Vitamin K1
The leafy-green vitamin K: essential, cheap, and oversold as a supplement.
C+
Evidence grade
C+
Worth it
$5-10/month
Typical cost
DoseAdequate intake is 90 mcg a day for women and 120 mcg for men, an amount a serving of leafy greens covers several times over. Supplements commonly sell 100 to 1,000 mcg; the one fracture-signal trial used 5 mg (5,000 mcg) a day, a pharmacologic dose, not a dietary one.
BasisAn essential nutrient with a thin supplement case.
Vitamin K1 (phylloquinone) is the dietary form of vitamin K, concentrated in leafy green vegetables and some plant oils. We grade Vitamin K1 C+ on evidence and C+ for worth-it at about $5-10 per month.
What it does
Vitamin K1 (phylloquinone) is the dietary form of vitamin K, concentrated in leafy green vegetables and some plant oils. It is essential for blood clotting and for activating proteins that manage calcium in bone. It is graded here as its own record beside vitamin K2: the forms share a vitamin family but not an evidence base, and K2 trial results do not transfer to K1.
What the research says
Required for normal blood clotting and bone protein activation
Evidence: strong. Established nutrient function; deficiency is rare in adults eating a normal diet, which is precisely why the supplement case is thin.
May reduce fracture risk at pharmacologic doses in postmenopausal women
Evidence: emerging. ECKO trial (Cheung et al., 2008): 5 mg a day, no bone-density effect, fewer clinical fractures on secondary analysis. One trial, one population, a dose far above dietary levels.
Higher intake is associated with slower cognitive decline
Evidence: emerging. Rush cohort analyses (Booth and colleagues): association between K1 status and cognition in older adults. Observational; no trial has tested K1 for cognition.
An essential nutrient with a thin supplement case. The best K1 trial (ECKO, 440 postmenopausal women, 5 mg a day) found no bone-density benefit and a fracture reduction only on a secondary analysis; cohort work links higher K1 status to slower cognitive decline, observational only. The strong Japanese bone data belong to MK-4, a K2 form, and are not counted here. Adequate intake from food is well supported; benefit from K1 pills beyond adequacy is not.
Is it worth it?
Evidence (C+) sits below the leaderboard floor, so the worth-it grade is capped at C+ however inexpensive it is. About $7.50 a month at a common dose. For most readers the better purchase is the food: leafy greens deliver K1 with the rest of the vegetable attached. Derived from the October 2026 worth-it model.
Typical cost
$5-10/month
Common form, not a brand recommendation
Dosage context established
Adequate intake is 90 mcg a day for women and 120 mcg for men, an amount a serving of leafy greens covers several times over. Supplements commonly sell 100 to 1,000 mcg; the one fracture-signal trial used 5 mg (5,000 mcg) a day, a pharmacologic dose, not a dietary one.
Worth-it leaderboard
Vitamin K1 sits outside the worth-it top 20.
Vitamin K1 sits outside the current top 20 on the gated leaderboard. The leaders below clear an evidence floor of B- before price counts at all, so cheap alone never earns a rank.
- 1AWorth itCreatine evidence A-~$5-10/mo
- 2AWorth itCaffeine evidence B+~$5-10/mo
- 3AWorth itVitamin D evidence B~$5-8/mo
See the full worth-it leaderboard →
When the evidence moves a grade, this ranking moves with it. Thursday is where you hear it first.
Safety notes
If you take warfarin or another vitamin K antagonist blood thinner, vitamin K1 is the interaction itself: it directly reduces the drug's effect, and K1 is the form clinicians use to reverse warfarin. Do not supplement it, and keep dietary intake consistent, unless your anticoagulation clinic directs it. Otherwise K1 is well tolerated, no tolerable upper level has been set, and food-level intake carries no known risk. This page is information, not medical advice.
Longevity Lab Report
Vitamin K1 news. Graded when it happens.
The grade on this page stays free. The email carries the news on Vitamin K1: expert moves, dose changes, and what is working, in plain English every Thursday.
Changelog
Last updated 2026-10-30
- 2026-10-30|Initial grading: vitamin K1 graded as its own record beside the graded K2 forms, per the 2026-10-27 shape ruling. The record grades the supplement case, not the nutrient's essential role: fracture signal C+ family on one trial's secondary analysis, cognition association observational, and the Japanese bone literature excluded because it tests MK-4, a K2 form. Goals are empty by design: the graded outcomes (bone density and fracture at dietary-relevant evidence, cognition association) map to no goal in the library taxonomy at graded strength, and the warfarin interaction is the record's safety centre.
The week's longevity and biohacking news.
This grade for Vitamin K1 rests on the record above. When a new result changes that record, the grade changes with it, and the Thursday email is where the change lands first: the week's longevity and biohacking news, in plain English, linked back to the reasoning on this page.
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Every grade follows a published rubric, and sponsors never change one. When the evidence moves a grade, Thursday is where you hear it first, before you renew a stack that stopped earning its cost.