Nitric oxide is a signalling molecule that is formed by combining nitrogen and oxygen, it has “many pathological and physiological processes within the mammalian body” (1).
Nitric oxide supplements help improve blood flow, cognition and workout capacity. However you can’t simply take “nitric oxide”. Instead can take different supplements that can boost nitric oxide levels. Examples of supplements that can increase nitric oxide are; arginine, citrulline, cocoa extract, curcumin, DHEA, fish oil, l-carnitine.
The main function of nitric oxide is vasodilation of the blood vessels. It can help prevent cardiovascular disease, improve cognition, and improve recovery. There are many natural methods to increase nitric oxide production. Exercise is an excellent way to increase nitric oxide, as is laughter (believe it or not) (2, 3, 4).
A 2009 study found that laughter released beta-endorphins, they hypothesized that “such positive emotions lead to the direct release of nitric oxide and associated biological consequences” (5).
Eating foods that are high in nitrates is another way to increase nitric oxide, this is because nitrates can be broken down into nitric oxide in the gut (6).
Exposure to sunlight can increase nitric oxide production too (7).
Finally, if your body isn’t producing enough nitric oxide to meet your needs, you can increase production using exogenous nitric oxide in the form of supplements.
1Nitric oxide can improve exercise recovery, endurance and intensity. The number one reason why people take nitric oxide enhancing supplements is to improve their workout quality.
A number of studies have found that increasing nitric oxide can improve oxygen and nutrient delivery to the muscles, recovery from exercise, and tolerance to exercise intensity (8).
A 2008 study on postmenopausal women found that supplementing with l-arginine (a common nitric oxide boosting supplement) “increased maximal force in mechanographic analyses and may prevent a decline of muscle force in postmenopausal women” (9).
A study in the Chinese Journal of Physiology (2009) found that l-arginine supplementation led to an increase in glucose and insulin concentrations post workout (10).
Having elevated insulin levels can help improve muscle protein synthesis and therefore recovery from exercise.
The Journal of Applied Physiology looked into the effect of l-arginine on moderate and high-intensity exercise (11).
The study found that increasing nitric oxide production led to a reduction in the oxygen cost of moderate exercise, and enhanced high-intensity exercise tolerance. Meaning athletes could train at higher intensities.
Another study, from 1985 (but updated in 2010) found that nitrate supplementation (nitrate can be broken down into nitric oxide in the gut) reduced the cost of oxygen during a knee extensor exercise, and therefore “allowed high-intensity exercise to be tolerated for a greater period of time” (12).
A study in the American Journal of Physiology (2010) looked at the effect of dietary nitrate supplementation on moderate intensity exercise (13).
Again, this study found evidence that increased nitric oxide could reduce the energy cost of submaximal exercise, making low to medium intensity exercise easier to perform.
Another study (2011) in the Journal of Applied Physiology found that dietary nitrate supplementation reduced the oxygen cost of walking and running on a treadmill (14).
The study used beetroot juice which is a good source of nitrate, but it only tested 9 healthy, physically active males – which is quite a small number.
A study in 2011 looked at the effect of dietary nitrate supplementation on cycling time trial performance (15).
They found that beetroot juice improved cycling economy and boosting power output – which led to faster time trials.
A 2010 study in the Journal of Strength & Conditioning looked at the effects of arginine based supplements on physical working capacity in people who were fatigued (16).
The study found that there were significant increases in performance capacity in subjects who took arginine while there was no significant difference in the placebo group.
But not all studies have seen a difference, a 2009 study in the International Journal of Sport Nutrition & Exercise Metabolism found that dietary l-arginine intake did “not improve physiological parameters during exercise” (17).
A 2010 study found that l-arginine failed to improve physical performance (but it also failed to increase Nitric Oxide levels) (18).
They failed to find an increase in blood flow or any improvement in “acute upper body exercise performance”. Again, this may be down to a failure of the ingredients to increase nitric oxide rather than a failure of nitric oxide.
