Biotin (B7) vs Selenium (Selenomethionine)
Vitamin vs Mineral · evidence-backed comparison
- • Selenium (Selenomethionine) has the stronger evidence base (moderate (some rcts)).
- • Selenium (Selenomethionine) has the broader effect profile across the 9 effect categories.
- • Biotin (B7) is cheaper per serving ($0.08 vs $0.10).
- • Biotin (B7) has a slightly cleaner safety profile.
Side-by-side traits
| Trait | Biotin (B7) | Selenium (Selenomethionine) |
|---|---|---|
Category | Vitamin | Mineral |
Active compound | D-biotin | Selenomethionine |
Form available | Capsule, Tablet, Gummy | Capsule, Tablet |
Source | microbial | synthetic |
Typical dose | 1000–10000 mcg daily | 100–200 mcg daily |
Dose range | 1000–10000 mcg | 100–200 mcg |
Loading protocol | — | — |
Best taken with | with food | 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 | Cumulative: 8–24 weeks | Cumulative: 4–12 weeks |
Half-life | ~26 hours | ~252 days (long body store) |
Evidence level Quality and quantity of human research. | Limited (small studies) | Moderate (some RCTs) |
Overall effect Subjective effect magnitude. | Low (2/5) | Low (2/5) |
Muscle / strength | Very Low (1/5) | Very Low (1/5) |
Physical energy | Very Low (1/5) | Low (2/5) |
Focus / cognition | Very Low (1/5) | Very Low (1/5) |
Mood / stress | Very Low (1/5) | Low (2/5) |
Sleep quality | Very Low (1/5) | 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 | Very Low (1/5) | 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. | $0.08 | $0.10 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Biotin (B7)
Popularly marketed for hair, skin, and nails — but evidence only supports use if frankly deficient. Stop 3 days before any thyroid test.
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.
Biotin (B7) safety
Common side effects:
- • Generally none
- • Interferes with thyroid blood tests
Avoid if:
- • Thyroid testing scheduled
Drug interactions:
- • Antiseizure meds
- • Lab assays
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
- • Hair / nails / skin
- • Biotin deficiency
- • Brittle nails
Stacks well with: Collagen Peptides
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.