plausible here?

Watermelon is not only water and sugar. It is rich in citrulline and lycopene, contains potassium, magnesium, polyphenols and carotenoids. Citrulline increases the availability of arginine and the production of nitric oxide, improving vasodilation, which is critical for sexual function in both sexes; antioxidants and electrolytes support the endothelium and vegetative balance, and the high water content of the fruit helps hydration, indirectly affecting both endurance and mood. This “package of effects” makes watermelon a convenient food carrier for gentle correction of vascular and psychoemotional parameters without pharmacotherapy.

What this means for practice (with caveats)

If you’re an overweight adult looking to “tighten up” your well-being, sleep, and sex life, a daily serving of fresh watermelon may be a sensible part of a strategy along with exercise, sleep, and stress management. But it’s important to understand the limits: Short-term dietary interventions are not a cure for ED or depression, but an adjuvant to fundamental habits and medical care when needed. The key to benefit is replacing less-healthy snacks with watermelon (not adding extra calories on top) and sticking with it.

Limitations and transparency

The study is short (weeks rather than months), likely small in sample size, and relies on self-report questionnaires - this limits causal inference and generalizability. The project summary indicates industry funding (National Watermelon Promotion Board), which requires increased attention to methodology, pre-registration, and independent replication of results. Longer, larger RCTs with clinical rather than just questionnaire outcomes and clear calorie substitution are needed to separate the "watermelon effect" from the "cookie displacement effect."

Conclusion

The new paper adds a human layer to the idea that whole citrulline-rich foods can gently affect vascular and psychoemotional markers. It’s not “natural Viagra,” but it’s a smart nutritional tactic: eating a serving of fresh watermelon instead of a sugary, empty snack can help support blood pressure, vascular response, mood, and perhaps sex life. Bigger, longer studies are on the way.

Study source: Mee Young Hong et al. The Role of Fresh Watermelon on Mental and Sexual Health: A Crossover Study in Overweight Sexually Active Adults. Current Developments in Nutrition. 2025;9:106278. DOI: 10.1016/j.cdnut.2025.106278