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

Iron (Heme & Non-Heme) vs. Vitamin D3 (Cholecalciferol)

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

Comparing:
Iron (Heme & Non-Heme)
Vitamin D3 (Cholecalciferol)
Iron (Heme & Non-Heme) →

Iron is an essential redox trace element central to hemoglobin oxygen transport, myoglobin storage, and mitochondrial electron transport chain cytochromes. Adult RDA is 8mg (men/post-menopausal women) / 18mg (pre-menopausal women), with a Tolerable Upper Limit of 45mg/day.

View full Iron (Heme & Non-Heme) 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
Iron (Heme & Non-Heme)
Vitamin D3 (Cholecalciferol)
Nutrient Type
Essential Trace Mineral Fat-Soluble Secosteroid Prohormone
Adult RDA / RDI
8 mg (Men) / 18 mg (Women 19–50) / 27 mg (Pregnancy) 600 – 800 IU / day (15 – 20 µg)
Tolerable Upper Limit (UL)
45 mg / day (Hemochromatosis / Fenton reaction oxidative stress) 4,000 IU / day (100 µg) (Endocrine Society: up to 10,000 IU safe)
Chemical Forms
Heme Iron (Fe2+ Porphyrin - Animal), Non-Heme Iron (Fe3+ Ferric / Fe2+ Ferrous - Plants/Supplements) Cholecalciferol (D3 - Animal/Lichen), Ergocalciferol (D2 - Fungi)
Primary Biological Function
Hemoglobin O2 transport, Myoglobin O2 storage, Cytochrome c electron transport, Catalase Calcitriol receptor (VDR) activation, intestinal calcium/phosphorus absorption, antimicrobial peptide synthesis
Deficiency Condition
Microcytic Hypochromic Anemia, Severe fatigue, Restless legs syndrome, Pica Rickets (children), Osteomalacia (adults), Immune dysregulation
Top Whole Food Sources
Beef Liver, Oysters, Duck Breast, Beef Ribeye, Lentils, Spinach, Dark Chocolate Sunlight UVB, Atlantic Salmon, Sardines, Egg Yolk, Fortified Milk
Bioavailability Difference
Heme: 15–35% absorption (uninhibited); Non-Heme: 2–20% (inhibited by phytates/calcium, boosted by Vitamin C) —
Target Serum 25(OH)D Level
— 30 – 50 ng / mL (75 – 125 nmol / L)

Other Alternatives to Compare

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