Updated: May 5, 2020
Dear Dr. K, A lot of products are promising increased nitric oxide blood levels. What is it and what does it do?
Nitric oxide (NO) is the fuel that feeds the fire of your erection. NO is a simple molecule-one atom of nitrogen and one atom of oxygen (not to be confused with nitrous oxide- “laughing gas.”) NO is produced by the cells that line the walls of the blood vessels of your body. These cells, called endothelium, form the slick inner lining that keeps blood cells from sticking and forming clots. Think of them as a Teflon coating for your arteries. When stimulated by impulses from the parasympathetic nervous system, the endothelial cells release NO into the adjacent smooth muscle cells in the vessel wall. The NO causes the muscles to relax which opens up the vessel, increasing bloodflow.
The NO produced is quickly broken down in the cells by an enzyme called phosphodiesterase (PDE5) so it does not last long. Medications such as Viagra and Cialis block the actions of PDE5, allowing NO to hang around longer which increases the duration of your erection. (These medications were originally designed to treat high blood pressure, but had an unforeseen benefit in their test subjects--better erections. And the researcher, knowing they had a golden opportunity at hand, quickly changed the emphasis of their work.)
Two naturally occurring amino acids can boost NO levels in the blood. L-arginine is one of these and is available as a supplement. In the blood L-arginine is metabolized to NO and increases the level of NO available to your cells. This supplement is popular with weightlifters and bodybuilders because it allows more blood and oxygen to flow to the muscles causing “the pump” that that they want to get during their workouts. The absorption of L-arginine is partially blocked by a bacteria in the gut, so only a portion of the supplement makes it to the penis.
L-citrulline is another amino acid that is metabolized to NO. It is better absorbed in the gut and not degraded by the liver. It is converted to L-arginine in the kidneys. Thus it is able to deliver higher levels of L-arginine to the penis. When used in combination with L-arginine, L-citrulline delivers more NO to the penis then when either one is used alone.
L-arginine and L-citrulline are readily available at most health food or nutritional supplement stores. If you are considering using these either for their muscle pump or for their penis “pump”, you should start slowly. L-arginine may occasionally cause gastric upset or diarrhea or cramping. L-arginine and L-citrulline are relatively safe and usually do not affect any medications you may be taking. However, to be safe, check with your physician before starting them.
L-arginine and L-citrulline, as well as Viagra and Cialis and other “penis pills,” are not “site-specific”, i.e. they cause all vessels to dilate, including the vessels in your heart and brain so they benefit more than just your penis. However, if you are taking nitroglycerin or similar medications, L-arginine (as well as Viagra and Cialis) may cause “an unsafe drop” in blood pressure, especially when arising from a sitting or lying position. This could cause lightheadedness or fainting resulting in a fall or possible cardiovascular or cerebral injury. There is also the added risk of a heart attack if the high NO levels are sustained for too long. You should not take L-arginine or L-citrulline if you are taking nitroglycerin or other medications that contain nitroglycerin for high blood pressure..
The staff and physician of Renewal Medical Centers of North Texas are available to answer any questions you may have about this topic or any other questions about treatment for Erectile Dysfunction.