In recent years, there is more discussion on the importance of endothelial health, or the health of the cells that line our cardiovascular system. Endothelial dysfunction is a known risk factor for cardiovascular disease, and in fact may play a much more central role than things like cholesterol alone. One of the most important molecules regulating the health of the endothelium is nitric oxide.
The Importance of Nitric Oxide
Nitric oxide is a soluble (meaning it can dissolve in water) gas floating throughout our blood stream. It is continuously released from the endothelium for a number of reasons, the most important of which is “vasodilation”, or the relaxing of our blood vessels. We want our blood vessels to remain nice and open so blood can flow optimally and oxygenate all of our tissues, so that blood pressure remains at a healthy level, and also to lower the risk of a clotting event.
Because nitric oxide has been recognized as such a critical molecule, researchers have tried to figure out if there are ways we can boost our levels of nitric oxide, and if boosting those levels is associated with health benefits. (Interesting side note, breathing through your nose creates more nitric oxide in the body than mouth breathing!) There are two main pathways the body uses in creating more nitric oxide. The primary pathway is converting the amino acid L-arginine into nitric oxide via enzymes known as nitric oxide synthases. The other is the conversion of “nitrate” (found in the body in small amounts, but also the diet) into nitric oxide. As you might imagine, L-arginine and nitrates, the precursors to nitric oxide, are among the supplements that have been researched to help boost nitric oxide. I’ll also discuss a third not yet mentioned, L-citrulline.
Nitrates in the Diet
Nitrates in the diet can be found in highest concentration in beetroots. This is why many supplements marketed for nitric oxide support are primarily beetroot juice or concentrate. Nitrates are also found in leafy green vegetables and roots like radishes and turnips. As mentioned above, nitrates can be converted into nitric oxide which dilates the blood vessels and improves blood flow, among many other effects.
A quick detour: you may be aware that there has been some concern about cancer risk from nitrates. Those investigations have been concerning nitrites and nitrates specifically from food additives and processed meat, and even that data is a bit conflicting. The dietary nitrates found from vegetables, which also contain antioxidants and so many other beneficial compounds, are not thought to increase cancer risk; in fact they are thought to reduce it. That said, since we don’t yet understand all of the implications of supplementing with high amounts of nitrates in the form of beetroot (or similar plant extracts), I am a bit hesitant to recommend it as an ongoing, daily supplement.
Beetroot As A Supplement
Beetroot can make for a good targeted supplement to take occasionally before workouts or intense physical activity, though. A systematic review and meta-analysis in 2021 showed that beetroot can increase maximum power by about 5%. For people who are not regularly in the gym, this likely won’t matter too much, but for those looking for a little extra support to help them reach a new personal best, beetroot may be able to help. We have reason to believe that beetroot may boost nitric oxide for up to a few hours, based on a trial that showed exhaled nitric oxide levels were elevated significantly at 90 minutes after consumption, and in a few individuals up to three hours later.
L-Arginine and L-Citrulline
L-arginine and L-citrulline work a little bit differently in boosting nitric oxide. Like nitrate, L-arginine is also a direct precursor to nitric oxide, however it utilizes a different pathway. L-citrulline can be turned into L-arginine, and actually will increase L-arginine levels more than L-arginine itself, which is probably a bit counterintuitive. The reason for this is because much of the L-arginine you consume will be broken down before it gets to your bloodstream. L-citrulline also has the upside of being tolerated better than L-arginine, which for some people can cause gastrointestinal distress.
For those reasons, L-citrulline may be a superior supplement to L-arginine for boosting nitric oxide levels more consistently. The reality is that we don’t really have enough research to feel highly confident on the benefits of L-citrulline as compared to L-arginine (which has a lot more research). However, just as there is with L-arginine, there is data supporting benefits including exercise performance and recovery enhancements, improvements to erectile dysfunction, and blood pressure lowering. Because of the importance of nitric oxide across the body, it is also possible that supporting nitric oxide with these amino acids could offer some cardiovascular protection or even enhance immunity. Time will tell if the research indeed supports this.
But for now, nitric oxide supports like beetroot, L-arginine and L-citrulline appear to be safe supplements with low risk that can benefit circulatory health.