In the world of sports and competitive bodybuilding, athletes constantly search for any type of nutritional supplement that can give them an edge over the competition and improve performance. Among popular supplements in the sports nutrition world are L-arginine, also known as arginine, and creatine. These supplements function differently in your body, and creatine is far more likely to produce increased muscle growth than arginine is.

Proposed Functions

Even if arginine and creatine are both effective at building muscle, their proposed benefits are significantly different. Registered dietitian Ellen Coleman explains that arginine’s purported benefit is an increase in the amount of nitric oxide in your blood. Nitric oxide is a known vasodilator, meaning that increased nitric oxide in your blood potentially means more oxygen and muscle building amino acids will be delivered to your muscles. Creatine does not directly affect muscle growth but rather increases the amount of phosphocreatine you have stored in your muscles. Phosphocreatine functions as a precursor to the energy source ATP, which is the primary form of energy your muscles use when you are lifting weights. This means you can potentially exercise at a higher intensity for longer to build more muscle.

Arginine Research

There is little evidence to support arginine supplements as a muscle-building aid. While it can increase nitric oxide levels for people with heart conditions such as congestive heart failure and angina, few studies have shown a benefit for strength training. A 2006 trial of arginine for muscle building in “Nutrition” did show resistance-trained men could increase their bench press significantly with an arginine supplement. However, well-designed research studies, such as a 2011 trial appearing in the “Journal of Strength and Conditioning Research,” have found no benefit to arginine supplementation.

Creatine Research

Unlike arginine, researchers have extensively studied creatine as a muscle-building aid. The American College of Sports Medicine states that creatine can increase your muscle mass. However, results can vary considerably from one individual to the next. The primary influencing factor appears to be the amount of creatine you have stored in your muscles before you begin taking the supplement. If you have low muscle creatine stores, such as those present in vegetarians, you will likely experience the most benefit from a creatine supplement.

The Arginine Paradox

One potential reason that arginine does not work as well as creatine for building muscle is that your body regulates the amount of arginine you can maintain at one time. University of Milan nutrition professor Francesco Dioguardi refers to this as “the arginine paradox.” The more arginine you put into your body beyond your daily need, the more your body releases an enzyme to break down arginine. This may lead to a decrease in the nitric oxide in your body, and the enzyme perpetually breaks down arginine before more nitric oxide can be produced.