L-Theanine vs Selenium (Selenomethionine)
Nootropic vs Mineral · evidence-backed comparison
- • L-Theanine has the broader effect profile across the 9 effect categories.
- • Selenium (Selenomethionine) is cheaper per serving ($0.10 vs $0.12).
- • L-Theanine has a slightly cleaner safety profile.
Side-by-side traits
| Trait | L-Theanine | Selenium (Selenomethionine) |
|---|---|---|
Category | Nootropic | Mineral |
Active compound | L-theanine | Selenomethionine |
Form available | Capsule, Powder | Capsule, Tablet |
Source | plant | synthetic |
Typical dose | 100–400 mg | 100–200 mcg daily |
Dose range | 100–400 mg | 100–200 mcg |
Loading protocol | — | — |
Best taken with | caffeine (1:2 ratio) | with food |
Best time of day | any | any |
Bioavailability How efficiently the body absorbs and utilizes the compound. | Very High (5/5) | Very High (5/5) |
Onset time | Acute: 30–60 min | Cumulative: 4–12 weeks |
Half-life | ~3 hours | ~252 days (long body store) |
Evidence level Quality and quantity of human research. | Moderate (some RCTs) | Moderate (some RCTs) |
Overall effect Subjective effect magnitude. | Moderate (3/5) | Low (2/5) |
Muscle / strength | Very Low (1/5) | Very Low (1/5) |
Physical energy | Low (2/5) | Low (2/5) |
Focus / cognition | High (4/5) | Very Low (1/5) |
Mood / stress | High (4/5) | Low (2/5) |
Sleep quality | Moderate (3/5) | Very Low (1/5) |
Immunity | Low (2/5) | Moderate (3/5) |
Recovery Post-exercise recovery support. | Very Low (1/5) | Low (2/5) |
Longevity / healthspan | Low (2/5) | Moderate (3/5) |
Safety rating 5 = exceptionally well-tolerated; 1 = significant risk profile. | Very High (5/5) | Moderate (3/5) |
Price per serving Approximate USD per typical daily dose. | $0.12 | $0.10 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About L-Theanine
Green tea amino that produces calm focus by raising alpha brain waves. Pairs perfectly with caffeine to take the edge off without sedation.
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.
L-Theanine safety
Common side effects:
- • Generally none
Avoid if:
- • Low blood pressure
Drug interactions:
- • Blood pressure meds
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
- • Calm focus
- • Anxiety reduction
- • Better sleep onset
Stacks well with: Caffeine
Common uses
- • Thyroid support
- • Hashimoto's
- • Antioxidant
Stacks well with: Iodine (Potassium Iodide)
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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.