Vitamin D3
A prohormone essential for calcium metabolism, immune function, and gene expression. Deficiency affects ~1 billion people worldwide.
Evidence by Outcome
Bone Health
6% fracture risk reduction (JAMA 2019)
Cancer Mortality
16% reduction in cancer death (RR=0.84, 95% CI 0.74–0.95). D3 only; D2 shows no effect. BMJ 2019 meta-analysis.
Immune Function
12% reduction in respiratory infections (BMJ 2017)
All-cause Mortality
No significant reduction in all-cause mortality (RR=0.98, 95% CI 0.95–1.02). Vitamin D3 alone insufficient.
Autoimmune Disease
22% reduction (VITAL trial — 2000 IU/day over 5 years)
Dosing Guide
1000-2000 IU/day
With largest meal (fat-soluble)
D3 preferred over D2 (25% more effective). Test 25(OH)D levels. Obese individuals may need 2x dose.
Safety Profile
Possible Side Effects
- • Hypercalcemia at very high doses (>10,000 IU/day chronic)
Contraindications
- ⚠ Sarcoidosis
- ⚠ Severe kidney disease
- ⚠ Hypercalcemia
Known Interactions
Magnesium is required for Vitamin D activation. Low magnesium impairs D3 metabolism. Take together.
Source: J Am Osteopath Assoc, 2018
D3 increases calcium absorption; K2 directs calcium to bones instead of arteries. Always pair.
Source: Calcified Tissue International, 2017
Both fat-soluble — take together with a fatty meal for optimal absorption.
Source: General pharmacokinetic principle
Both fat-soluble, both support immune function. Take together with a fatty meal.
Source: Practical co-administration
Omega-3 may enhance vitamin D receptor expression. Both support immune function. Take together with fat.
Source: Nutrients, 2020
No known interaction. NMN for cellular energy, D3 for immune and bone. Can be taken together.
Source: No interaction data