What do experts say about Vitamin D?

Mark Hyman: "The vitamin D deficiency is epidemic, with up to 80 percent of modern day humans being deficient or suboptimal in their intake." Also covered: Rhonda Patrick, Michael Greger, Peter Attia.

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Supplement

Vitamin D

Q: Is Vitamin D worth taking?

We grade Vitamin D A- for worth-it at a typical cost of $5-8 per month. DRAFT: cheap, deficiency is common and testable, and correction has clear benefits; grade reflects that non-deficient people likely gain little.

The deficiency is common. The hype is louder than the data.

Vitamin D is a fat-soluble vitamin the skin makes from sunlight and the body also gets from food and supplements. We grade Vitamin D B on evidence and A- for worth-it at about $5-8 per month.

Reference entry: kept for comparison, not a focus area

Evidence

A-

Worth it

Typical cost: $5-8/month

What it does

Vitamin D is a fat-soluble vitamin the skin makes from sunlight and the body also gets from food and supplements. It is essential for calcium absorption and bone health. Low blood levels are common, especially in winter and at northern latitudes.

What the research says

Supports bone health and corrects vitamin D deficiency
Evidence: strong. Established for bone mineralization and deficiency correction.
May support immune function
Evidence: moderate. Association data is strong; RCT evidence for supplementation preventing illness is mixed. Needs verification.
May support mood in deficient individuals
Evidence: emerging. Some trials suggest benefit when deficiency is corrected; not established for non-deficient people. Needs verification.

DRAFT: bone health and deficiency correction are well established; broader immune and mood claims are less settled, which caps the grade.

What the experts say

Every position links to its source. We include skeptics alongside supporters.

Mark Hyman
“The vitamin D deficiency is epidemic, with up to 80 percent of modern day humans being deficient or suboptimal in their intake.”
Source Calls vitamin D deficiency epidemic; recommends 2,000-5,000 IU/day of D3 with K2 and magnesium, targeting 50-75 ng/mL.
Rhonda Patrick
Source Takes about 4,000 IU/day of vitamin D3 total, targeting 40-60 ng/mL year round, calling supplementation an insurance policy because diet and modern indoor life leave most people short.
Michael Greger
Source Skeptical of broad vitamin D supplementation claims; frames the question around which conditions the supplement has actually been proven effective for in randomized, double-blind, placebo-controlled trials, implying a short list.
Peter Attia
Source Takes 5,000 IU/day but only reluctantly; he believes most vitamin D trials have been poorly done and is unconvinced supplementation matters much, taking it mainly because he sees the risks as minuscule.

Is it worth it?

A-

DRAFT: cheap, deficiency is common and testable, and correction has clear benefits; grade reflects that non-deficient people likely gain little.

Typical cost

$5-8/month

Common form, not a brand recommendation

Dosage contextestablished

1,000 to 2,000 IU per day is the common maintenance range; test blood levels first and dose to the result.

Safety notes

Vitamin D is fat-soluble, so very high doses can accumulate; more is not better. A blood test is the reliable way to know if you are deficient. Talk to your doctor about testing and dosing. This page is information, not medical advice.

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Changelog

Last updated 2026-10-15

2026-10-15|Seed entry created as DRAFT. Immune and mood claims marked needs verification.
2026-10-15|Flagged as reference entry: kept for comparison, not a focus area.
2026-10-15|Dosage context added.
2026-10-15|Goal tags added for the stack builder.
2026-10-15|Expert position sourced for Mark Hyman.