Watermelon has not been proven to increase testosterone in any meaningful way. One small study in overweight adults found that testosterone showed a slight upward trend in men after watermelon consumption, but the result was not statistically significant (p = 0.094), meaning it could easily have been due to chance. There is no strong human evidence that eating watermelon will raise your testosterone levels.
That said, watermelon does contain compounds that support male reproductive health through other pathways, particularly blood flow and sperm quality. Understanding the difference between those effects and actual hormone production is key to making sense of the claims you’ll find online.
What the Research Actually Found
The most directly relevant study, conducted at San Diego State University, measured sex hormones in overweight adults after fresh watermelon consumption. Testosterone levels in male participants trended upward, but the change fell short of statistical significance. In plain terms, the bump was too small and too inconsistent across participants to conclude that watermelon caused it. Estradiol (a form of estrogen) did increase significantly in female participants, but no improvements showed up on sexual health questionnaires for either group.
A separate study in camels found that a single intravenous dose of L-citrulline, a key amino acid in watermelon, raised both testosterone and estradiol while boosting blood flow to the testes. That’s an interesting biological signal, but injecting a concentrated amino acid directly into the bloodstream of a camel is a far cry from eating a few slices of watermelon. The leap from that finding to practical dietary advice for humans isn’t supported.
Citrulline, Nitric Oxide, and Blood Flow
Most of the health buzz around watermelon and male sexual health comes from its citrulline content. Citrulline is an amino acid that your kidneys convert into arginine, which in turn helps produce nitric oxide. Nitric oxide relaxes blood vessel walls, increasing blood flow throughout the body, including to the penis. This is the same basic mechanism targeted by common erectile dysfunction medications.
Watermelon flesh contains the highest concentration of citrulline compared to the rind and seeds, though the rind is also a notable source when measured per calorie. Citrulline from watermelon bypasses the liver without being broken down, which makes it surprisingly efficient at raising arginine levels in the blood. In fact, dietary citrulline may be better at boosting arginine availability than taking arginine supplements directly, because supplemental arginine gets partially broken down by enzymes in the gut and liver before it reaches your circulation.
One longer-term study found that watermelon consumption significantly raised circulating citrulline levels. However, improving blood flow is not the same thing as increasing testosterone. These are two distinct biological pathways. Better blood flow can improve erection quality without changing hormone levels at all.
How Much Citrulline You’d Need
In a clinical trial of men with mild erectile dysfunction, a daily dose of 1.5 grams of L-citrulline for one month improved erection hardness in 50% of participants, compared to just 8% on placebo. That’s a notable result, but getting 1.5 grams of citrulline from watermelon alone would require eating a substantial amount of fruit every day. Watermelon flesh contains roughly 10 mg of citrulline per 100 calories. You’d need to eat several cups daily to approach a therapeutic dose, and even then, you’d be supporting blood flow rather than boosting testosterone.
Lycopene and Sperm Quality
Watermelon is one of the richest sources of lycopene, the pigment responsible for its red color. Lycopene has a stronger ability to neutralize harmful reactive molecules than most other antioxidants in its class, thanks to its chemical structure. This matters for male reproductive health because sperm cells are especially vulnerable to oxidative damage.
A meta-analysis pooling data from multiple studies found that lycopene supplementation significantly improved sperm concentration and certain aspects of sperm motility. One trial also found improvements in sperm shape and the proportion of fast-moving sperm. These benefits appear to come from lycopene’s ability to reduce inflammation and protect the energy-producing structures inside sperm cells. Again, these are real benefits for male fertility, but they operate through antioxidant and anti-inflammatory pathways rather than by raising testosterone.
Sugar and Metabolic Considerations
Watermelon has a high glycemic index of 80, which sounds alarming if you’re concerned about insulin and metabolic health. But a typical serving contains so little carbohydrate that its glycemic load is only 5, which is low. In practical terms, eating watermelon in normal portions doesn’t cause the kind of blood sugar spike that would work against hormonal health. The total amount of carbohydrate in your overall diet matters far more than the glycemic index of any single food, and maintaining a healthy weight is the most important dietary factor for keeping testosterone levels in a normal range.
Watermelon vs. Citrulline Supplements
If your goal is to get enough citrulline to meaningfully affect blood flow, supplements are more practical than watermelon. Concentrated L-citrulline supplements deliver grams of the amino acid in a single dose, while you’d need to eat large quantities of fruit to match that. Supplements produced dramatically higher short-term spikes in blood citrulline levels in clinical comparisons. Watermelon, on the other hand, was better at raising citrulline levels over the long term in one study, possibly because the fruit’s other nutrients and fiber slow absorption.
Whole watermelon does offer lycopene, vitamins A and C, and hydration that a citrulline capsule doesn’t. If you enjoy watermelon and want to include it as part of a diet that supports overall health, it’s a reasonable choice. Just don’t expect it to function as a testosterone booster. The honest summary: watermelon can modestly support blood flow and sperm quality, but its effect on testosterone itself remains unproven.