Sauerkraut contains roughly 5 mcg of vitamin K2 per cup, though the exact amount varies depending on how long it fermented and the bacterial strains involved. That’s a modest contribution compared to high-K2 foods like natto (which delivers over 1,000 mcg per serving), but sauerkraut is one of the more accessible fermented sources in Western diets.
Why K2 Amounts Vary in Sauerkraut
Vitamin K2 isn’t naturally present in raw cabbage. It’s produced by bacteria during fermentation. The specific strains of lactobacillus doing the work, the fermentation temperature, and how many weeks the sauerkraut sits all influence the final K2 content. Homemade sauerkraut that ferments for several weeks generally develops more K2 than a batch pulled after just a few days. Store-bought sauerkraut that has been pasteurized (heat-treated) still contains whatever K2 formed during fermentation, but the beneficial bacteria themselves are no longer alive.
A one-cup serving of sauerkraut provides about 19.6 mcg of total vitamin K, which covers roughly 16% of the daily value. Most of that total is vitamin K1, carried over from the cabbage itself. The K2 portion, produced by fermentation, makes up a smaller share of the total, typically in the range of 5 mcg per cup. A standard half-cup serving would contain roughly half those amounts.
K2 in Sauerkraut vs. Other Foods
To put sauerkraut’s K2 content in perspective, here’s how common food sources compare per typical serving:
- Natto (fermented soybeans): around 1,000 mcg per 3.5-ounce serving, by far the richest dietary source
- Hard cheeses (Gouda, Emmental): roughly 50 to 75 mcg per 3.5-ounce serving
- Soft cheeses (Brie, blue cheese): around 30 to 50 mcg per 3.5-ounce serving
- Egg yolks: approximately 5 to 10 mcg per yolk
- Sauerkraut: approximately 5 mcg per cup
- Chicken thigh (dark meat): roughly 5 to 10 mcg per 3.5-ounce serving
Sauerkraut falls on the lower end. If your primary goal is boosting K2 intake, aged cheeses and dark poultry meat are more concentrated everyday sources. Natto is in a category of its own but has a strong flavor that many people outside Japan find challenging.
How Much K2 Do You Actually Need?
There’s no official recommended intake specifically for vitamin K2. The adequate intake set by the National Institutes of Health covers total vitamin K (both K1 and K2 combined): 120 mcg per day for adult men and 90 mcg for adult women. Most people meet this through K1 in leafy greens without thinking about it.
K2 plays a different role than K1, though. While K1 is primarily involved in blood clotting, K2 helps direct calcium into bones and teeth and away from soft tissues like arteries. Research on bone density and cardiovascular health has used supplemental doses of K2 ranging from 45 to 200 mcg per day, well above what sauerkraut alone provides. Many nutrition researchers consider K2 an underappreciated nutrient precisely because official guidelines don’t yet distinguish between the two forms.
Getting More K2 From Your Sauerkraut
If you make sauerkraut at home, longer fermentation times (four to six weeks rather than one to two) give bacteria more opportunity to synthesize K2. Keeping the ferment at a cool, steady temperature around 65 to 72°F encourages slow, thorough fermentation. Using a diverse salt brine and clean equipment supports a healthy population of K2-producing bacteria.
When buying sauerkraut, look for unpasteurized versions sold in the refrigerated section. These still contain live cultures, which continue producing small amounts of K2 even in the jar. Shelf-stable canned sauerkraut has been heat-treated, so the K2 already present remains, but no new K2 is being generated.
Pairing sauerkraut with other K2-rich foods is a practical strategy. A meal with sauerkraut alongside eggs or cheese adds up faster than relying on any single source. Vitamin K2 is fat-soluble, so eating it with some dietary fat (which sauerkraut meals often naturally include) helps your body absorb it more efficiently.