I've become obsessed with Nitric oxide, or 'NO'. It's a gas produced in the lining of your blood vessels, called the endothelium. Its main job is vasodilation, which means signalling blood vessels to relax and widen. The result is better circulation, more oxygen delivery, and more efficient removal of waste products from working muscles. Your body makes NO through a few different pathways. The one most supplement users care about starts with L-arginine, an amino acid that gets converted into nitric oxide. L-citrulline is converted into L-arginine in the kidneys, so it acts as an indirect but often more efficient booster. Beetroot works through a completely separate nitrate-nitrite-NO pathway. This is why many quality formulas include both citrulline and beetroot, to cover both angles.

I train Brazilian Jiu-Jitsu about four times a week. Sparring, or 'rolling' is not like lifting weights. There is no set rest between rounds, really. You are either moving, framing, breathing through pressure, or trying to recover while someone is crushing your diaphragm. Stamina is important.

About forty-five minutes before I step on the mats, I mix a scoop of Total Nitric Oxide with water. I happen to pair it with Shroom TECH Sport, Onnit's cordyceps-based pre-workout, which I will come back to in a moment.

The difference is not dramatic in a Hollywood way. I do not suddenly become a world class athlete. What I do notice is this: I can maintain a higher pace for longer before my grip fades and my breathing turns ragged. My recovery between rolls feels shorter. I am less likely to hit that wall in the fifth round where my limbs feel heavy and my decisions slow down. I still get tired. I still get tapped. But the gas tank feels bigger, and that is what matters when you are trying to stay technical late into open mat.

Is it placebo? I don't think so. The blood flow mechanism is well documented. But the real tell...? - the times I don't take it, are the times I notice it! I have forgotten to take it enough times to notice the difference when it is not there. Because there's no 'stimulant' aspect to it, you only really notice when you're gassing early because you left it in work, or whatever and that is enough for me to keep it in the stack.

Personal experience is useful, but alas, it is not proof. Here is what the peer-reviewed literature actually shows.

A 2013 meta-analysis in the Journal of Nutrition pooled data from sixteen randomised controlled trials on inorganic nitrate and beetroot juice. The results showed a significant reduction in systolic blood pressure of 4.4 mmHg compared with placebo, with larger nitrate doses producing larger effects.

More recently, a 2022 systematic review in Frontiers in Nutrition focused on adults with hypertension. Across seven trials, beetroot juice-derived nitrate reduced systolic blood pressure by a mean of 4.95 mmHg. The authors noted the effect held steady over time with no sign of tolerance.

Beetroot juice has been studied heavily for athletic performance. A 2016 systematic review in the Journal of the International Society of Sports Nutrition analysed twenty-three studies and concluded that beetroot juice may improve cardiorespiratory endurance by increasing efficiency, improving time to exhaustion, and supporting performance at anaerobic threshold intensities.

The mechanism is a reduced oxygen cost of exercise. Your body uses less oxygen to maintain the same output, which delays fatigue. That maps pretty well onto what I feel on the mats.

L-citrulline has been studied for post-exercise recovery. A 2020 systematic review and meta-analysis in BMC Sports Science, Medicine and Rehabilitation included thirteen studies and found that citrulline supplementation significantly reduced muscle soreness at twenty-four and forty-eight hours post-exercise, as well as reducing ratings of perceived exertion during training. The most common effective dose was eight grams of citrulline malate.

For BJJ, this matters. After a heavy session, my forearms, hips, and lower back usually feel it. Anything that takes the edge off DOMS without me having to change my training schedule is worth knowing about.

Because nitric oxide is the primary signalling molecule for smooth muscle relaxation in penile tissue, it plays a central role in erectile function. This is the same mechanism that prescription ED medications target.

A 2019 systematic review and meta-analysis in the Journal of Sexual Medicine evaluated ten randomised controlled trials with 540 men. L-arginine supplementation at doses between 1,500 mg and 5,000 mg significantly improved erectile function compared with placebo, with an odds ratio of 3.37. The researchers concluded arginine supplements may be recommended for men with mild to moderate ED.

A 2023 meta-analysis in Frontiers in Endocrinology found that the combination of L-arginine and Pycnogenol produced significant improvements across multiple domains of sexual function, including erectile function and overall satisfaction.

I mentioned earlier that I take Total Nitric Oxide alongside Shroom TECH Sport. Here is why that combination works for me.

