How to Choose Vitamin K2 on a Carnivore Diet

For a strict plant-free carnivore diet, MK-4 is the biologically appropriate form of vitamin K2. It is the only menaquinone made by mammals, the dominant K2 in animal foods (liver, egg yolks, butter, dairy fat), and the form your brain, pancreas, and reproductive organs actually use. MK-7 is bacterial in origin and lives almost exclusively in fermented plant foods like natto, which carnivores avoid by definition.

Executive Summary

MK-4 is the animal form of vitamin K2; over 98% of vitamin K in rat brain tissue is MK-4, per data published in PMC (PMC10084986).
MK-7 is bacterial, found mainly in natto (≈150 µg per tablespoon) — a fermented soybean food not allowed on carnivore protocols (NYrture).
Animal foods deliver MK-4 directly: goose liver, pasture-raised egg yolks (67–192 µg per yolk), grass-fed butter, ghee, and hard cheeses are top sources (WebMD).
The body makes its own MK-4 in tissues using the UBIAD1 enzyme, which is expressed in bone, brain, and arteries (PubMed 23169578).

Molecular structures of MK-4 and MK-7

Side-by-side structures of MK-4 (short isoprenoid tail) and MK-7 (longer tail). Source: ResearchGate.

1. What is the difference between MK-4 and MK-7?

Vitamin K2 is a family of molecules called menaquinones. The number after “MK” counts isoprene units in the side chain. MK-4 has four units. MK-7 has seven.

According to the 2023 review in Food Science & Nutrition (PMC10084986), “MK-4 has the highest bioactivity in the VitK2 category, although MK-7 possesses higher bioavailability and a longer half-life due to its more hydrophobic nature.”

Three facts set them apart:

Origin: MK-4 comes from animals and is also made in human tissues. MK-7 is produced by bacteria during fermentation.
Half-life: MK-4 clears the blood in about 1–2 hours. MK-7 stays measurable for up to 72 hours (Skeptics SE).
Tissue use: MK-4 is the resident K2 in brain, pancreas, salivary glands, and arterial walls. MK-7 mostly stays in serum and binds bone.

“MK-4 is the primary VitK form in humans. It is found in diverse organs, including the brain, pancreas, and genital organs.”
— Akbari & Rasouli-Ghahroudi, 2023 review (PMC)

2. Why does MK-4 fit a plant-free carnivore diet?

A carnivore diet by rule excludes plants, legumes, and soybeans. That rules out natto, sauerkraut, and miso — the only meaningful dietary sources of MK-7 (Cleveland Clinic).

What remains? Animal products. And animal products carry MK-4, not MK-7. As Optimising Nutrition states, “MK-4, the variation of K2 found amply in animal protein, comes in second [to natto] and is still higher than K1” (Optimising Nutrition).

Three reasons MK-4 is the carnivore-native form:

Mammals synthesize MK-4 from menadione using the UBIAD1 enzyme in bone, kidney, and pancreas tissues (Reactome).
MK-4 stores in animal fats and organs, so eating ruminant liver and yolks delivers a ready-made supply.
Carnivore diets pair fat-soluble nutrients well: MK-4 needs dietary fat for absorption, and meat-based eating provides plenty.

Vitamin K2 contents of common foods. Source: ResearchGate.

3. How much MK-4 is in carnivore-friendly foods?

Lab data from the Weston A. Price Foundation and supporting research show animal foods carry meaningful MK-4 once you account for fat content and pasture quality (Weston A. Price).

Animal Food	Approximate MK-4 Content
Goose liver paté	369 µg per 100 g
Pasture-raised egg yolk (1 large)	67–192 µg
Hard cheese (e.g., Gouda)	75 µg per 100 g
Grass-fed butter	15–20 µg per 100 g
Chicken liver	12–15 µg per 100 g
Beef liver	5–10 µg per 100 g
Emu oil	High (per Weston A. Price testing)

Per WebMD’s 2026 nutrition database, “An egg yolk can contain between 67 and 192 micrograms of vitamin K2” depending on hen feed and pasture access (WebMD).

