Nitric oxide (NO) is a simple gaseous molecule produced naturally by the body that acts as an important signaling molecule, particularly within the cardiovascular system. It is synthesized primarily by the cells lining the inner walls of blood vessels, known as the endothelium. This molecule is responsible for promoting vasodilation—the relaxation and widening of blood vessels—allowing for improved blood flow and nutrient delivery throughout the body. While the body produces its own supply of NO, diet significantly influences the available compounds needed to maintain optimal levels, supporting vascular health and overall circulation.
How Diet Boosts Nitric Oxide
The most potent way diet influences nitric oxide levels is through the nitrate-nitrite-nitric oxide pathway. This process begins when a person consumes foods rich in inorganic nitrate (\(\text{NO}_3^-\)), which is readily absorbed into the bloodstream. A significant portion of this circulating nitrate is then actively concentrated in the saliva.
The next step relies on commensal bacteria residing on the surface of the tongue. These microorganisms reduce the swallowed nitrate (\(\text{NO}_3^-\)) into nitrite (\(\text{NO}_2^-\)). Once the nitrite is swallowed, it enters the acidic environment of the stomach where it is rapidly converted into nitric oxide. This pathway is distinct from the body’s main NO production system and is effective at generating NO quickly, making dietary nitrate intake a valuable method for increasing its bioavailability.
Top Foods High in Nitrates
The foods that provide the greatest influx of inorganic nitrate are overwhelmingly vegetables, with leafy greens and root vegetables leading the concentration charts. Nitrate content can vary widely based on factors like soil quality, fertilizer use, and harvest time. However, green leafy vegetables consistently contain the highest average amount of these nitrate precursors.
Arugula stands out as a major whole-food source of nitrates, often packing around 480 mg per 100 grams. Other high-performing leafy greens include spinach and Swiss chard.
Root vegetables are the next significant category, most notably beets and concentrated beet juice. Beets typically contain between 110 to 177 mg of nitrates per 100 grams, with the juice providing a highly concentrated dose often used by athletes. Celery and carrots are also strong contributors of inorganic nitrates, alongside parsley and bok choy.
Preparation methods impact the final nitrate content of vegetables. While boiling may reduce nitrate levels by nearly half, consuming high-nitrate vegetables raw, such as in a salad or as fresh juice, generally ensures the greatest retention of the precursor compounds.
Sources of Amino Acid Precursors and Co-Factors
Beyond the nitrate pathway, the body has a primary internal mechanism for NO production that relies on the amino acid L-Arginine. This process, catalyzed by enzymes called nitric oxide synthases (NOS), converts L-Arginine into L-Citrulline and nitric oxide. Consuming protein-rich foods helps ensure an adequate supply of L-Arginine for this endogenous production pathway.
L-Arginine Sources
Although the body can synthesize L-Arginine, it is considered conditionally essential, meaning that under certain conditions like illness or high stress, dietary intake becomes important. Foods rich in L-Arginine include:
- Nuts (walnuts and peanuts)
- Seeds (pumpkin and sunflower seeds)
- Protein sources (turkey and chicken)
- Legumes (chickpeas and lentils)
L-Citrulline and Co-Factors
L-Citrulline is an amino acid precursor because the body can efficiently recycle it back into L-Arginine, which helps sustain the NOS pathway. Watermelon is the most widely recognized food source of L-Citrulline, along with cucumbers and pomegranates.
Co-factors are necessary to ensure NO production pathways function efficiently and that the resulting NO molecule remains stable. Antioxidant vitamins, particularly Vitamin C, help regenerate a necessary co-factor for the NOS enzyme and protect NO from breaking down too quickly. Foods high in Vitamin C (like citrus fruits and bell peppers) and polyphenol-rich items (such as berries and dark chocolate) indirectly support healthy nitric oxide levels.