Magnesium L-Threonate vs Selenium (Selenomethionine)
Sleep vs Mineral · evidence-backed comparison
- • Selenium (Selenomethionine) has the stronger evidence base (moderate (some rcts)).
- • Magnesium L-Threonate has the broader effect profile across the 9 effect categories.
- • Selenium (Selenomethionine) is cheaper per serving ($0.10 vs $1.10).
- • Magnesium L-Threonate has a slightly cleaner safety profile.
Side-by-side traits
| Trait | Magnesium L-Threonate | Selenium (Selenomethionine) |
|---|---|---|
Category | Sleep | Mineral |
Active compound | Magnesium L-threonate | Selenomethionine |
Form available | Capsule, Powder | Capsule, Tablet |
Source | synthetic | synthetic |
Typical dose | 1.5–2 g (≈144 mg elemental Mg) | 100–200 mcg daily |
Dose range | 1500–2000 mg | 100–200 mcg |
Loading protocol | — | — |
Best taken with | evening | with food |
Best time of day | evening | any |
Bioavailability How efficiently the body absorbs and utilizes the compound. | Very High (5/5) | Very High (5/5) |
Onset time | Cumulative: 4–12 weeks | Cumulative: 4–12 weeks |
Half-life | — | ~252 days (long body store) |
Evidence level Quality and quantity of human research. | Limited (small studies) | 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 | Very Low (1/5) | Low (2/5) |
Focus / cognition | High (4/5) | Very Low (1/5) |
Mood / stress | Moderate (3/5) | Low (2/5) |
Sleep quality | High (4/5) | Very Low (1/5) |
Immunity | Very Low (1/5) | Moderate (3/5) |
Recovery Post-exercise recovery support. | Very Low (1/5) | Low (2/5) |
Longevity / healthspan | Moderate (3/5) | 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. | $1.10 | $0.10 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Magnesium L-Threonate
Only magnesium form proven to cross the blood-brain barrier in animals. Marketed for cognitive aging and sleep, but premium-priced.
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.
Magnesium L-Threonate safety
Common side effects:
- • Drowsiness
- • Headache (rare)
Avoid if:
- • Severe kidney disease
Drug interactions:
- • Bisphosphonates
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
- • Cognitive aging
- • Deep sleep
- • Memory
Stacks well with: Zinc, Vitamin D3
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.