Nitric oxide handles the blood flow side. It gets oxygen and nutrients where they need to go. Cordyceps, the mushroom extract in Shroom TECH Sport, handles the cellular energy side. It is thought to support ATP production and oxygen utilisation at the cellular level, which complements the circulatory benefits of NO without overlapping.

Together, they cover two different bottlenecks in stamina: delivery and utilisation. I take the NO for the pump and the oxygen delivery. I take the cordyceps for the clean, non-caffeinated energy and endurance. If you are sensitive to stimulants but still want a pre-training stack, this pairing is worth experimenting with. Neither product relies on caffeine, so you are not jittery, and you are not crashing halfway through drilling.

Nitric oxide supplements do not contain NO gas. They provide ingredients your body uses to produce more of it. The main players are:

L-Citrulline: Converted to L-arginine in the kidneys, which then feeds nitric oxide production. Research shows citrulline raises plasma arginine levels more effectively than arginine supplementation itself, because oral arginine is largely broken down in the gut and liver before it reaches circulation.

Beetroot: Rich in dietary nitrates, converted to nitric oxide via the nitrate-nitrite-NO pathway. This is independent of the arginine pathway, so beetroot and citrulline complement each other well.

L-Arginine: The direct precursor to nitric oxide. Well studied but less efficient than citrulline at raising circulating arginine levels when taken orally.

Vitamin C: Included in some formulas to help protect nitric oxide from oxidative breakdown, supporting bioavailable NO levels during exercise.

Nitric oxide supplements are generally well tolerated, but they are not for everyone.

Because NO widens blood vessels, it can lower blood pressure. If you are already on medication that does the same, the combined effect could be too strong. Check with your GP before starting.

Most nitric oxide supplements come as a powder mixed with water, taken thirty to sixty minutes before exercise. I take mine about forty-five minutes before BJJ, which seems to be the sweet spot for feeling it kick in right as we start drilling.

Follow the dosage on the label and do not exceed the recommended amount. As with any supplement, it works best alongside consistent training, adequate sleep, and a diet that includes nitrate-rich whole foods like beets, spinach, and arugula.

Nitric oxide is a real molecule with real effects on blood flow, exercise performance, and vascular health. The research supports modest but meaningful benefits for blood pressure, endurance, muscle soreness, and erectile function.

It is not a magic powder. It will not turn you into a world champion overnight. But if you want to support your body's own nitric oxide production with ingredients that have actual science behind them, a quality nitric oxide supplement is a practical place to start. If you train in a sport where stamina under pressure matters, and you want to pair it with something for cellular energy, try stacking it with a cordyceps-based pre-workout like Shroom TECH Sport. That is what I do, and it works for me.

What is nitric oxide? Nitric oxide is a signalling molecule produced naturally in your body, mainly in the lining of blood vessels. Its main role is vasodilation, which means relaxing and widening blood vessels to improve blood flow.

Do nitric oxide supplements actually contain nitric oxide? No. They contain ingredients your body uses to make nitric oxide, such as L-citrulline, L-arginine, and beetroot-derived nitrates.

What is the difference between L-citrulline and L-arginine? L-citrulline is converted into L-arginine in the kidneys. Research suggests citrulline is more effective at raising circulating arginine levels than arginine itself, because much of oral arginine is broken down before it reaches the bloodstream.

Can nitric oxide supplements lower blood pressure? Some research suggests beetroot juice and nitrate supplementation may reduce systolic blood pressure modestly. If you are on blood pressure medication, consult your doctor before using NO supplements.

Do nitric oxide supplements improve gym performance? The evidence is mixed but promising. Beetroot juice has been shown to improve time to exhaustion and reduce the oxygen cost of exercise in some studies. Citrulline may reduce muscle soreness and perceived exertion. Benefits appear more consistent in recreational and moderately trained individuals.

Are there side effects? Most people tolerate nitric oxide supplements well. Some may experience mild stomach discomfort. Because these supplements can lower blood pressure, avoid them if you have hypotension or are on blood pressure medication unless cleared by your doctor.

Can women take nitric oxide supplements? Yes. The blood flow and exercise performance mechanisms apply regardless of sex. However, pregnant or breastfeeding women should avoid NO supplements unless advised otherwise by a healthcare professional.

Why do you pair nitric oxide with cordyceps? I pair them because they address different bottlenecks. Nitric oxide improves blood flow and oxygen delivery. Cordyceps supports cellular energy and ATP production. Together they cover delivery and utilisation without relying on caffeine.