Vitamin D3
Vitamin D3 (Cholecalciferol)
The 'sunshine vitamin' essential for immune function, mood, bone health, and regulating over 1,000 genes in the body.
Vitamin D3 is a fat-soluble vitamin that functions as a hormone in the body. Deficiency is extremely common, especially in northern latitudes, and is linked to poor immune function, depression, muscle weakness, and bone loss. Optimal blood levels are 40-60 ng/mL.
Mechanisms of Action
Immune Regulation
Modulates both innate and adaptive immune responses
Gene Expression
Regulates over 1,000 genes throughout the body
Calcium Metabolism
Essential for calcium absorption and bone health
Recommended Dose
2000-5000 IU daily
Loading: If severely deficient (<20 ng/mL): 50,000 IU weekly for 8 weeks under medical supervision
Optimal Timing
- Morning with breakfast
Take with food
Best Form
D3 (cholecalciferol) softgel or liquid
Alternatives: D3 tablets, D3 drops
D3 is more effective than D2 (ergocalciferol). Oil-based softgels or liquid drops absorb best. Test blood levels after 2-3 months.
Duration
Minimum: 8 weeks
Optimal: 12 weeks
Cycling: Not required
Note: Take with a meal containing fat for best absorption. Morning is preferred as evening doses may interfere with sleep in some people.
Stronger Immunity
Reduced frequency and severity of infections
Improved Mood
Better mood and reduced seasonal depression symptoms
More Energy
Reduced fatigue, especially if previously deficient
Better Muscle Function
Improved strength and reduced muscle pain
Generally recommended; 1000-4000 IU is considered safe
Often need higher doses due to reduced skin synthesis
May need higher doses; melanin reduces vitamin D synthesis
Who Should NOT Take This
- Hypercalcemia
- Kidney disease (consult doctor)
- Sarcoidosis or other granulomatous diseases
Drug Interactions
May increase calcium levels
Steroids may reduce vitamin D absorption
Both metabolized by liver; monitor if using high doses
Possible Side Effects
Tip: Don't exceed 10,000 IU daily without monitoring
Tip: Take with food
Warnings
- Test blood levels before and during supplementation
- Target 40-60 ng/mL for optimal levels
- Toxicity is rare but possible with mega-doses
Martineau AR et al. • BMJ (2017)
“Vitamin D supplementation reduced the risk of acute respiratory tract infection, with stronger effects in those with profound deficiency.”
Key Findings:
- 12% reduction in respiratory infections overall
- 70% reduction in severely deficient individuals
- Daily/weekly dosing more effective than large boluses
Anglin RE et al. • British Journal of Psychiatry (2013)
“Low vitamin D levels are associated with depression, and supplementation may improve symptoms in deficient individuals.”
Key Findings:
- Low vitamin D associated with depression
- Supplementation benefits those who are deficient
- Effect strongest when correcting deficiency
Stockton KA et al. • Osteoporosis International (2011)
“Vitamin D supplementation improves muscle strength, particularly in individuals with baseline vitamin D deficiency.”
Key Findings:
- Improves muscle strength in deficient individuals
- Reduces fall risk in elderly
- Effects on strength in non-deficient unclear
Bouillon R et al. • Endocrine Reviews (2023)
“Vitamin D supplementation does not benefit bone or reduce fractures in vitamin D-replete adults, but correcting deficiency is essential.”
Key Findings:
- No benefit in vitamin D-replete individuals
- Correcting deficiency remains important
- Benefits seen primarily in those with severe deficiency
D'Ecclesiis O et al. • Nutrients (2024)
“Vitamin D may play a protective role in COVID-19, particularly in those with deficiency.”
Key Findings:
- Potential protective effect against infection
- Benefits linked to correcting deficiency
- Immune function support in deficient individuals
AI-discovered studies. Verify citations before citing.
Vitamin D supplementation and cardiovascular disease prevention: an updated meta-analysis of randomized controlled trials
Zhang Y et al. • European Heart Journal (2024)
This updated meta-analysis provides new evidence for vitamin D's cardiovascular benefits, particularly in deficient populations.
- Modest reduction in cardiovascular mortality with vitamin D supplementation
- Significant blood pressure reduction in hypertensive individuals
- Benefits most pronounced in individuals with baseline vitamin D deficiency
Preventive Vitamin D Supplementation and Risk for COVID-19 Infection: A Systematic Review and Meta-Analysis
DOID'Ecclesiis O et al. • Nutrients (2024)
Vitamin D may play a protective role in COVID-19, particularly in those with deficiency.
- Potential protective effect against infection
- Benefits linked to correcting deficiency
- Immune function support in deficient individuals
Health Effects of Vitamin D Supplementation: Lessons Learned From Randomized Controlled Trials and Mendelian Randomization Studies
Bouillon R et al. • Endocrine Reviews (2023)
Vitamin D supplementation does not benefit bone or reduce fractures in vitamin D-replete adults, but correcting deficiency is essential.
- No benefit in vitamin D-replete individuals
- Correcting deficiency remains important
- Benefits seen primarily in those with severe deficiency