Magnesium Glycinate vs Selenium (Selenomethionine)
Sleep vs Mineral · evidence-backed comparison
- • Magnesium Glycinate has the broader effect profile across the 9 effect categories.
- • Selenium (Selenomethionine) is cheaper per serving ($0.10 vs $0.25).
- • Magnesium Glycinate has a slightly cleaner safety profile.
Side-by-side traits
| Trait | Magnesium Glycinate | Selenium (Selenomethionine) |
|---|---|---|
Category | Sleep | Mineral |
Active compound | Magnesium chelated to glycine | Selenomethionine |
Form available | Capsule, Powder, Tablet | Capsule, Tablet |
Source | synthetic | synthetic |
Typical dose | 200–400 mg elemental Mg | 100–200 mcg daily |
Dose range | 200–400 mg | 100–200 mcg |
Loading protocol | — | — |
Best taken with | evening, with water | 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 | Acute: 1–3 hours | Cumulative: 4–12 weeks |
Half-life | ~28 hours (Mg) | ~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 | Moderate (3/5) | 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 | High (4/5) | Very Low (1/5) |
Immunity | Low (2/5) | 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. | Very High (5/5) | Moderate (3/5) |
Price per serving Approximate USD per typical daily dose. | $0.25 | $0.10 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Magnesium Glycinate
The best-tolerated, best-absorbed magnesium form for sleep and stress. Doesn't cause loose stools like citrate.
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 Glycinate safety
Common side effects:
- • Mild laxative effect (rare)
- • Drowsiness
Avoid if:
- • Severe kidney disease
Drug interactions:
- • Bisphosphonates
- • Antibiotics (timing)
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
- • Sleep quality
- • Anxiety
- • Muscle cramps
- • RLS
Stacks well with: Zinc, Vitamin D3, Melatonin
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.