NAC (N-Acetyl Cysteine) vs Selenium (Selenomethionine)
Immune vs Mineral · evidence-backed comparison
- • NAC (N-Acetyl Cysteine) has the stronger evidence base (strong (multiple rcts / meta-analyses)).
- • NAC (N-Acetyl Cysteine) has the broader effect profile across the 9 effect categories.
- • Selenium (Selenomethionine) is cheaper per serving ($0.10 vs $0.22).
- • NAC (N-Acetyl Cysteine) has a slightly cleaner safety profile.
- • Selenium (Selenomethionine) has higher bioavailability (better absorption).
Side-by-side traits
| Trait | NAC (N-Acetyl Cysteine) | Selenium (Selenomethionine) |
|---|---|---|
Category | Immune | Mineral |
Active compound | N-acetyl L-cysteine | Selenomethionine |
Form available | Capsule, Powder | Capsule, Tablet |
Source | synthetic | synthetic |
Typical dose | 600–1800 mg daily | 100–200 mcg daily |
Dose range | 600–1800 mg | 100–200 mcg |
Loading protocol | — | — |
Best taken with | empty stomach or with food | with food |
Best time of day | any | any |
Bioavailability How efficiently the body absorbs and utilizes the compound. | Moderate (3/5) | Very High (5/5) |
Onset time | Acute and cumulative | Cumulative: 4–12 weeks |
Half-life | ~6 hours | ~252 days (long body store) |
Evidence level Quality and quantity of human research. | Strong (multiple RCTs / meta-analyses) | Moderate (some RCTs) |
Overall effect Subjective effect magnitude. | Moderate (3/5) | Low (2/5) |
Muscle / strength | Low (2/5) | Very Low (1/5) |
Physical energy | Low (2/5) | Low (2/5) |
Focus / cognition | Low (2/5) | Very Low (1/5) |
Mood / stress | Moderate (3/5) | Low (2/5) |
Sleep quality | Very Low (1/5) | Very Low (1/5) |
Immunity | High (4/5) | Moderate (3/5) |
Recovery Post-exercise recovery support. | Moderate (3/5) | Low (2/5) |
Longevity / healthspan | High (4/5) | Moderate (3/5) |
Safety rating 5 = exceptionally well-tolerated; 1 = significant risk profile. | High (4/5) | Moderate (3/5) |
Price per serving Approximate USD per typical daily dose. | $0.22 | $0.10 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About NAC (N-Acetyl Cysteine)
Glutathione precursor used clinically for liver protection (acetaminophen overdose). Strong evidence for OCD, COPD, and PCOS.
About Selenium (Selenomethionine)
Cofactor for glutathione peroxidase and thyroid hormone activation. Two Brazil nuts per day already meet requirements; toxicity above 400 mcg.
Vetted brands, third-party testing, ships worldwide.
Vetted brands, third-party testing, ships worldwide.
NAC (N-Acetyl Cysteine) safety
Common side effects:
- • Sulfur smell
- • GI upset
- • Headache
Avoid if:
- • Asthma (rare bronchospasm)
Drug interactions:
- • Nitroglycerin
- • Anticoagulants
- • Activated charcoal
Selenium (Selenomethionine) safety
Common side effects:
- • Selenosis (>400 mcg/day): hair loss, garlic breath, brittle nails
Avoid if:
- • Already eating Brazil nuts daily
Drug interactions:
- • Anticoagulants
Common uses
- • Liver protection
- • Lung health
- • OCD / mental health
- • PCOS
Stacks well with: Vitamin C, Selenium (Selenomethionine)
Common uses
- • Thyroid support
- • Hashimoto's
- • Antioxidant
Stacks well with: Iodine (Potassium Iodide)
Related comparisons
Medical disclaimer
SupplementDuel is for educational purposes only and is not medical advice. Consult a physician before starting, stopping, or combining supplements — especially if you are pregnant, breastfeeding, take prescription medication, or have a chronic condition.