Arginine
The nitric oxide maker. Arginine is the only substrate for making NO - the molecule that relaxes blood vessels, supports immune function, and helps with exercise performance. It's also part of the urea cycle and creatine synthesis.
What Arginine Does
Nitric Oxide Synthesis
The ONLY substrate for NOS enzymes. Arginine → NO + citrulline. Requires BH4.
Blood Vessel Relaxation
NO dilates blood vessels, improving blood flow, reducing blood pressure.
Urea Cycle
Arginine is cleaved to urea + ornithine. Essential for ammonia detoxification.
Creatine Production
Arginine + glycine → guanidinoacetate → creatine (via SAMe).
Growth Hormone Release
Stimulates pituitary GH secretion. Used for this purpose in some studies.
Wound Healing
Supports collagen synthesis and immune function for tissue repair.
Arginine → Nitric Oxide
Nitric oxide (NO) is a signaling molecule that relaxes smooth muscle in blood vessel walls. This improves blood flow to the heart, muscles, brain, and yes, reproductive organs. Viagra works by enhancing NO signaling.
The reaction requires the cofactor BH4 (tetrahydrobiopterin). Without adequate BH4, NOS becomes "uncoupled" and produces superoxide instead of NO - actually causing oxidative damage rather than relaxation.
Benefits of Nitric Oxide
- • Lower blood pressure
- • Better exercise performance
- • Improved erectile function
- • Reduced angina
- • Immune cell killing ability
- • Neurotransmission
Citrulline vs Arginine Supplementation
L-Arginine
- +Direct precursor to NO
- −Poorly absorbed (intestinal arginase breaks it down)
- −First-pass liver metabolism
- −May cause GI upset at higher doses
- →Typical dose: 3-6g daily
L-Citrulline (Better Choice)
- +Bypasses intestinal arginase
- +Converted to arginine in kidneys
- +Raises plasma arginine more effectively
- +Better tolerated, less GI issues
- →Typical dose: 3-6g daily (or citrulline malate 6-8g)
The Arginine-Lysine Balance
Arginine and lysine compete for the same intestinal transporter. High arginine intake can reduce lysine absorption and vice versa.
This is relevant for herpes viruses (HSV-1, HSV-2), which require arginine to replicate. High arginine / low lysine may trigger outbreaks, while high lysine / low arginine may help prevent them.
If You Have Herpes
- •Be cautious with arginine supplements
- •Consider lysine supplementation (1-3g daily)
- •Avoid high-arginine foods during outbreaks
- •Nuts, chocolate, seeds are high in arginine
Dietary Sources
Highest Sources
Turkey, pork loin, chicken, pumpkin seeds, soybeans, peanuts.
Good Sources
Beef, fish, eggs, dairy, lentils, chickpeas, almonds.
Note
Most protein foods provide arginine. Deficiency is rare in people eating adequate protein.