Richard Bloomer in 2010, looked at nitric oxide supplements in sport. He concluded that:
“Nitric oxide-stimulating dietary supplements are widely available and aggressively marketed to the sports/bodybuilding community. Unfortunately, these products have little direct scientific evidence for effect and depend largely on borrowed science related to research done on isolated and intensified dosing of certain ingredients, in particular l-arginine. This, coupled with paid endorsements from top athletes, and a bit of the placebo effect thrown in for good measure, have catapulted this class of supplement to the top of the bodybuilding world.” (20)
So not a fan then. But that doesn’t mean that nitric oxide boosting supplements are incapable of working, just that in 2010 there wasn’t enough evidence of nitric oxide boosters working.
What Bloomer says about most studies focussing on one ingredient that happens to increase nitric oxide rings true. Most of the studies include either l-arginine or l-carnitine.
Overall it’s difficult to say whether nitric oxide boosting supplements are effective at improving workouts. Often, they are paired with caffeine – which is an excellent pre-workout ingredient or creatine which is also very effective.
Being paired with two very powerful performance enhancers may hide the fact that the nitric oxide booster is ineffective.
Alternatively, nitric oxide boosters may indeed increase blood flow – provided the supplement is of good quality. There definitely is evidence that increased blood flow can help improve a workout and the recovery process.
Perhaps supplementing directly with l-arginine or l-citrulline would be more effective.
2Nitric oxide can improve cognition. There appears to be quite a lot of evidence that nitric oxide has a role in memory and cognition. A study on rats in the British Journal of Pharmacology (1995) found that inhibiting nitric oxide led to a reduction in performance of the radial arm maze task (a test of special learning in rats) (21).
If this is the case, then nitric oxide must help to improve memory and cognitive performance.
A 2011 study in the Indian Journal of Medical Research found that “nitric oxide activates the computational ability of the brain. These findings provide sufficient support to the report that l-arginine, the precursor and donor of nitric oxide may play a prominent role in the treatment of age-related degenerative diseases such as AD” (22).
In other words, nitric oxide boosting supplements may help to prevent alzheimer’s disease and similar degenerative diseases of the mind. According to David S. Geldmacher, writing in the Cleveland Clinic Journal of Medicine (23):
“Diabetes, hypertension, dyslipidemia, and obesity might lead to dementia in a process abetted by oxidative stress, endothelial dysfunction, insulin resistance, inflammation, adiposity, and subcortical vascular disease. All of these could be targets of intervention to prevent and treat dementia”
A study undertaken by Professor Ian Forsyth at the University of Leicester (2008) found that nitric oxide “can change the computational ability of the brain” (24).
3Nitric oxide can improve erections and help fight off erectile dysfunction.To get an erection, blood needs to flow into chambers of your penis called the corpus cavernosa. Once the chambers are filled with blood they can expand causing an erection.
The chambers are supplied via blood vessels, when these become damaged it can lead to erectile dysfunction. Nitric oxide can help prevent this by widening blood vessels, which in turn improves blood flow to the penis.
A study in 1992 by Burnett found that nitric oxide provides a crucial role in erectile function and it seems clear that nitric oxide supplementation could absolutely help somesufferers of erectile dysfunction (particularly any who suffer from obesity, diabetes etc) (25, 26).
4Nitric oxide supplements can help prevent cardiovascular disease. As mentioned above, nitric oxide has a powerful effect on blood flow which is what makes it so popular with gym goers. But this can also help to protect the cardiovascular system from disease.
A study in the Canadian Journal of Cardiology (2004) looked at the effect of nitric oxide on atherosclerosis, claiming that “New agents that specifically target the nitric oxide synthase pathway have been developed, and represent a new front on the war against heart disease”(27).
In 2011 a study was published in the Journal of Circulation Research found that increased nitric oxide (from exercise) can protect the heart from myocardial ischemia-reperfusion injury (28).
This demonstrates that increasing nitric oxide (albeit from exercise rather than supplementation) can have a protective effect on the heart.
A study in 2005 by Guix looked at “the physiology and pathophysiology of nitric oxide in the brain” and claimed that nitric oxide could play a protective role in the vascular system, and help regulate blood flow (29).
Because you can’t take nitric oxide directly as a supplement, it is pretty much impossible to get any side effects from it.
In the next section (recommended dosages) we look at the different supplement ingredients that can increase nitric oxide production (l-arginine, l-citrulline, cocoa extract, curcumin, DHEA, fish oil, garlic, l-carnitine).
Some of these ingredients may have side effects of their own when taken in high doses. But provided that you stick to the recommended dosage for each you should see no ill effects.
