# item.guide
Side-by-Side Comparison Essential Vitamins & Minerals

Selenium (Elemental Se) vs. Vitamin D3 (Cholecalciferol)

Comparing 2 standards across 9 specifications. 9 key differences identified.

Comparing:
Selenium (Elemental Se)
Vitamin D3 (Cholecalciferol)
Selenium (Elemental Se) →

Selenium is an essential trace element incorporated as Selenocysteine (the 21st amino acid) into 25 human selenoproteins including Glutathione Peroxidases (GPx) and Iodothyronine Deiodinases (T4->T3 conversion). Adult RDA is 55 µg, with a Tolerable Upper Limit of 400 µg/day.

View full Selenium (Elemental Se) spec sheet →
Vitamin D3 (Cholecalciferol) →

Vitamin D3 is a secosteroid prohormone synthesized endogenously in skin via solar UVB irradiation of 7-dehydrocholesterol. Adult RDA is 600–800 IU (15–20µg), with a Tolerable Upper Limit of 4,000 IU (100µg)/day, regulating systemic calcium absorption and immune gene expression.

View full Vitamin D3 (Cholecalciferol) spec sheet →

Specification Comparison Table

9 Parameters
Parameter / Spec
Selenium (Elemental Se)
Vitamin D3 (Cholecalciferol)
Nutrient Type
Essential Trace Element Fat-Soluble Secosteroid Prohormone
Adult RDA / RDI
55 µg / day (60 µg pregnancy, 70 µg lactation) 600 – 800 IU / day (15 – 20 µg)
Tolerable Upper Limit (UL)
400 µg / day (Avoid selenosis / garlic breath, hair/nail brittleness) 4,000 IU / day (100 µg) (Endocrine Society: up to 10,000 IU safe)
Chemical Forms
Selenomethionine (Plant organic), Selenocysteine (Animal selenoprotein), Sodium Selenite / Selenate (Inorganic) Cholecalciferol (D3 - Animal/Lichen), Ergocalciferol (D2 - Fungi)
Primary Biological Function
Glutathione Peroxidase (GPx1-4) lipid hydroperoxide neutralization, Iodothyronine Deiodinases (Converts thyroid T4 into active T3), Thioredoxin Reductase (TXNRD) Calcitriol receptor (VDR) activation, intestinal calcium/phosphorus absorption, antimicrobial peptide synthesis
Deficiency Condition
Keshan Disease (Endemic juvenile cardiomyopathy), Kashin-Beck Disease (Deforming osteoarthropathy), Impaired thyroid metabolism Rickets (children), Osteomalacia (adults), Immune dysregulation
Top Whole Food Sources
Brazil Nuts (1 single nut provides ~70–90µg / 130–160% RDA), Eastern Oysters, Yellowfin Tuna, Halibut, Sardines, Beef Liver, Eggs Sunlight UVB, Atlantic Salmon, Sardines, Egg Yolk, Fortified Milk
Soil Selenium Geographical Variability
Plant selenium reflects regional soil content; volcanic soils (South America, Great Plains) are rich, while parts of China, Scandinavia, and New Zealand are depleted —
Target Serum 25(OH)D Level
— 30 – 50 ng / mL (75 – 125 nmol / L)

Other Alternatives to Compare

Compare Selenium (Elemental Se) vs. Calcium (Elemental Ca) → Compare Selenium (Elemental Se) vs. Iodine (Elemental I) → Compare Selenium (Elemental Se) vs. Iron (Heme & Non-Heme) → Compare Selenium (Elemental Se) vs. Magnesium (Elemental Mg) → Compare Selenium (Elemental Se) vs. Potassium (Elemental K) → Compare Selenium (Elemental Se) vs. Sodium (Elemental Na) → Compare Selenium (Elemental Se) vs. Vitamin A (Retinol & Beta-Carotene) → Compare Selenium (Elemental Se) vs. Vitamin B1 (Thiamine) → Compare Selenium (Elemental Se) vs. Vitamin B12 (Cobalamin) → Compare Selenium (Elemental Se) vs. Vitamin B2 (Riboflavin) → Compare Selenium (Elemental Se) vs. Vitamin B3 (Niacin / Nicotinic Acid & Nicotinamide) → Compare Selenium (Elemental Se) vs. Vitamin B5 (Pantothenic Acid) → Compare Selenium (Elemental Se) vs. Vitamin B6 (Pyridoxal 5'-Phosphate / PLP) → Compare Selenium (Elemental Se) vs. Vitamin B7 (Biotin / Vitamin H) → Compare Selenium (Elemental Se) vs. Vitamin B9 (Folate & Folic Acid) → Compare Selenium (Elemental Se) vs. Vitamin C (L-Ascorbic Acid) → Compare Selenium (Elemental Se) vs. Vitamin E (d-Alpha-Tocopherol) → Compare Selenium (Elemental Se) vs. Vitamin K1 (Phylloquinone) → Compare Selenium (Elemental Se) vs. Zinc (Elemental Zn) →