NAC (N-Acetyl Cysteine) vs NMN (Nicotinamide Mononucleotide)

Mechanism

NAC is a precursor to L-cysteine, the rate-limiting substrate for glutathione (GSH) synthesis via glutamate-cysteine ligase. It directly replenishes intracellular GSH, the master endogenous antioxidant. NAC also modulates glutamatergic neurotransmission by stimulating the cystine-glutamate antiporter (system Xc-), influencing extrasynaptic glutamate levels. Additionally, it acts as a mucolytic by cleaving disulfide bonds in mucus glycoproteins.

Standard Dosing

600-1200mg daily

Timing

On empty stomach for best absorption, 30 min before meals. Split doses if >600mg.

Cycle Duration

Cycle 8 weeks on, 2 weeks off (to avoid potential downregulation of endogenous GSH production)

Side Effects

• Nausea
• GI upset
• Sulfurous odor/taste
• Rare: skin rash
• Potential zinc/copper chelation at very high doses

Contraindications

• Active gastric ulcers (may increase gastric acid)
• Asthma (rare bronchospasm with inhaled form)
• Concurrent chemotherapy (discuss with oncologist)

Best Stacking Partners

Mechanism

NMN is a direct biosynthetic precursor to NAD+ via the salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT). Elevated NAD+ activates sirtuins (SIRT1-7), PARP DNA repair enzymes, and CD38/CD157 signaling. SIRT1 activation deacetylates PGC-1alpha (mitochondrial biogenesis), FOXO transcription factors (stress resistance), and NF-kB (anti-inflammatory). NMN also enters cells via the Slc12a8 transporter, recently identified in the gut.

Standard Dosing

500-1000mg daily

Timing

Morning on empty stomach. Sublingual absorption bypasses first-pass metabolism.

Cycle Duration

ongoing

Side Effects

• Mild GI discomfort
• Flushing (rare, unlike niacin)
• Mild headache during initial use

Contraindications

• Active cancer (theoretical concern: NAD+ may fuel rapidly dividing cells)
• Pregnancy/lactation (insufficient data)
• Theoretical concern in active cancer (NAD+ fuels all rapidly dividing cells)

Best Stacking Partners