Comparison
Vitamin D3 vs Selenium
Vitamin D3
Hormone-like vitamin synthesized in skin from UVB. Profoundly involved in brain function, mood, and inflammation.
Selenium
Essential trace mineral; cofactor for glutathione peroxidase and thyroid hormone activation. Brazil nuts are the densest food source.
| Field | Vitamin D3 | Selenium |
|---|---|---|
| Category | vitamin | vitamin |
| Dose range | 0.025–0.125mg | 0.05–0.2mg |
| Half-life | 360h | — |
| Onset | — | — |
| Evidence | EVIDENCEA | EVIDENCEA |
| Safety | ●●●●● | ●●●●○ |
| Legal (US) | USOTC | USOTC |
| PubMed refs | 9200 | 4400 |
The comparison in plain English
Auto-generated from dataVitamin D3 and Selenium are both in the vitamin category respectively. Vitamin D3 Hormone-like vitamin synthesized in skin from UVB. Selenium Essential trace mineral; cofactor for glutathione peroxidase and thyroid hormone activation.
Bottom line
Vitamin D3 (evidence A, safety 5/5) matches the evidence base of Selenium (evidence A, safety 4/5). Vitamin D3 has the slightly cleaner safety profile. For users new to either, the higher-evidence option is the safer first try.
Choose Vitamin D3 if
Vitamin D3 is the better fit when your goal aligns with its mechanism (Vitamin D3 (cholecalciferol) is converted to 25-hydroxyvitamin D in the liver and then to the active hormone 1,25-dihydroxyvitamin D (calcitriol) in the kidneys) and the dose range (0.025–0.125mg) suits your protocol. Half-life is 360h.
Choose Selenium if
Selenium is the better fit when your goal aligns with its mechanism (Selenium is incorporated into selenocysteine residues in roughly 25 selenoproteins, including the glutathione peroxidases (the primary cellular antioxidant defence) and the deiodinases that convert T4 to active T3 thyroid hormone) and the dose range (0.05–0.2mg) suits your protocol. Half-life is —h.