Nitric Oxide: The Quiet Molecule Behind Circulation and Healing

A few weeks ago we looked at a small sprinting study...

...the question was whether a nitric-oxide-supporting supplement could help athletes repeat a maximal effort. That paper was about performance, not healing. But it kept pointing at something underneath both: a tiny molecule called nitric oxide.

So we pulled the thread. A few more papers let us follow it properly, and just as important ,show you exactly where the science is solid and where it's still only hopeful.

Let's start with the molecule itself.

What is nitric oxide, really?

Nitric oxide (NO) is a small signaling molecule your body makes on demand. Its discovery as a biological messenger was a big enough deal to earn a Nobel Prize in 1998 (Ahmed et al., 2022). For our purposes, its most important job is simple to state: it relaxes and widens blood vessels, which improves blood flow.

But it doesn't stop there. NO helps build new blood vessels (a process called angiogenesis), supports the immune response, has direct antimicrobial activity, and pitches in on collagen formation (Malone-Povolny et al., 2019; Ahmed et al., 2022). Think about what that list adds up to.

NO sits right at the intersection of the two things that matter most in wound care and surgical recovery: getting blood to tissue, and rebuilding that tissue. No wonder it's worth paying attention to.

So where does it come from? Your body makes NO from the amino acid L-arginine, using a family of enzymes called nitric oxide synthases. But here's the interesting part, that's not the only road in.

Three roads to the same molecule

This is where it gets practically useful. There isn't one way to support nitric oxide. There are several, and they're genuinely different from one another.

The arginine route. Citrulline - from supplements, or from watermelon converts to arginine, which your enzymes then turn into NO. This is the pathway behind the sprint study, and behind decades of arginine wound-healing research.

The dietary nitrate route. Leafy greens and beetroot are loaded with nitrate, which the body converts to nitrite and then to NO. This is a completely separate road, and it doesn't lean on those same enzymes. Why does that matter? Because in diabetes the enzyme route is impaired — so a route that skips the enzymes entirely may offer a workaround.

The polyphenol route. Compounds in foods like tart cherry appear to support the specific enzyme that makes NO in blood vessel walls (eNOS), while separately calming inflammation and oxidative stress through their own mechanisms (Ngo et al., 2026).

Same destination, three different ways in. That redundancy is exactly why nitric oxide is such an interesting target and why it's worth understanding the system rather than chasing any single product.

Where the evidence is genuinely strong: the diabetic wound

Two detailed reviews - one from UNC Chapel Hill (Malone-Povolny and colleagues, 2019) and one from Qatar University (Ahmed and colleagues, 2022) - build a compelling biological case. Picture a healthy wound for a moment. The body ramps NO up to clear bacteria, then dials it back down to rebuild. It's a controlled, two-phase response.

Now picture a diabetic wound. Chronic high blood sugar damages the very enzyme that produces NO, so the wound is effectively running NO-starved. Lower NO means poorer circulation, weaker bacterial clearance, less collagen, and healing that stalls out.

That's a well-established biology that helps explain why diabetic foot ulcers are so stubborn. Diabetic wound fluid has actually been measured carrying lower NO than healthy wound fluid (Malone-Povolny et al., 2019). From there, the reviews walk through years of work delivering NO straight to wounds through specialized dressings, gels, and nanoparticles, with consistent improvements in animal models and some promising human results for infected, non-healing wounds (Ahmed et al., 2022).

Where the evidence gets thinner: from lab bench to patient

Now for the honest part, and to their credit, both reviews say it themselves.

Almost all of this work was done in rodents. And rodent skin doesn't heal the way ours does: rodents pull their wounds closed by contraction, while we re-epithelialize. The UNC review is refreshingly direct that pigs, not mice, are the gold-standard model for predicting what works in people, and that much of the field simply hasn't gotten there yet (Malone-Povolny et al., 2019).

The oral-supplement evidence calls for even more caution. The largest human trial of arginine supplementation in diabetic foot ulcers - 270 patients, found no overall healing benefit. The only improvement showed up in a subgroup whose limbs already had poor circulation (Armstrong et al., 2014, as reviewed in Malone-Povolny et al., 2019).

Read that carefully: it's a meaningful signal for a specific patient, not a blanket endorsement for everyone.

