Bodybuilding supplements are popular, but they are not necessarily effective, safe, or worth the cost. L-arginine is a popular choice because of claims it can stimulate muscle growth. It also seems safe since it is an amino acid already in the diet.
Whether L-arginine is a worthwhile supplement is still up for debate. There are some benefits for training and performance, but the muscle-building claims may be overblown. Get the facts before trying this supplement or talking with your clients about it.
L-arginine is a conditional, or semi-essential, amino acid, a building block of protein. Essential amino acids are those our body cannot manufacture. We need to get these in our diets. L-arginine is conditional because the body can make it, but you need it in the diet under certain conditions: infancy, pregnancy, critical illness, or serious injury.
L-arginine is important in the body in several ways, not just as a component of proteins:
Arginine is needed for the production of nitric oxide (NO), which regulates blood flow, communication between cells, and other processes.
It is also a precursor for making other amino acids: creatine, proline, and glutamate.
Arginine is important in the production of T-cells, the white blood cells crucial to the body's immune response.
Arginine has essential functions in the body. If you become deficient, the consequences are serious, including disruptions to organ function and cell operations. A person only develops a deficiency in unusual circumstances, such as physical trauma or severe illness. The body can make arginine from the amino acid citrulline and from breaking down proteins. It's also easy to get from protein-rich foods.
You'll see supplement companies and some bodybuilding enthusiasts plug L-arginine supplements for building muscle, but the actual evidence proving it works is limited. In fact, a lot of the research fails to find any significant impact when added to regular strength training.
Some of the functions of L-arginine in the body have led to the idea that it can act as a muscle-building supplement. Perhaps most important is the connection to NO. Nitric oxide is essential for vasodilation, the relaxing and opening up of blood vessels.
This action increases blood flow. More blood flow to muscles can certainly have some benefits, possibly stimulating new growth by carrying in more oxygen and nutrients. Additional blood flow certainly benefits recovery, but it may not be adequate to make a difference in building muscle tissue.
L-arginine is a precursor to creatine, one of the most used performance supplements and another reason athletes and lifters may turn to arginine as a supplement. Studies have proven again and again that creatine is a useful supplement for athletic performance. It increases the capacity to exercise and build lean body mass in trained individuals. Because L-arginine is necessary to make creatine in the body, it follows that it may be a beneficial supplement for muscle building.
There is also a connection between L-arginine and hormones. Some people have hypothesized that it could stimulate the body's production of human growth hormone. Growth hormone is important for repairing, maintaining, and building muscle tissue. More of it in the body supports the growth of new muscle tissue. If L-arginine stimulates growth hormone, it could be used to build muscle mass.
Building muscle doesn't have to be complicated. The basics of building muscle, along with hard work and dedication, are all you really need.
Unfortunately, the evidence that L-arginine supplements actually increase muscle mass is not convincing. Research indicates that supplementing with specific amino acids, including arginine, does not increase muscle mass any more than training alone. Supplementation in the study also had no effect on muscle strength.
Some studies show that L-arginine supplements can stimulate an increase in growth hormone. However, this increase is less than what you get from exercise alone. In other words, your body will secrete more growth hormone when you exercise than when you supplement with L-arginine while exercising.
A review of several studies of the use of arginine found conflicting and poor evidence for its ability to stimulate muscle growth. One study looked at weightlifters and found that eight grams of arginine a day had no impact on their body composition or muscle function.
In another study, untrained men given arginine did have improved resistance to muscular fatigue. They could work out longer, which ultimately could help build more muscle. There was no control or placebo group with this study, however, which means the results are questionable.
Studies that did involve a placebo and control group found that people with heart conditions, such as congestive heart failure, benefitted from arginine supplementation. The supplement increased their exercise capacity.
The bottom line is that there is scant evidence to show that arginine as a supplement will build muscle any better than just working hard in the gym.
The current consensus on using L-arginine as a supplement to build muscle is that it is likely not effective. However, arginine does have other benefits and is used in other ways, including athletic performance.
Because of the connection to nitric oxide and increased blood flow, researchers have looked at L-arginine supplementation in sports performance and endurance. A study of 56 soccer players did show improved performance in a group that took two grams of L-arginine every day for more than a month.
Smaller studies have shown that athletes can work out longer when supplemented with L-arginine. On the other hand, some research has found no effect. The results are promising but mixed.
What is more certain is that L-arginine supplements benefit people with high blood pressure. This is due to nitric oxide, which relaxes blood vessels. A review of seven studies found that L-arginine is effective at lowering both systolic and diastolic blood pressure in adults who have high blood pressure.
Could supplementing with amino acids aid weight loss? The answer is maybe, but of course it's more complicated than that. Check out this ISSA post on amino acids to get more details.
The body quickly metabolizes L-arginine that you consume. This means that when you supplement this amino acid, much of it metabolizes before it can get into circulation in the bloodstream. Another amino acid may actually be better at increasing levels of arginine.
L-citrulline is the precursor amino acid to L-arginine. It is a non-essential amino acid that converts to L-arginine in the body. A supplement of citrulline will metabolize into arginine. Studies show that a citrulline supplement actually increases arginine levels more effectively than an arginine supplement and that it can provide similar benefits.
If you're interested in arginine supplementation to build muscle mass, consider trying citrulline. Alternatively, and because research results are often mixed, try a combination of the two.
L-arginine supplements are considered to be mostly safe. Even in higher doses, it is safe for most people. With very high doses, you may experience some nausea, diarrhea, or headaches. High amounts of arginine may be problematic in people with certain health conditions, especially those of the liver and kidneys.
Always talk to your doctor before trying any kind of dietary supplement. There may be risks specific to you. For instance, L-arginine can interact with blood pressure medications and others. It may also interact with certain herbal supplements.
Supplements for strength training can be contentious. Companies that sell them make a lot of claims that are not always true. It's important to do the research and learn more about these products before trying them and before speaking with clients on their value and safety.
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