Vitamin D3
Vitamin D3 (cholecalciferol) is a fat-soluble secosteroid produced in the skin when exposed to UVB radiation from sunlight. It can also be obtained through fatty fish, fortified foods, and supplements. Deficiency is remarkably common worldwide, particularly in higher latitudes, and the vitamin plays well-documented roles in calcium metabolism, immune regulation, and neurological function.
Expert Evidence
45 references from 4 experts
“Personally, I take 1,000 international units of vitamin D as part of MicroVitamin. That level helps me make sure I'm locking in the benefits of vitamin D without getting anywhere near the high doses that might lead to problems.”
Vitamin D Telomeres and Aging
9:4822 references in 16 episodes from 2022–2025
Brad Stanfield consistently supplements with vitamin D3 at 1,000-2,000 IU daily (via his MicroVitamin product) to prevent deficiency, while strongly cautioning against high doses (4,000+ IU), which he notes can reduce bone density and cause toxicity. He acknowledges vitamin D does not reduce cancer or cardiovascular disease risk but values it for calcium absorption, bone health, and potential autoimmune and telomere benefits.
Consumption
He takes 1,000-2,000 IU of vitamin D3 daily as part of his MicroVitamin multivitamin, often paired with vitamin K2; he previously took up to 4,000 IU daily for several years but has since reduced his dose.
Benefits
Vitamin D3 aids calcium absorption and works with K2 to direct calcium to bones and teeth; a large trial showed a 22% reduction in autoimmune disease risk, and supplementation may slow telomere loss.
Best Practices
He recommends 1,000 IU daily (especially for sunscreen users) and would not exceed 2,000-4,000 IU, consistent with Endocrine Society guidelines.
Cautions
High doses (4,000-10,000 IU) decreased wrist bone density by 2.4-3.5% and increased fall risk; large trials showed no benefit for cancer or cardiovascular disease; toxicity causes hypercalcemia, nausea, kidney stones, and muscle weakness.
“The sweet spot for vitamin D is between 40 to 60 nanograms per milliliter for the lowest all-cause mortality. I take 4,000 IU of vitamin D a day because that is the tolerable upper intake and it is quite safe.”
How Micronutrients & Exercise Ameliorate Aging | Dr. Rhonda Patrick
9:5614 references in 11 episodes from 2013–2025
Rhonda Patrick is a strong advocate for vitamin D3 supplementation, citing its role in immune function, longevity, telomere length, and gene regulation. She takes it daily, monitors her blood levels quarterly, and recommends maintaining levels between 40-60 ng/mL. No cautions or reasons to stop taking it were discussed.
Consumption
She takes 4,000 IU of vitamin D3 daily with vitamin K2, maintaining blood levels around 50-54 ng/mL, which she monitors quarterly.
Benefits
Vitamin D activates the innate immune system, regulates ~5% of the human genome, and is linked to longer telomeres, lower epigenetic age, and reduced all-cause mortality — with an optimal range of 40-60 ng/mL.
Best Practices
Vitamin D3 is preferable to D2, should be taken with fat for better absorption, and 4,000 IU/day is the tolerable upper intake considered quite safe.
“I think most physicians would agree that supplementing with anywhere from 1,000 to 2,000 IU of vitamin D per day is probably safe for most people and will buffer that level of vitamin D in their system such that they're unlikely to be deficient.”
How to Prevent & Treat Colds & Flu
1:47:134 references in 3 episodes from 2021–2024
Huberman takes vitamin D3 daily as part of his core supplement stack. He recommends 1,000–2,000 IU per day as a safe dose for most people to avoid deficiency, citing evidence that vitamin D deficiency impairs immune function and increases susceptibility to respiratory infections. No cautions or upper-limit warnings are discussed.
“If you don't have enough vitamin D, you'll get about a quarter of the calcium absorption through your gut that you would if vitamin D is sufficient. Your bone cells actually directly have vitamin D receptors on them, so there's a direct action there as well.”
Build Stronger Bones at Every Age
12:545 references in 4 episodes
Galpin emphasizes vitamin D as essential for bone health and brain function, highlighting its role in calcium absorption and its direct action on bone cells. He views it as a foundational micronutrient to optimize rather than a performance enhancer, noting it likely won't help if levels are already sufficient. There is no evidence of personal use, no specific dosing guidance, and no cautions discussed.
Benefits
Galpin identifies vitamin D as critical for calcium absorption (deficiency reduces gut absorption by ~75%) and bone health via direct vitamin D receptors on bone cells. He also considers it essential for brain function and notes an association between low vitamin D and reduced heart rate variability.
Side Effects
- Hypercalcemia at very high doses
- Nausea or appetite loss with excess intake
- Kidney stones with prolonged high-dose use
- Elevated blood calcium causing fatigue or confusion
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