Nitric Oxide
The molecule that opens blood vessels. Nitric oxide (NO) is a gas that signals blood vessels to relax and dilate, improving blood flow everywhere - heart, brain, muscles, and more. Its discovery won the 1998 Nobel Prize in Medicine.
What Nitric Oxide Does
Vasodilation
Relaxes smooth muscle in blood vessel walls, widening them and improving blood flow.
Blood Pressure
Wider blood vessels = lower resistance = lower blood pressure. Especially systolic.
Exercise Performance
Improves oxygen delivery to muscles. Enhances endurance and reduces oxygen cost of exercise.
Platelet Function
Prevents platelets from sticking together and to vessel walls. Reduces clot risk.
Immune Defense
Macrophages use NO to kill pathogens. Part of innate immune response.
Erectile Function
NO dilates blood vessels in erectile tissue. Viagra works by prolonging NO signaling.
Two Ways to Make NO
1. NOS Pathway (Arginine)
- Arginine → NO via NOS enzymes
- Requires oxygen, BH4 cofactor
- eNOS (endothelial), nNOS (neuronal), iNOS (immune)
- Declines with age and disease
- Inhibited by ADMA (asymmetric dimethylarginine)
2. Nitrate Pathway (Diet)
- Dietary nitrate → nitrite → NO
- Converted by oral bacteria
- Works better in low-oxygen conditions
- Doesn't require NOS or BH4
- Backup system, especially as we age
How to Boost Nitric Oxide
Nitrate-Rich Foods
Beets, arugula, spinach, celery, lettuce. Beet juice is popular for athletes.
Citrulline
Converts to arginine. Better absorbed than arginine itself. Watermelon is a source.
Exercise
Blood flow shear stress activates eNOS. Regular exercise increases baseline NO production.
Sunlight
UV light releases NO from skin stores. May explain cardiovascular benefits of sun exposure.
Nose Breathing
Sinuses produce NO. Nose breathing delivers NO to lungs, improving oxygen uptake.
Don't Use Mouthwash
Kills oral bacteria needed to convert nitrate to nitrite. Linked to higher blood pressure.
What Depletes Nitric Oxide
Aging
NOS activity declines with age. Endothelial dysfunction increases. Nitrate pathway becomes more important.
Oxidative Stress
Superoxide reacts with NO, destroying it and creating peroxynitrite (toxic).
Antiseptic Mouthwash
Kills bacteria that convert dietary nitrate to nitrite. Use sparingly or not at all.