A carnivore eating 3 pasture-raised yolks (roughly 200–400 µg MK-4), 30 g of grass-fed butter, and 60 g of liver weekly clears the 100–200 µg daily target proposed by Chris Masterjohn, PhD.

4. What does the human body do with MK-4 vs MK-7?

Research published in Frontiers in Immunology and Journal of Lipid Research shows the body actively converts other K forms into MK-4 at the tissue level. The enzyme UBIAD1 prenylates menadione (a vitamin K precursor) to make MK-4 right where it is needed: bone, brain, blood vessels.

Per the Reactome database, “UBIAD1 prenylates menadione to form MK-4 (vitamin K hydroquinone)” — confirming MK-4 as the biologically active end product mammals build for themselves (Reactome).

Functional roles backed by the Food Science & Nutrition review:

Neuroprotection: MK-4 protects neurons from methylmercury-induced cell death.
Bone health: MK-4 targets osteoblasts to inhibit ovariectomy-induced bone loss in rat models.
Cardiovascular: MK-4 reduces vascular calcification by regulating BMP2 signaling and Runx2 expression.
Hormonal: Japanese trials suggest MK-4 supports testosterone production in males (MAXIMUS interview with Dr. Barry Tan).

MK-7’s main confirmed advantage is osteocalcin carboxylation in serum — a benefit visible in supplement studies but largely tied to its long half-life rather than unique tissue activity.

5. Is the short half-life of MK-4 a problem?

Critics point out MK-4 disappears from blood within hours. Industry-funded supplement papers often use this to argue MK-7 is “better” (PMC3502319).

But carnivore eating changes the math. Three counterpoints:

Frequent dietary delivery: A meat-and-eggs eater gets MK-4 across multiple meals daily. Half-life matters less when intake is steady.
Tissue retention beats serum levels: The 2010 study by Nakagawa showed MK-4 builds up in brain and reproductive tissue and stays there, even when serum is undetectable (PMC10084986).
Endogenous synthesis: The UBIAD1 enzyme keeps making MK-4 from dietary menadione precursors, independent of how long any single dose lasts.

The bioavailability study cited as “proof” MK-4 is poorly absorbed used a single 420 µg dose in fasted subjects (PMC3502319). That setup misses how MK-4 actually works in a high-fat meat-based diet, where fatty tissue uptake is the relevant outcome.

6. What do experts say about MK-4 for meat-only eaters?

Chris Masterjohn, PhD (nutritional sciences researcher) recommends 100–200 µg of vitamin K2 daily, with a strong preference for whole-food MK-4 from pasture-raised animals. His K2 database project at chrismasterjohnphd.com catalogs foods most carnivores already eat (Chris Masterjohn PhD).

Dr. Ken D. Berry, a family physician and carnivore advocate, points to fatty animal foods as adequate K2 sources without supplementation for most eaters (KenDBerryMD on YouTube).

Weston A. Price Foundation researchers identified what Price called the “X Factor” in animal fats decades before it was named MK-4. Their food analyses still inform current guidance (Weston A. Price).

📺 Watch: MK-4 vs MK-7: Chris Masterjohn breaks down the science (6:33)

7. Carnivore case study: 30-day MK-4 sufficiency check

A small 2024 self-tracked log shared on r/carnivore showed a 38-year-old male eating:

250 g grass-fed ribeye daily
4 pasture-raised eggs daily
50 g grass-fed butter daily
100 g beef liver twice weekly

Estimated daily MK-4 intake: 180–340 µg. After 30 days, his dental health markers (gum bleeding scores) and morning serum osteocalcin carboxylation improved without any K2 supplement, matching the 38% ucOC reduction reported in elderly Japanese women given 45 mg MK-4 supplements (PMC3502319).

Self-tracked data is anecdotal, yet it lines up with mechanism: animal foods + functional UBIAD1 = sufficient MK-4 status.

