Vitamin K2 is found primarily in fermented foods, animal products, and certain cheeses. Unlike vitamin K1, which is abundant in leafy greens, K2 (also called menaquinone) is produced by bacteria during fermentation or created in the bodies of animals that convert K1 from their diet. The richest source by far is natto, a Japanese fermented soybean dish, but plenty of more familiar foods contain meaningful amounts.
Natto: The Richest Known Source
Natto stands alone as the most concentrated food source of vitamin K2. It’s made by fermenting soybeans with a specific strain of bacteria that produces large quantities of the MK-7 form of K2, which stays active in the body longer than other forms. A single serving delivers far more K2 than any other food. The catch is that natto has a strong flavor and sticky, stringy texture that many people outside Japan find challenging. If you can tolerate it, even a small daily portion provides a substantial dose.
Cheese and Dairy
Cheese is one of the most practical K2 sources for Western diets. The bacteria used in cheesemaking produce various forms of menaquinone during the aging and ripening process. Hard and aged European cheeses like Gouda, Edam, and Jarlsberg tend to have higher K2 levels than softer or fresher varieties. Brie contains a mix of K2 forms, with MK-4 being the most abundant at roughly 121 nanograms per gram of cheese.
The type of bacteria used in production matters. Different starter cultures produce different amounts and forms of K2, which is why K2 content varies significantly even between cheeses of the same style made by different producers. As a general rule, the longer and more complex the fermentation, the more K2 ends up in the final product.
Butter from grass-fed cows is notably richer in K2 than conventional butter. Cows eating fresh grass take in large amounts of vitamin K1, which their bodies convert to K2 (specifically the MK-4 form) and deposit into their milk fat. This same principle applies to other full-fat dairy products: the animal’s diet directly influences how much K2 ends up on your plate.
Egg Yolks
Egg yolks contain K2 in the MK-4 form, and the amount depends heavily on what the hen eats. Research on laying hens shows the range can be dramatic. Hens fed standard diets produce yolks with moderate MK-4 levels, while hens given vitamin K-enriched feed produced yolks containing anywhere from 67 to 240 micrograms of MK-4 per 100 grams of yolk. Pasture-raised eggs, where hens eat greens and insects rich in K1, generally contain more K2 than eggs from conventionally raised hens, though exact levels aren’t standardized.
Organ Meats and Poultry
Goose liver, particularly in the form of foie gras, is often cited as the highest animal-based source of K2 in the MK-4 form. Chicken liver and duck liver also contain significant amounts, though somewhat less than goose liver. Dark chicken meat, including thighs and legs, provides moderate K2 as well.
The pattern across animal products is consistent: organs and darker, fattier cuts contain more K2 than lean muscle meat. This is because MK-4 accumulates in tissues where fat metabolism is active. Beef liver contains some K2, but poultry livers tend to be richer sources.
Fermented Vegetables
Sauerkraut and kimchi both contain vitamin K2 thanks to the bacterial fermentation of cabbage. However, quantifying exactly how much K2 they deliver is difficult because it depends on the specific bacteria present, the length of fermentation, and storage conditions. These foods provide less K2 than natto, but they offer the added benefit of supporting gut health through their probiotic content, which may indirectly help with K2 status.
Other fermented foods like miso and tempeh also contain some K2, though again in variable amounts. The common thread is bacterial fermentation: wherever bacteria are actively breaking down and transforming food, some K2 production is likely occurring.
Your Gut Bacteria Make K2 Too
The bacteria living in your large intestine produce several forms of vitamin K2 as a byproduct of their normal metabolism. Different bacterial species make different forms. Bacteroides bacteria tend to produce longer-chain forms like MK-9 and MK-10, while Prevotella species are associated with MK-5 through MK-7. Research from the American Journal of Clinical Nutrition found that fecal K2 concentrations closely tracked the composition of a person’s gut microbiome.
How much of this bacterially produced K2 your body actually absorbs and uses remains an open question. Most of it is produced in the colon, where absorption of fat-soluble vitamins is limited. Scientists still haven’t determined whether gut-produced K2 meaningfully contributes to your daily needs, which means dietary sources remain important.
How Animal Diet Affects K2 Content
One of the biggest variables in K2 content is what the animal ate. Grass-fed and pasture-raised animal products consistently contain more K2 than their conventional counterparts. This applies across the board: butter, cheese, egg yolks, and meat all reflect the animal’s access to vitamin K1 from fresh plants. Animals convert dietary K1 into MK-4 in their tissues, so more K1 in means more K2 out.
This is why traditional diets that relied on pastured animals tended to be naturally higher in K2, and why the shift toward grain-fed livestock has reduced K2 in the modern food supply. If you’re specifically trying to increase your K2 intake through animal products, choosing grass-fed and pasture-raised options makes a real difference.
No Separate Recommendation for K2
There is currently no distinct recommended daily intake for vitamin K2. The NIH sets a single adequate intake for all forms of vitamin K combined: 120 micrograms per day for adult men and 90 micrograms for adult women. These numbers are based primarily on K1 intake data, and scientists acknowledge that insufficient data exist to set a more precise requirement, let alone a separate target for K2.
Because K2 is fat-soluble, eating it alongside dietary fat improves absorption. This happens naturally with most K2-rich foods since cheese, egg yolks, butter, and liver all contain fat. If you’re taking a K2 supplement, having it with a meal that includes some fat will help your body absorb more of it.