How Much Vitamin K2 Does Sauerkraut Actually Contain?

Sauerkraut is fermented cabbage, and cabbage is not a meaningful source of vitamin K2. The amount in sauerkraut is negligible — close to zero in most cases. If you are eating sauerkraut hoping to hit a vitamin K2 target, you are looking in the wrong place.

Vitamin K2 is a family of compounds called menaquinones. The main dietary sources are animal foods and fermented foods made by specific bacteria. Cabbage fermentation does not reliably produce these compounds in any useful amount. Some fermented foods do contain K2 — but sauerkraut is not one of them.

What Is Vitamin K2 and How Is It Different From Vitamin K1?

Vitamin K is not one substance. It is a group of fat-soluble compounds with a shared chemical ring but different tails. That difference matters for where they go in the body and what they do.

Vitamin K1, also called phylloquinone, comes mainly from green leafy vegetables. It is the form your liver uses to activate clotting factors. A deficiency in K1 causes bleeding problems, which is why newborns receive a vitamin K injection at birth.

Vitamin K2 refers to menaquinones, written as MK-4 through MK-13 depending on the length of the side chain. MK-4 is found in animal products like butter, egg yolk, and liver. MK-7, MK-8, and MK-9 are produced by certain bacteria during fermentation.

Vitamin K2 is also made in the human gut by bacteria. How much of that production the body actually absorbs and uses is still debated. The colon absorbs some, but the evidence on how much this contributes to vitamin K status is not settled.

Both K1 and K2 activate proteins that depend on vitamin K. But they differ in how long they stay in the blood and which tissues they reach. MK-7 has a longer half-life than K1, which is one reason it has drawn research interest for bone and artery health.

How Much Vitamin K2 Does Sauerkraut Actually Contain?

There is no reliable USDA database value for vitamin K2 in sauerkraut because the amount is too low and too variable to be useful. Standard food composition tables list vitamin K as K1 only. When researchers have measured menaquinones in sauerkraut, they have generally found little to none.

The bacteria that drive cabbage fermentation — mainly Leuconostoc and Lactobacillus species — are not the same bacteria that produce MK-7 in natto. Natto, fermented soybeans, is the richest known food source of MK-7. The Bacillus subtilis used to make natto produces large amounts of it. Cabbage fermentation does not.

Small amounts of MK-4 and longer-chain menaquinones have been detected in some sauerkraut samples. The key word is small. The variation between batches, brands, and fermentation methods is wide enough that no meaningful average can be given.

If you see a product label claiming a specific vitamin K2 content in sauerkraut, treat that number with caution unless the manufacturer provides third-party lab testing. Most sauerkraut labels do not list vitamin K2 at all, because it is not there in a measurable amount.

Which Foods Actually Contain Vitamin K2?

The foods with meaningful vitamin K2 content fall into two groups: animal foods with MK-4, and fermented foods with MK-7 and related menaquinones.

• Natto — fermented soybeans, the richest known source of MK-7 by a wide margin
• Hard aged cheeses — particularly Gouda, Edam, and similar varieties, which contain MK-8 and MK-9
• Egg yolk — MK-4
• Liver — particularly goose and chicken liver, MK-4
• Butter and full-fat dairy — MK-4, though amounts vary with what the animal ate
• Some fermented soy products — miso and tempeh contain smaller amounts than natto

Grass-fed animal products tend to have more MK-4 than conventional ones, because the animals convert K1 from grass into MK-4. But “more” is relative. The amounts in dairy and eggs are still modest compared to natto.

This is why the food source matters so much. Someone eating natto regularly gets a substantial dose of MK-7. Someone eating sauerkraut regularly is getting probiotics, fiber, and vitamin C — real benefits — but not vitamin K2.

Does Fermenting Cabbage Destroy or Create Vitamin K2?

Neither happens in a meaningful way. Fermentation does not create vitamin K2 in cabbage, and it does not destroy vitamin K1 either.

Cabbage starts with vitamin K1, not K2. The bacteria that ferment it do not convert K1 into K2. That conversion happens in animals, not in a fermentation crock. When a cow eats grass, its gut bacteria and tissues convert K1 to MK-4. That is a biological process inside an animal, not something that occurs during vegetable fermentation.

What fermentation does change in cabbage is worth noting. It increases available B vitamins, particularly B12 in some preparations, and it produces lactic acid that acts as a natural preservative. It also breaks down some of the plant compounds that make raw cabbage harder to digest.

Vitamin K1 in sauerkraut is actually fairly stable. A serving of sauerkraut still provides some vitamin K1 — the clotting-related form. That matters for people on blood-thinning medication, who need consistent vitamin K intake. The K1 content of sauerkraut is not zero, even though the K2 content is.

Why Do People Think Sauerkraut Contains Vitamin K2?

The confusion comes from lumping all fermented foods together. Natto is fermented and rich in K2. Kimchi is fermented cabbage. Sauerkraut is fermented cabbage. It seems logical that they would all be similar.

They are not. The specific bacterial strains determine what gets produced. Bacillus subtilis in natto makes MK-7. The lactic acid bacteria in sauerkraut and kimchi do not produce it in significant amounts. The fermentation method is similar; the microbiology is not.

There is also a broader pattern in wellness marketing of attaching health benefits to fermented foods as a category. Probiotics, K2, enzymes, and improved digestion all get mentioned together as if they come as a package. They do not. Each fermented food has its own nutrient profile, and the K2 content varies enormously depending on which bacteria did the fermenting.

A related point: some people assume that any food containing bacteria must produce vitamin K2, because gut bacteria make it. But the bacteria in a fermentation jar are not the same as the bacteria in the colon, and the conditions are different. Production in a jar does not follow the same rules as production in the gut.

Should You Take a Vitamin K2 Supplement Instead?

Whether to supplement is a decision to make with a clinician, not from an article. The evidence on vitamin K2 supplements is genuinely mixed, and it depends heavily on what outcome you are asking about.

For bone health, some studies suggest MK-7 may support bone mineral density, and research from Japan has looked at MK-4 for osteoporosis. But results across trials are not consistent, and the effect sizes in Western populations have generally been smaller than in Japanese trials. The reasons for that difference are not fully understood.

For cardiovascular health, the picture is even less clear. Observational studies have linked higher K2 intake to lower arterial calcification. But observational data cannot show cause and effect, and randomized controlled trials of K2 supplementation for cardiovascular outcomes have not produced consistent results.

What is well established: vitamin K interacts with warfarin and other vitamin K antagonist blood thinners. Anyone on these medications should not change vitamin K intake — from food or supplements — without talking to their prescriber first. This applies to sauerkraut’s K1 content and to any K2 supplement.

Vitamin K2 supplements are generally described as well tolerated in the research literature. That is not the same as proven effective for any specific outcome. If a product claims to direct calcium into bones and out of arteries, that claim is based on mechanism, not on demonstrated clinical benefit in large trials.

The Bottom Line on Sauerkraut and Vitamin K2

Sauerkraut is a good food. It provides probiotics, fiber, vitamin C, and vitamin K1. It does not provide vitamin K2 in any amount worth counting.

If vitamin K2 is your goal, natto is the food with by far the highest known content. Hard aged cheeses, egg yolks, liver, and butter are meaningful sources. Sauerkraut is not on that list, and no amount of it will change that.

Eat sauerkraut for what it actually offers. Get vitamin K2 from foods that actually contain it.