Vitamin D: The Sunshine Vitamin and Modern Deficiency Crisis

Vitamin D deficiency affects an estimated 1 billion people worldwide. Here's what you need to know.

## Beyond Bone Health

Vitamin D receptors exist in nearly every cell, influencing:

**Immune Function**: Modulates both innate and adaptive immunity
**Mental Health**: Linked to serotonin production and mood regulation
**Cardiovascular Health**: Affects blood pressure and inflammation
**Cancer Prevention**: May reduce risk of certain cancers

## Optimal Levels: Controversial Territory

**Conventional Medicine**: 20 ng/mL sufficient
**Functional Medicine**: 40-60 ng/mL optimal
**Endocrine Society**: >30 ng/mL for bone health

## Sources of Vitamin D

### Sunlight Synthesis
- 10-30 minutes midday exposure
- Without sunscreen initially
- Larger skin surface area = more production
- Difficult in winter at latitudes >37°

### Food Sources (limited)
- Fatty fish: 400-1000 IU per serving
- Egg yolks: 40 IU per egg
- Mushrooms (UV-exposed): 400+ IU
- Fortified foods: 100-400 IU per serving

### Supplementation
**D3 (cholecalciferol)** preferred over D2
- Typical dose: 1000-4000 IU daily
- Take with fat-containing meal
- Consider K2 supplementation alongside

## Who's at Risk?

- Dark skin pigmentation
- Older adults (reduced synthesis)
- Limited sun exposure
- Obesity (sequestration in fat tissue)
- Malabsorption conditions

## Testing Recommendations

Get 25-hydroxyvitamin D tested:
- Annually for at-risk populations
- Every 2-3 years for others
- 3 months after starting supplementation

## Safety Considerations

Vitamin D toxicity is rare but possible at very high doses (>10,000 IU daily long-term). Symptoms include hypercalcemia.