Evidence brief · Supplement
Vitamin D for Cancer / CVD prevention (replete adults)
Evidence grade D — VITAL and others null
- Overall grade
- Grade D
- Last revised
- 1
- graded outcome
- 2
- references listed
Assembled by the app from other entries in this library. It adds no evidence of its own — follow the links to the entries it draws on.
1 at grade D — 1 graded row
What is known
Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.
- Cancer / CVD prevention (replete adults)Evidence grade D
VITAL and others null
Trivialhigh
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Thin evidence: Cancer / CVD prevention (replete adults) (grade D).
The evidence in words
The verdict
For cancer / cvd prevention (replete adults), Vitamin D earns evidence grade D (trivial effect, high consistency) — the evidence does not support the claim. VITAL and others null
How it might work
Calcitriol regulates the transcription of hundreds of genes, most importantly those controlling intestinal calcium and phosphate absorption and bone remodeling. It also modulates immune-cell behavior, which is the mechanistic hook behind the (largely unproven) claims about infections and autoimmunity. Blood 25(OH)D is a storage marker; the body tightly controls how much active calcitriol it makes from it.
How to use it
Dose against a blood level, not a calendar. 1,000–2,000 IU/day maintains most adults; frank deficiency often needs 4,000 IU/day for 8–12 weeks then a re-test. Take it with the largest fatty meal of the day for absorption. Pair with vitamin K2 and adequate magnesium, both cofactors for putting the mobilized calcium where it belongs.
Safety & cautions
Very safe in the ordinary range; toxicity (hypercalcemia) is real but requires sustained megadosing, typically well above 10,000 IU/day for months. The classic mistake is high-dose D without magnesium (a required cofactor) or K2 (which directs calcium to bone rather than arteries).
Bottom line
If you live away from the equator, get a 25(OH)D test. If you're low, 1,000–2,000 IU/day with a fatty meal, K2 and magnesium alongside, re-test at 12 weeks. If you're already replete, more does nothing — the megadose-prevents-everything story did not survive the big trials.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Maintenance
- 1,000–2,000 IU (25–50 µg) D3 daily with a fatty meal.
- Repletion
- 4,000 IU/day for 8–12 weeks against a low 25(OH)D, then re-test.
- Cofactors
- Take with vitamin K2 (MK-7 90–180 µg) and ensure magnesium sufficiency.
Goes with
- Vitamin DRead the full Vitamin D monographEvidence grade A
Related reading
Entries that share this one's tags or conditions.
- Vitamin D for Autoimmune diseaseEvidence grade C — VITAL hinted at a small reduction; not establishedEvidence grade C
- Vitamin D for Correcting deficiency (25(OH)D)Evidence grade A — Dose-dependent, predictable riseEvidence grade A
- Vitamin D for Fracture / fall risk (deficient elderly + calcium)Evidence grade B — Benefit concentrates in the deficient and institutionalizedEvidence grade B
- Vitamin D for Osteoporosis / bone lossEvidence grade B — With calcium, in deficiencyEvidence grade B
Sources
As this entry records them: title, journal and year. None carries a DOI or PubMed id, so none is linked as a verified paper. Each link searches PubMed for the title; check that what you find is what the entry describes.
- 1.Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL) — N Engl J Med, 2019. Search PubMed (opens in a new tab)
- 2.Vitamin D and type 2 diabetes prevention (D2d) — N Engl J Med, 2019. Search PubMed (opens in a new tab)
Last revised . A grade is this entry's reading of the evidence, not medical advice.