One more note, in the spirit of telling you who's writing. The UNC review's senior author co-founded companies that commercialize nitric-oxide technology. The science holds up on its own, but you deserve to know that, and to weigh it yourself.

The orthopedic angle: promising, and worth watching

The orthopedic side of this story is a little more encouraging, though still early. The same arginine we've been tracing turns up in a 2023 review in the Journal of the American Academy of Orthopaedic Surgeons, which looks at targeted amino acid supplementation around orthopedic surgery (Jazayeri et al., 2023).

The mechanism is the one we already know: arginine feeds nitric oxide synthesis, which improves blood flow to healing tissue. But it does something else useful too - arginine is also a precursor to proline, the raw material for collagen, and one cited study found roughly a 67% increase in subcutaneous collagen deposition after two weeks of supplementation (Jazayeri et al., 2023).

What makes this setting different from the diabetic ulcer is that the human evidence is friendlier. Across several randomized trials, essential and conditionally-essential amino acids reduced muscle loss and sped functional recovery after procedures like knee replacement and hip fracture fixation, one trial even lowered postoperative complications, with no reported adverse events (Jazayeri et al., 2023).

Surgery triggers a hypermetabolic, muscle-wasting state, and feeding the building blocks back in appears to blunt it. Two honest caveats, though: this is a narrative review leaning on mostly small trials, so it's encouraging rather than settled, and consistent with the disclosure we made above, the senior author reports financial relationships in orthopedics, none tied to amino acids specifically (Jazayeri et al., 2023).

A separate, more speculative thread asks whether tart cherry could help surgical patients recover, given its NO support, anti-inflammatory and antioxidant effects, and a little natural melatonin for sleep (Ngo et al., 2026). The reasoning is appealing, and tart cherry has real evidence in athletes and osteoarthritis patients for reduced soreness.

But the authors hold the line, and we'll echo it: neither of these clinical trials tested it in surgical patients. They call it strictly "investigational," and warn, repeatedly, that a plausible mechanism is not proof of clinical benefit (Ngo et al., 2026).

So what does this mean for podiatry, wound care, and orthopedics?

Step back, and a coherent picture comes into focus.

Nitric oxide is real, central, and measurable in wound healing and circulation. The pathways to support it are diverse, which is genuinely encouraging, especially the nitrate route in diabetes, where the usual enzyme route is broken. And targeted nutritional and perioperative support is an area of active, legitimate research.

At the same time, the gap between "biologically plausible" and "proven to help my patient" is wide, and it deserves respect. The strongest evidence is for engineered NO delivered topically to chronic wounds; the perioperative amino-acid work is promising but still early; and the weakest case of all is for any single supplement changing surgical outcomes on its own. Those things can all be true at once, and good clinical thinking means holding them together rather than picking the one you like.

For now, here's the durable takeaway, and it's the one the molecule itself keeps teaching: circulation underlies healing. Anything that genuinely improves perfusion to compromised tissue, whether it's a dressing, a nutrient, or simply better diabetes control, is working on the right problem. The science of doing that reliably is still being written. We'll keep reading it as it comes, and we'll keep telling you what it actually says.

References:

Ahmed, R., et al. (2022). Nitric oxide-releasing biomaterials for promoting wound healing in impaired diabetic wounds: State of the art and recent trends. Biomedicine & Pharmacotherapy, 149, 112707.

Jazayeri, R., Anil, U., & Zuckerman, J. D. (2023). The role of amino acid supplementation in orthopaedic surgery. Journal of the American Academy of Orthopaedic Surgeons, 31(00), 1–7.

Malone-Povolny, M. J., Maloney, S. E., & Schoenfisch, M. H. (2019). Nitric oxide therapy for diabetic wound healing. Advanced Healthcare Materials, 8(12), e1801210.

Ngo, A. L., Tadakamalla, R., Shahbendeh, C., & Nichols, J. (2026). Tart cherry supplementation in postoperative orthopedic recovery: A narrative review of a novel anti-inflammatory adjunct. Journal of Orthopaedic Experience & Innovation, 7(1).

Armstrong, D. G., et al. (2014). Effect of oral nutritional supplementation on wound healing in diabetic foot ulcers: A prospective randomized controlled trial. Diabetic Medicine, 31(9), 1069–1077.