Vitamin D
Cholecalciferol (D3) / Ergocalciferol (D2)
Vitamin D is a fat-soluble vitamin that functions more like a hormone, affecting nearly every tissue in the body. It's synthesized in skin from sunlight but many people are deficient due to indoor lifestyles, sunscreen use, and geographic location. It's essential for calcium absorption, bone health, immune function, and mood.
How It Works
Vitamin D undergoes activation and acts through nuclear receptors:
- Activation: D3 (from sun/supplements) → 25(OH)D (liver) → 1,25(OH)₂D (calcitriol, active form, in kidneys and other tissues).
- VDR (Vitamin D Receptor): Calcitriol binds to VDR in the nucleus, regulating over 200 genes involved in calcium metabolism, cell growth, immune function, and more.
- Calcium Absorption: Upregulates calcium-binding proteins in intestines, increasing calcium absorption from about 10-15% to 30-40%.
- Bone Health: Essential for bone mineralization and remodeling.
- Immune Modulation: Enhances innate immunity (antimicrobial peptides like cathelicidin) while modulating adaptive immunity (may reduce autoimmune risk).
Key Benefits
Vitamin D is essential for:
- Supporting bone density and fracture prevention by enabling calcium absorption and bone mineralization.
- Maintaining immune function, with deficiency linked to higher risk of respiratory infections.
- Helping regulate mood and cognitive health, with low levels associated with depression and cognitive decline.
- Supporting muscle function and overall physical performance, especially in older adults.
How Vitamin D is Used
- Bone health & osteoporosis: Combined with calcium and sometimes vitamin K for maintaining bone density and preventing fractures.
- Immune support: Used to correct deficiency in people at higher latitudes or with low sun exposure.
- Metabolic and autoimmune conditions: Observational research suggests roles in autoimmune disease risk and metabolic health.
Always base dosing on blood testing where possible and follow established guidelines (keeping 25(OH)D in the 40–60 ng/mL range is often recommended).
Natural Food Sources
| Food | Amount per Serving |
|---|---|
| Salmon (wild) | 570-800 IU per 3 oz |
| Sardines | 164 IU per 3 oz |
| Sardines | 115-130 IU per cup |
| Fortified milk | 40 IU per large egg |
| Egg yolk | 100 IU per cup |
| Fortified orange juice | 400+ IU per 3 oz |
Safety Information
Contraindications
- Hypercalcemia - vitamin D will further raise calcium
- Sarcoidosis and granulomatous diseases - risk of hypercalcemia
- Sarcoidosis and granulomatous diseases - risk of hypercalcemia
Potential Side Effects
- Very safe at recommended doses (rare)
- Hypercalcemia (very high doses: weakness, nausea, kidney stones) (rare)
- Hypercalcemia (very high doses: weakness, nausea, kidney stones) (rare)
Scientific Research
Vitamin D and Calcium Supplementation Reduces Cancer Risk
JAMA Network Open
This large analysis of multiple studies found that taking vitamin D supplements, especially along with calcium, may help reduce the overall risk of developing cancer. The protective effect was strongest when people took at least 1000 IU of vitamin D daily. While this is promising, more research is needed to understand which specific cancers might be prevented and who benefits most.
Vitamin D Supplementation and COVID-19 Outcomes
Scientific Reports
This analysis of multiple studies found that people with low vitamin D levels were more likely to have severe COVID-19 illness and higher risk of death. While this doesn’t prove that vitamin D prevents COVID-19, it suggests that maintaining adequate vitamin D levels (30-50 ng/mL in blood) may support immune function during respiratory infections. Taking vitamin D supplements may be particularly important for those who are deficient.
Vitamin D and Depression: A Systematic Review and Meta-Analysis
Critical Reviews in Food Science and Nutrition
This review of 41 clinical trials found that vitamin D supplements can help reduce symptoms of depression, especially in people who have clinical depression or who are deficient in vitamin D. Taking at least 2000 IU daily appears to be most effective. While not a replacement for standard depression treatment, vitamin D may be a helpful addition to mental health care.
Disclaimer: The information provided is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare provider before starting any supplement regimen.