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Unlocking the Power of Nitric Oxide: The Science Behind Erections

Updated: Sep 14, 2023

How Does an Erection Occur?

Understanding the Nitric Oxide pathway is the key to understanding how an erection occurs. If you understand it, you will also realize what PDE5 inhibitors, like Viagra and Cialis, do and why they may stop working.

Diagram of the Nitric Oxide Pathway
Diagram of the Nitric Oxide Pathway

This image has been made available via the Creative Commons Attribution 4.0 License, and it originally appeared in the article Development and therapeutic applications of nitric oxide releasing materials to treat erectile dysfunction

The Nitric Oxide Pathway

The process by which an erection occurs is complex and involves both the nervous system and the vascular system. The Nitric Oxide (NO) pathway is critical in this process. Here is a very high-level description.

Sexual Stimulation: The process begins with sexual stimulation, which can be physical (such as touch) or mental (such as erotic thoughts). This stimulation generates nerve impulses in the brain and sends them to the nerves responsible for erectile function.

Nitric Oxide Production: The nerve signals trigger the production of Nitric Oxide (NO) in the endothelial cells that line the penile arteries and the erectile bodies within the penis. Nitric Oxide is a potent vasodilator that causes blood vessels to widen.

Cyclic Guanosine Monophosphate (cGMP) Production: The Nitric Oxide (NO) then stimulates the production of a substance called cyclic Guanosine Monophosphate (cGMP) in the muscle cells of the corpora cavernosa (two cylindrical tissues running the length of the penis). cGMP causes the smooth muscle in these tissues to relax.

Blood Inflow and Erection: When the smooth muscle relaxes, the blood vessels widen, and blood flow into the penis increases. As a result, the erectile tissues engorge with blood, and an erection occurs.

Maintenance and Termination of Erection: The erection is maintained as long as the cGMP is present in sufficient amounts. The enzyme Phosphodiesterase Type 5 (PDE5) works to degrade cGMP. When sexual stimulation ends, NO production decreases, the level of cGMP falls due to PDE5 action, the smooth muscles contract again, blood flow decreases, and the erection subsides.

So What are the Practical Implications?

The importance of the NO pathway in maintaining an erection is why PDE5 inhibitors like sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) are used to treat erectile dysfunction. These medications work by blocking the action of PDE5, which means cGMP is not broken down, and the smooth muscle relaxation is enhanced, promoting more blood flow to the penis and making it easier to achieve an erection.

It's also important to understand that PDE5 inhibitors do not work without adequate Nitric Oxide (NO) to induce an erection. As we age, our ability to produce Nitric Oxide decreases. Many men start on PDE5 inhibitors. The pills work for a while, then stop working. One reason they may stop working is Nitric Oxide is no longer produced sufficiently to get the erection started.

How Do You Increase the Nitric Oxide (NO) Levels in Your Body?

To raise Nirtric Oxide levels in the body to the following.

  • Eat large amounts of vegetables high in nitrates. Spinach and Beets are two examples, but there are many. Generally, green leafy vegetables are good sources of nitrates, but do a Google search to get a list.

  • Chew those vegetables well and allow the saliva to break them down and release the Nitrates.

  • Stop using alcohol-based mouthwash! It kills the good bacteria in your mouth, which you need to break down the nitrate-rich vegetables. You may have to rebuild your oral microbiome if you use alcohol-based mouthwash. See the article in the references.


There are supplements you can take to help build your Nitric Oxide levels. I take a supplement from Berkley Life (link below). L-Arginine and L-Citrulline are common supplements that boost the Nitric Oxide pathway. Unfortunately, their byproducts can build up in toxic amounts with regular use. L-Arginine and L-Citrulline should only be considered for short-term or occasional use!



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