Vitamin D
Vitamin D is a hormone-like vitamin that influences hundreds of genes. Huberman discusses its roles in mood, immunity, testosterone, and overall health—and why deficiency is epidemic in modern life.
What Vitamin D Does
| System | Effect |
|---|---|
| Immune | Modulates immune response |
| Mood | Involved in serotonin synthesis |
| Bone | Calcium absorption and bone density |
| Hormones | Supports testosterone production |
| Brain | Neuroprotective effects |
| Muscle | Function and strength |
Vitamin D receptors exist in virtually every tissue—it’s truly systemic.
Why Deficiency Is Common
Modern life limits vitamin D:
- Indoor work and lifestyle
- Sunscreen blocks synthesis
- Living at high latitudes
- Darker skin requires more sun exposure
- Aging reduces synthesis capacity
Estimates suggest 40-50% of the population is deficient.
Testing and Optimal Levels
| Level (ng/mL) | Status |
|---|---|
| <20 | Deficient |
| 20-30 | Insufficient |
| 30-50 | Adequate |
| 40-60 | Optimal (Huberman’s suggested range) |
| >100 | Potentially toxic |
Get tested—you can’t know your status without measuring.
Sources
Sunlight
The body makes vitamin D from cholesterol when skin is exposed to UVB:
- 10-30 minutes midday sun (depending on skin tone, latitude)
- More melanin = more time needed
- Winter at high latitudes = minimal synthesis
- Sunscreen blocks production
Food
Limited dietary sources:
- Fatty fish (salmon, mackerel)
- Egg yolks
- Fortified foods
- Cod liver oil
Diet alone rarely provides adequate levels for most people.
Supplementation
Often necessary, especially in winter:
| Form | Notes |
|---|---|
| D3 (cholecalciferol) | Preferred, more effective |
| D2 (ergocalciferol) | Less effective |
Common doses: 1,000-5,000 IU daily (higher may be needed if deficient)
Vitamin D and K2
These work together:
The Synergy
- Vitamin D increases calcium absorption
- Vitamin K2 directs calcium to bones (not arteries)
- Together, they support bone health safely
- Many recommend taking them together
K2 forms: MK-4 and MK-7 (MK-7 has longer half-life)
Vitamin D and Mood
Connections to mental health:
- Required for serotonin synthesis
- Deficiency associated with depression
- Seasonal affective disorder linked to low D
- May enhance antidepressant response
Not a standalone depression treatment, but deficiency should be corrected.
Vitamin D and Immunity
Effects on immune function:
- Enhances innate immunity
- Modulates adaptive immunity
- May reduce infection risk
- Anti-inflammatory effects
Adequate vitamin D supports immune balance.
Vitamin D and Testosterone
Supports hormone production:
- Required for testosterone synthesis
- Deficient men have lower T
- Supplementation may increase T in deficient individuals
- Not a substitute for other interventions if sufficient
Practical Protocol
- Test your levels - Know your starting point
- Get sunlight when possible - 10-30 min midday without sunscreen
- Supplement if needed - D3, typically 1,000-5,000 IU
- Consider K2 - Especially if supplementing D long-term
- Retest - Verify levels after 2-3 months
Safety Considerations
Vitamin D is fat-soluble—excess can accumulate:
- Upper limit typically 4,000 IU/day (can be exceeded with testing)
- Toxicity rare but possible with very high doses
- Monitor levels if taking >5,000 IU daily
- More isn’t always better
Related Pages
“Vitamin D deficiency is one of the most common and most easily correctable issues. Get tested, and if you’re low, address it—it affects nearly every system in your body.” — Andrew Huberman