Answer: Beets, leafy greens such as spinach and arugula, and watermelon support nitric oxide in two ways. Beets and greens are rich in dietary nitrate, which mouth bacteria and the body convert into nitric oxide. Watermelon provides citrulline, which the kidneys turn into arginine. Studies on beetroot and blood pressure are encouraging but often small, so think of these foods as part of an overall healthy pattern.
- Beets and leafy greens supply dietary nitrate.
- Watermelon supplies citrulline, a source of arginine.
- Antibacterial mouthwash may blunt nitrate conversion.
- Foods work best within a DASH-style eating pattern.
Two food routes to nitric oxide
Your body has two main ways to make nitric oxide. The first is the enzyme route in the lining of blood vessels, which uses arginine. The second is the nitrate route: nitrate from vegetables is turned into nitrite by bacteria on the tongue, then into nitric oxide in the body, particularly where oxygen is low.
Foods can feed both. Beets and leafy greens are among the richest sources of nitrate. Watermelon is the best known food source of citrulline, which the kidneys convert into arginine for the enzyme route. Protein foods such as fish, beans and nuts provide arginine directly. Our nitric oxide explainer covers the enzyme route in detail.
Beets: the most studied nitric oxide food
Beetroot, as whole beets or juice, is the most researched nitrate food. Trials listed in a PubMed search on dietary nitrate and blood pressure have tested beetroot juice on blood pressure and exercise, with several reporting modest short-term reductions in blood pressure. Many studies are small and short, and results vary with the amount of nitrate and the people studied.
Practical notes: beets can turn urine and stools pink or red, which is harmless. Beet juice can be high in natural sugar, so whole beets or small servings make sense for people watching blood sugar. Beets are also fairly high in oxalate, which matters for people prone to certain kidney stones.
Leafy greens and other nitrate vegetables
Arugula, spinach, lettuce, Swiss chard, celery and bok choy are all good nitrate sources, often comparable to beets per serving. They also bring potassium, magnesium and fiber, nutrients that matter for blood pressure in their own right.
One detail people miss: strong antibacterial mouthwash can reduce the mouth bacteria that convert nitrate to nitrite. If you rely on nitrate foods, ask your dentist whether daily antiseptic rinse is necessary for you.
A note for people on warfarin: leafy greens are high in vitamin K. You do not need to avoid them, but keep your intake consistent and tell your doctor about big changes. Our potassium guide covers cautions for people with kidney disease.
| Food | Main nitric oxide route | Practical note |
|---|---|---|
| Beets and beet juice | Dietary nitrate | Juice can be high in sugar |
| Arugula, spinach, lettuce | Dietary nitrate | Keep vitamin K steady on warfarin |
| Celery, chard, bok choy | Dietary nitrate | Also bring potassium and fiber |
| Watermelon | Citrulline to arginine | Rind has more citrulline |
| Fish, beans, nuts | Arginine | Part of normal protein intake |
Watermelon and citrulline
Watermelon contains citrulline, with more in the pale rind near the skin than in the red flesh. After you eat it, citrulline is converted to arginine in the kidneys, adding to the raw material for nitric oxide.
The amounts in a typical serving are smaller than in most citrulline supplements, but watermelon brings water, potassium and very few calories, so it earns its place regardless. You can blend some rind into a smoothie or pickle it.
Here is a worked example of a day we would sketch: arugula and beet salad at lunch, a handful of walnuts in the afternoon, salmon with spinach at dinner, and watermelon for dessert. That single day covers both routes, with no supplement needed. It fits well with the NHLBI DASH Eating Plan, which emphasizes vegetables, fruit and lower sodium.
Where a daily capsule fits beside these foods
Food comes first. A capsule like Melonex contains arginine AKG, arginine HCl and citrulline malate, so it supplies the arginine route but not dietary nitrate. It cannot replace a plate of vegetables, and it is not intended to. See Melonex ingredients for exactly what the brand lists.
We see it as an optional add-on for people who already eat reasonably well, walk regularly and have talked with their doctor. Trials of arginine and citrulline supplements are small and mixed. If you are curious, the What is Melonex page gives an overview, and the Melonex sale page lists package prices with no auto-ship.
Limits and who should take care
Nitrate foods are safe for most people, but they are not a treatment. If your blood pressure is high, the foods support the plan your doctor gives you; they do not replace medicine. Beetroot juice in large amounts may add to the effect of blood pressure medicine, so mention it if you drink it daily.
Supplement cautions are stricter: ask a doctor before arginine or citrulline if you take blood pressure medicine, nitrates, erectile dysfunction medicine, blood thinners or diabetes medicine, or have kidney, liver or heart disease. Our guide on amino acid supplement interactions explains why.
Food first, then consider extras
Curious about a capsule as well? Start at the Melonex official website.
Order MelonexFrequently asked questions
Which food boosts nitric oxide the most?
Beets and leafy greens such as arugula and spinach are among the richest nitrate sources. Variety matters more than one superfood.
Does cooking destroy nitrate in vegetables?
Boiling can leach some nitrate into the water. Raw, steamed or roasted vegetables keep more of it.
Can foods replace a nitric oxide supplement?
For most people, a vegetable-rich diet is a stronger foundation than any capsule. A supplement is an optional extra.