Vitamins

Vitamin D3

Evidence: strong_human

Mechanism of Action

Vitamin D3 (cholecalciferol) is hydroxylated in the liver to 25(OH)D (calcidiol), then in the kidneys to 1,25(OH)2D (calcitriol), the active hormone. Calcitriol binds the nuclear vitamin D receptor (VDR), forming a heterodimer with RXR that regulates >1000 genes. Key actions: upregulation of intestinal calcium/phosphorus absorption (TRPV6, calbindin), modulation of innate immunity (cathelicidin LL-37 antimicrobial peptide production), suppression of adaptive immune overactivation (Th1/Th17 to Treg shift), regulation of PTH and osteocalcin for bone mineralization, and modulation of insulin secretion from beta cells.

Dosing Protocol

Standard: 5000 IU daily (125 mcg)

Loading: 10,000 IU/day for 8-12 weeks to correct deficiency (<30 ng/mL), or 50,000 IU weekly under supervision

Maintenance: 2000-5000 IU/day (dose to maintain 25(OH)D at 50-80 ng/mL)

Administration: oralsublingual

Timing: With largest fat-containing meal of the day (fat-soluble). Morning preferred.

Duration: ongoing (lifelong for most people in northern latitudes)

Notes

ALWAYS co-supplement with Vitamin K2 (MK-7) to direct calcium to bones/teeth rather than soft tissues/arteries. Magnesium is required for D3 metabolism (4 of 8 enzymatic steps require Mg). Optimal blood level: 50-80 ng/mL (not just >30). Obese individuals require 2-3x higher doses due to sequestration in adipose tissue. Sun exposure produces D3 with a natural feedback mechanism that prevents toxicity — supplementation does not have this safeguard. Testing is mandatory before high-dose supplementation.

Stacking

  • Vitamin K2 (MK-7)
  • Magnesium
  • Zinc
  • Boron

Interactions

  • Thiazide diuretics [MEDIUM] — Both increase calcium retention; risk of hypercalcemia
  • Statins [LOW] — D3 uses the same CYP pathway as statins; generally synergistic for cardiovascular benefit
  • Corticosteroids [MEDIUM] — Chronic corticosteroids impair vitamin D metabolism and calcium absorption
  • Orlistat/cholestyramine [MEDIUM] — Fat malabsorption drugs reduce D3 absorption

Contraindications

  • Hypercalcemia
  • Granulomatous diseases (sarcoidosis, some lymphomas — unregulated 1-alpha hydroxylase conversion)
  • Primary hyperparathyroidism (without monitoring)
  • Williams syndrome

Side Effects

  • Hypercalcemia at excessive doses (>10,000 IU/day long-term without monitoring)
  • Nausea/vomiting (toxicity)
  • Kidney stones (with excessive calcium)
  • Metallic taste (toxicity sign)

Key Papers

  • 10.1056/NEJMoa1809944
  • 10.1136/bmj.i1903
  • 10.1210/jc.2011-0385

Source Quality

D3 (cholecalciferol) is superior to D2 (ergocalciferol) for raising and maintaining blood levels. Lanolin-derived is standard; lichen-derived available for vegans. Oil-based softgels preferred over tablets. Brands: Thorne D-5000, NatureWise, Bio-Tech Pharmacal (high-dose Rx). Test 25(OH)D blood levels quarterly until stable.

Disclaimer: This information is for educational purposes only and is not medical advice. BioAccelera Labs does not diagnose, treat, or prescribe. Consult a licensed healthcare provider before using any compound.

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