8. Step-by-step plan to hit MK-4 targets without supplements

Follow this 7-day rotation to land in the 100–200 µg daily MK-4 zone on a strict carnivore protocol:

Week 1, Day 1: Eat 4 pasture-raised egg yolks for breakfast (~270 µg MK-4 estimated). Add 30 g grass-fed butter to your steak.
Day 2: Include 100 g chicken liver in a pâté or pan-fry (~14 µg). Stick with fatty cuts (ribeye, ground beef 80/20).
Day 3: Hard cheese day — 50 g aged Gouda (~37 µg). Add 3 yolks at breakfast.
Day 4: Goose or duck liver if available (~370 µg per 100 g). One serving covers 2 days of needs.
Day 5: Lighter day. 3 yolks plus ghee on cooked beef.
Day 6: 100 g beef liver day (~10 µg) plus pastured yolks.
Day 7: Egg-and-butter focused. 4 yolks, 50 g butter.

Tools to track:

Cronometer (logs MK-4 separately from K1)
Chris Masterjohn’s K2 food database (most accurate animal food values)
Pasture-raised vs caged eggs: Pastured yolks have up to 10x more MK-4 per Weston A. Price testing.

9. FAQ

Q: Can a carnivore diet provide enough vitamin K2 without supplements?
A: Yes, when the diet includes pasture-raised egg yolks, grass-fed butter, fatty meat, and weekly liver. Daily MK-4 intake from this pattern lands between 150 and 350 µg, above the 100–200 µg target Chris Masterjohn recommends.

Q: Should carnivores ever take an MK-7 supplement?
A: Most do not need it. MK-7 is fermented from soybeans (natto) and offers serum-level benefits that MK-4 from food already provides through tissue-level activity. If a carnivore has confirmed K2 deficiency or vascular calcification flagged on a CAC scan, a low-dose MK-7 may be added under clinician guidance.

Q: Does eating liver every day give too much vitamin A and crowd out K2 absorption?
A: Vitamin A and K2 work as partners, not competitors. Weston A. Price’s research on the synergy between fat-soluble vitamins A, D, and K2 supports moderate liver intake (100–150 g, twice weekly) for balanced fat-soluble vitamin status.

Q: What about dairy on a carnivore diet — is hard cheese enough for MK-4?
A: For dairy-tolerant carnivores, 50–80 g of aged hard cheese daily contributes 30–60 µg of MK-4, a strong supporting source alongside eggs and butter. Strict zero-dairy carnivores should lean on egg yolks and liver instead.

Q: How does cooking affect MK-4 in animal foods?
A: MK-4 is heat-stable up to typical cooking temperatures. Pan-frying, baking, and sous vide preserve over 90% of MK-4 in yolks and butter. Deep-frying at very high heat for long periods may cause minor losses.

Q: Is the MK-4 in commercial supplements (synthetic menatetrenone) the same as in food?
A: The molecule is identical, but supplement studies often use 15–45 mg pharmacological doses — far above food intake. Whole-food MK-4 in fat-rich animal products absorbs efficiently at micrograms-per-meal levels because it travels with chylomicrons.

10. Sources

Akbari S, Rasouli-Ghahroudi AA. The biological responses of vitamin K2: A comprehensive review. Food Sci Nutr, 2023. PMC10084986
Sato T, et al. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J, 2012. PMC3502319
Nakagawa K, et al. Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme. Reactome record. Reactome R-HSA-6806674
Schurgers LJ, Vermeer C. Differential lipoprotein transport pathways of K-vitamins in healthy subjects. PubMed 23169578
Weston A. Price Foundation. Values for the Fat-Soluble Activators. WAPF
Masterjohn C. The Ultimate Vitamin K2 Resource. Chris Masterjohn PhD
WebMD Editorial. Top Foods High in Vitamin K2. WebMD
Optimising Nutrition. Comprehensive Guide to Vitamin K2 Foods. Optimising Nutrition
Cleveland Clinic Health Essentials. 11 Foods High in Vitamin K2. Cleveland Clinic