Nitric oxide is not taken directly as a supplement, instead, you need to take supplement ingredients that can increase nitric oxide production in the body. In this section, we will identify some of the evidence-based supplement ingredients that can increase nitric oxide, and provide the recommended dosage for each.
But this is not always the case, some studies failed to find any evidence of l-arginine increasing nitric oxide levels, despite plasma arginine being required for nitric oxide to be formed in the body (32).
The recommended dosage for l-arginine is 3-6g
L-citrulline – A good supplement for increasing nitric oxide levels. A 2010 study found that L-Citrulline-Malate led to an increase in nitrate (33).
The recommended dosage for L-citrulline is 3 x 1,000mg per day
Cocoa extract – Potentially a good supplement for boosting nitric oxide levels in smokers, but not enough evidence at this moment in time (34).
The recommended dosage for cocoa extract is 500-1,000mg
Curcumin – The active ingredient in turmeric that a lot of people have got excited about recently. A 2012 study noticed a significant increase in nitric oxide when subjects took 80mg of curcumin, but there is little evidence outside of this study (35).
The recommended dosage for curcumin is 80-500mg
DHEA – A hormone that can be converted to either testosterone or estrogen, DHEA is often seen as an anti-aging supplement. A 2006 study found that 50mg of DHEA led to increased levels of a biomarker for nitric oxide (it is almost impossible to measure nitric oxide levels specifically) (36).
The recommended dosage is 25-50mg
Fish oil – A study in 2010 found that fish oil supplementation increased nitric oxide levels, but also found that it increased oxidative stress from exercise (37).
The recommended dosage for fish oil is 250mg
Garlic – A 2007 study found that raw garlic could increase nitric oxide levels by 224% for 2-4 hours after ingestion (38). There is no recommended dosage.
L-carnitine – A study published in the International Journal of Vitamin & Nutrition Research (2009) found that 3g of L-Carnitine was able to significantly increase nitric oxide levels (39).
The recommended dosage is 500-2,000mg (however for an increase in nitric oxide you would need 3,000mg).
Is nitric oxide good for the body? Yes it its. Nitric oxide expands the blood vessels, increasing blood flow and decreasing plaque growth and blood clotting.
Can nitric oxide supplements help with erectile dysfunction? Yes they can. Since they promote blood-flow, erections will be stronger, harder and easier to maintain.
Are nitric oxide supplements safe for your heart? There is no evidence to support any long term damage of using nitric oxide supplements. As such, they are categorized as completely safe and even healthy supplements.
Are nitric oxide supplements safe to take with high blood pressure? Yes and since they help expand the blood vessels, they can even help lower blood pressure.
Which foods help produce more nitric oxide? These foods include: Dark chocolate, citrus, pomegranate, walnuts, spinach, watermelon and beets.
Are there any side effects of nitric oxide supplements? As long as you are taking recommended dosages, there will be no side effects. If you exceed the dosages dramatically, you could create low blood pressure temporarily. It’ll subside.
How do nitric oxide products work? Nitric oxide supplements don’t actually provide nitric oxide, which is a gas, but generally contain nitric oxide. precursors which can, increase nitric oxide and deliver all the aforementioned benefits.
Increasing nitric oxide levels through exercise and supplementation can have a number of benefits. Improved workouts is a great example of that. The increased blood flow allows for more work to be done, less fatigue to accumulate, and better recovery afterwards. Combining nitric oxide boosting ingredients with other common pre-workout ingredients (caffeine, creatine etc) has become very popular, and you will see some excellent results from this.
But nitric oxide is not just useful for exercise, it can have benefits for your mental cognitive abilities. It’s role in helping prevent neurological disorders such as Alzheimer’s Disease could become vital in the future when more research is undertaken.
Often not a popular discussion in polite society, the effect of nitric oxide boosting supplements on erectile dysfunction – particularly In those suffering from metabolic diseases such as obesity, is potentially game changing. Likewise, the cardio protective effect of nitric oxide (particularly when paired with exercise) could prove to be life changing.
As with most popular supplements, it is always better to boost your levels of nitric oxide through exercise and diet. If you are doing this then there is no need, nor any real benefit to supplementation, if your nitric oxide levels are low then supplementation could be an effective short-term solution. Combining supplementation with gentle exercise and an increase in nitrate rich foods would be even better.