Just Say NO: A Look at Nitric Oxide Supplements
NPB digs into the confusing world of these popular ergogenic aids.
Nitric oxide—or NO—sups are one of the most common pre-workout products out there. They’re also considerably more confusing than other super-popular ergogenic boosters like caffeine, so let’s spend a hot minute untangling them.
What does nitric oxide do for my workout?
In the body, NO functions as a signaling molecule, which means it binds to other molecules and tells them what to do. It signals a lot of different cell processes but for our purposes, it functions as a vasodilator. This means it signals vascular smooth muscle (the walls of your veins) to relax, so that blood can flow better. More oxygen and other nutrients get to your muscles—and they perform better.
Wait, isn’t nitric oxide the stuff dentists give patients that makes them laugh?
You’re thinking of nitrous oxide (N2O), which you might know as laughing gas. That’s a different thing. For what it’s worth, a study in the European Journal of Applied Physiology showed that sucking in N2O did nothing from aerobic performance, so if you’re tempted by the idea of pre-race poppers, just say NO instead. (See what I did there?)
But I thought nitric oxide was toxic!
You are correct in the sense that NO gas is a toxic, air polluting by-product of tobacco smoke and car exhaust. Don’t stress though, because the NO that naturally occurs inside your body is perfectly healthy. I know that seems counterintuitive and I double-checked this fact a dozen times, but it’s true.
In fact, there’s no actual NO in NO supplements, since NO is a gas. A Swedish company briefly experimented with selling actual NO in pill form, but it didn’t pan out given the toxic issues. Also, the capsules tended to float away when customers opened the bottles.
(I completely made that up. While it’s true that NO is a toxic gas, the Swedish pill part never happened. I mean, come on, everyone knows that nitric oxide is heavier than oxygen, so the pills wouldn’t float!)
So, what’s in nitric oxide sups then?
They contain precursors to NO—meaning they contain stuff that the body converts into NO.
NO is made by a combo of the amino acid arginine plus nitrate. Therefore, you’ll probably find one of these things in your NO supplement:
L-citrulline, which is another amino acid that converts to arginine
Sodium or potassium nitrate
A food concentrate that naturally contains nitrates, typically beetroot extract
But do nitric oxide sups work?
The problem with consuming arginine is that most of it gets broken down during digestion and in the liver before it gets to the bloodstream. Citrulline, on the other hand, isn’t broken down and converts to arginine in walls of your veins (among other places). A 1985 study in the Journal of Applied Physiology compared arginine and citrulline supplementation in cyclists. Citrulline worked better. Here’s a 2022 study from the journal Beverages backing that up.
The other route you can take is nitrates. Sodium or potassium nitrate, or “nitrate salts” are cheap and synthetic. They’re also used to cure meat. Beetroot extract costs more, but it’s also a more natural way to go. As a bonus, you get the other nutrients found in beets, like calcium, iron, and potassium.
According to this 2020 meta-analysis of 100 studies in Medicine & Science in Sports & Exercise, nitrate supplementation seems to have a positive ergogenic effect on “young, healthy men and women.” Although, there are also studies suggesting it doesn’t work.
Of course, there’s also the obvious twofer approach—why not take both citrulline and nitrates? You’ll find sups containing this cocktail—along with research supporting it, such as this 2019 study in the journal Aging suggesting the benefit of chronic use of the combo for older exercisers.
There’s also a cool 2022 study in Nutrients on amateur triathletes (my people!) that split participants into four groups: a citrulline group, a beetroot extract group, a citrulline plus beetroot extract group, and a no-NO control group. The combo group showed the most improvement in performance associated with aerobic power, including an increased estimated VO2 max.
For those keeping score, these participants were given 3 gram of citrulline and 2.1 grams of beetroot extract daily for 9 weeks.
Note that the first study provided nitrites in the form of salad and the triathlete study used beetroot extract. In other words, you don’t necessarily need supplements to boost your internal NO.
That said, supplements allow you to ingest clinically studied amounts and I, personally, am not thrilled about eating a Seinfeldian Big Salad right before doing sprint drills, but that shouldn’t stop you from filling your diet with NO-boosting foods.
For citrulline, good sources include squash, cucumber, cucumber, and watermelon—basically, if it’s a fruit or veggie that completely takes over your garden, it’s probably got citrulline in it.
For nitrates, the big winner is beetroot (or just “beets” as we say in ‘Merica). Leafy greens like kale, chard, and spinach are good too.
In my experience, you tend to know if NO sups are working for you, so if you’re curious, try them out for a couple months. They’re not especially expensive—and who knows?
If you do, drop us a line here at NPB and tell us how it goes!
Just a reminder, I’ll be appearing in the Consequence of Habit Virtual Meeting tomorrow (Friday).
It’s a roundtable event, so please sign up here and come equipped to participate!
Also note that it’s 7pm EST—that means 4pm PST!
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