Does L-Arginine Actually Increase Size?
Explore the science behind L-arginine and claims of increased size. Understand its role in blood flow and how this affects function versus permanent physical change.
L-arginine is an amino acid, one of the building blocks of protein that the body uses for numerous functions. It is considered semi-essential, meaning the body can typically produce enough on its own, but sometimes requires more from dietary sources, especially during periods of growth or injury. Found in protein-rich foods like meat, fish, dairy, and nuts, L-arginine has gained widespread attention for claims related to increasing size.
The Role of L-Arginine in the Body
The primary function of L-arginine relevant to discussions about size is its role as a precursor to nitric oxide (NO). In the body, an enzyme converts L-arginine into this important signaling molecule. One of the most well-documented effects of nitric oxide is vasodilation, the widening of blood vessels as their smooth muscles relax. This improved circulation is central to how L-arginine influences various bodily functions, from cardiovascular health to exercise performance.
L-Arginine and Penile Health
Scientific evidence does not support the claim that L-arginine can permanently increase penis size. The size of the penis is determined by genetics and development, and supplements do not change this. What the science does suggest is a benefit related to erectile function, which can be perceived as a size increase.
When nitric oxide promotes vasodilation, it relaxes the blood vessels within the penis, allowing the spongy erectile tissues, the corpora cavernosa, to fill with blood more effectively. This leads to a firmer and more sustained erection. For some individuals, particularly those with circulatory issues or mild to moderate erectile dysfunction (ED), this enhanced blood flow can help them achieve their maximum potential erection size.
This isn’t a permanent size increase but rather the penis reaching its full capacity during arousal, which may appear larger or fuller than erections experienced previously. Some studies have shown that L-arginine, sometimes in combination with other supplements like Pycnogenol, can improve erection quality in men with ED. However, for individuals with normal erectile function, the effects may be less noticeable.
L-Arginine for Muscle Growth and Exercise
Another common claim is that L-arginine can increase muscle size. The theory behind this is linked to the same mechanism of vasodilation. Increased blood flow during physical activity could theoretically enhance the delivery of oxygen and essential nutrients to working muscles. It could also help with the removal of metabolic waste products, like lactate, potentially delaying fatigue and improving recovery.
A 2020 review suggested L-arginine may have a positive effect on both aerobic and anaerobic exercise performance. Some studies indicate that athletes may be able to work out longer or with more intensity. One study on weightlifters found that supplementation improved their resistance to muscular fatigue, which could contribute to building more muscle over time.
However, the evidence that L-arginine supplementation directly leads to significant gains in muscle mass is mixed, with some research finding no considerable impact. While it may aid exercise performance, which indirectly supports muscle development, it is not a direct driver of muscle hypertrophy in the way that resistance training and adequate protein intake are.
Safety, Dosage, and Considerations
In clinical studies investigating erectile function, dosages typically range from 2.5 to 5 grams per day. The National Institutes of Health suggests that daily doses up to 9 grams are generally safe for short-term use, though the long-term effects are less understood. The most common side effects are gastrointestinal, including stomach pain, bloating, nausea, and diarrhea.
Due to its vasodilating properties, L-arginine can also cause a drop in blood pressure. People on blood-thinning medications or drugs for erectile dysfunction should consult a healthcare provider before use. Individuals with a history of heart attack are advised against using it due to mortality concerns, and those with a history of herpes should be aware that supplementation could trigger an outbreak.