L-arginine is an amino acid that is a core part of the body’s nitric oxide synthesis pathway. Nitric oxide controls blood flow, which means L-arginine has a huge range of applications: improving workout performance, increasing endurance, boosting sexual performance, and even enhancing long-term health.
Want to incorporate L-arginine into your supplement stack? Here’s what you can expect.
1. L-arginine can improve muscle gains and help shed fat
A 2009 study (1) shows that l-arginine can lead to muscle growth and fat loss.
The study was experimented on 24 pigs over a 60 day period found tremendous results in overall weight loss and muscle development.
Another study conducted by Zajac et.al (2) found that increases in l-arginine leads to an increase in growth hormone levels.
This has important results for bodybuilders and trainers who train to burn fat and increase muscle size.
2. L-arginine decreases blood pressure
The actual mechanism L-arginine uses to improve blood flow is vasodilation, which can help lead to healthier blood pressure levels.
This finding was confirmed in a meta-analysis of several studies, showing that L-arginine supplementation improves both systolic and diastolic blood pressure (3).
3. L-arginine can improve erectile function
Because L-arginine improves blood flow, it can improve erectile dysfunction in men (4). Like other compounds in male enhancement pills, the increased blood flow caused via elevated nitric oxide levels improves both erectile function and strength.
4. L-arginine can help repair your body after tough workouts
A study conducted by researchers at the University of Texas at Austin suggests that athletes could take advantage of L-arginine for recovery (6).
The study involved twelve trained cyclists who completed hard training rides, then refueled with either a carb-only sports drink or a supplement that provided both carbohydrates and L-arginine.
The researchers found that when the cyclists refueled with a supplement that provided L-arginine in addition to carbohydrates, their rate of carb oxidation decreased following exercise, which they interpreted as a sign that more carbohydrates were being absorbed into the muscles as opposed to just being burned for energy.
These results indicate that recovery after a tough workout can be boosted if you consume L-arginine in addition to carbohydrates—your muscles can take better advantage of the available fuel in your system to replenish your muscle glycogen stores.
5. L-arginine can improve both aerobic and anaerobic performance
A meta-analysis of 15 different studies on L-arginine supplementation and sports performance concluded that supplementing with L-arginine for several weeks can significantly improve performance, both in short, high-intensity exercise bouts (like sprints and HIIT training), as well as longer endurance-based aerobic activities like running and cycling (7).
The review emphasized the effects of L-arginine on the body’s energy generation during exercise, hypothesizing that L-arginine boosts the body’s ability to generate both aerobic and anaerobic energy.
L-arginine side effects
L-arginine can cause minor GI issues. Some of these side effects are nausea, diarrhea, and weakness in the body.
The Mayo Clinic notes that L-arginine can also cause headaches, bloating, and, rarely, allergic responses and airway inflammation in people who have asthma (6).
You shouldn’t take L-arginine if you already have heart disease. Some studies suggest that people with heart disease could have an increased risk of death if they take L-arginine (7).
Most research uses 2-10 grams per day. L-arginine doses in the scientific literature typically range from three to eight grams of L-arginine per day.
The higher end of the dosage range is typically reserved for clinical trials on people with heart disease or hypertension, while studies on sports and athletes in training use more middle-of-the-road doses, around five grams per day.
One review recommended 2 grams per day for aerobic performance, but up to 10-12 grams per day for anaerobic performance (7).
Some studies base dosage on body mass. Some more sophisticated studies prescribe dosages based on body mass: a typical amount might be 0.08 grams of arginine per kg of body mass.
So, an 80 kg athlete (176 pounds) would take 6.4 grams of L-arginine per day. This helps control for the fact that larger people have much more body mass and blood volume, so the same dosage of L-arginine will affect them to a lesser extent than a smaller person.
It’s not clear whether to take L-arginine all at once or space it out throughout the day. The research is less clear on how L-arginine should be spaced out throughout the day. Some studies use several divided doses, at different times during the day, but some have also had success with a single large dose of L-arginine all at once.
For recovery, take L-arginine as soon as possible after your workout. One thing we do know is that if you are using L-arginine to boost recovery after a tough training session or competition, you want to take L-arginine alongside one gram of carbohydrates per kilogram of body mass, and consume it as soon as possible finishing your workout.
This is the best way to optimize post-workout muscle glycogen recovery using L-arginine.
L-arginine benefits FAQ
Q: What foods are rich in L-arginine?
A: As a naturally occurring amino acid, L-arginine can be found in a wide range of foods that are rich in high-quality protein.
Some particularly good sources of L-arginine include pork loin, turkey breast, peanuts, pumpkin seeds, many different kinds of dairy, and surprisingly, even spirulina.
A diet high in these foods can naturally increase your body’s levels of L-arginine without the need of a supplement. Powder or capsule-based L-arginine, on the other hand, is a great addition to a protein shake or a smoothie if you want to add some more L-arginine to meals that would otherwise be devoid of it.
Q: What does L-arginine do for your sexual health?
A: Since L-arginine plays an important role in the synthesis of nitric oxide, it can be a helpful supplement for men who have erectile dysfunction.
Since men’s ability to get and sustain an erection is dependent on their ability to maintain blood flow, low levels of nitric oxide have been linked to erectile dysfunction in men, and L-arginine supplementation appears to help these men.
Interestingly, some research has suggested that women may also benefit from multi-ingredient supplements designed to boost L-arginine levels, but the research on this subject is not definitive (8).
Q: How can you increase nitric oxide without L-arginine?
A: If you want to stimulate your body to produce nitric oxide without using an L-arginine supplement, you have two good options.
The first is to take a supplement that provides other compounds used alongside L-arginine for nitric oxide synthesis. A good example of another compound related to the same nitric oxide production pathway is citrulline.
Alternatively, you can try stimulating nitric oxide production through a different pathway entirely. The best way to do this is with beetroot juice or a beet supplement, which also increases nitric oxide production through a completely different molecular pathway.
The end result is the same, though: better blood supply thanks to vasodilation induced by nitric oxide.
Q: Can L-arginine help with erectile dysfunction (ED)?
A: L-arginine is a common ingredient in male enhancement pills and other sexual wellness supplements for men because of its ability to increase nitric oxide production.
One review article points out that both erectile dysfunction and heart disease share many of the same risk factors: obesity, smoking, and high blood pressure, to draw just a few examples (9).
All of these risk factors modulate your body’s ability to regulate blood vessels using nitric oxide, which suggests that L-arginine, which increases nitric oxide production, could assist with erectile dysfunction.
A 1999 study confirmed this hypothesis, demonstrating that men with erectile dysfunction who had low levels of nitric oxide production reported substantial improvements in sexual function after taking an L-arginine supplement (10).
However, this study did note that not all cases of erectile dysfunction can be attributed to low nitric oxide levels, so while L-arginine may certainly help, it’s not going to be the solution for everyone.
Related: Our best L-arginine picks
L-arginine is a super-versatile amino acid that plays a key role in the synthesis of nitric oxide. The blood flow benefits from higher nitric oxide levels are what give L-arginine its broad range of applications, from boosting athletic performance to enhancing erectile function.
Some research has studies L-arginine alone and found benefits, while other experiments suggest it’s best-suited in combination with other compounds that play a role in nitric oxide synthesis, like citrulline.
L-arginine’s powerful effects on nitric oxide make it a great supplement to have at your disposal, whether your goals are long-term health, better sexual function, or PRs at the gym.