What is Vitamin K2 and Why Does It Matter?
Before exploring the richest sources, it's helpful to understand what vitamin K2 is. Vitamin K is a fat-soluble vitamin crucial for several physiological processes, primarily blood clotting and calcium metabolism. It exists in two main forms: vitamin K1 (phylloquinone), found predominantly in leafy greens, and vitamin K2 (menaquinone), found in animal and fermented foods. The two forms play different roles in the body, with K2 being particularly important for directing calcium to the bones and teeth and away from soft tissues like arteries, which helps prevent vascular calcification.
Vitamin K2 is further broken down into subtypes, with the two most common being MK-4 and MK-7. MK-4 is found in animal products like eggs and meat, while MK-7 is primarily the result of bacterial fermentation. The concentration and type of K2 can vary significantly based on the source, which is why a diverse diet is key to adequate intake.
The Undisputed Champion: Natto
For those seeking the absolute highest dietary concentration of vitamin K2, the answer is natto. This Japanese food, made from fermented soybeans, is an unparalleled source of the MK-7 form of K2. Its high content is a direct result of the fermentation process driven by Bacillus subtilis bacteria.
While natto's strong smell and slimy texture can be an acquired taste for Western palates, even a small serving can provide a substantial amount of K2, often exceeding daily recommendations. For those willing to embrace this unique food, it can be a dietary game-changer for bone and heart health, as studies in Japan have shown a correlation between natto consumption and improved bone density.
Animal-Based Sources of Vitamin K2 (MK-4)
For those who find natto unappealing, or who prefer animal-based sources, several foods offer significant amounts of vitamin K2, specifically the MK-4 variant.
- Goose Liver Pâté: Among animal products, goose liver is an exceptional source of MK-4, though it is not a common part of most Western diets.
- Other Organ Meats: Beef and chicken liver also provide considerable amounts of K2. For instance, a 100-gram serving of beef liver offers over 100 mcg of K2.
- Pasture-Raised Eggs: Egg yolks are a reliable source of MK-4, but the vitamin K2 content is highly dependent on the chicken's diet. Eggs from pasture-raised hens, which forage on grass, contain significantly more K2 than those from conventionally raised, grain-fed hens.
- Meat: Chicken meat, especially the dark meat like thighs and wings, contains decent amounts of MK-4. Some processed meats like salami and certain cured products also contain K2, but these often come with other nutritional drawbacks like high sodium and saturated fat.
- Grass-Fed Butter: Butter from cows that graze on grass is another source of MK-4. The K2 content of butter is influenced by the animal's diet, similar to eggs.
Fermented Dairy and Cheeses (MK-8 and MK-9)
Many dairy products, particularly fermented ones, are excellent sources of different menaquinone subtypes (MK-8 and MK-9), which are also vital for bone health.
- Hard and Soft Cheeses: Cheeses like Gouda, Edam, Camembert, and Swiss are known to contain significant amounts of vitamin K2. The concentration of K2 in cheese increases with age, with some types like aged Gouda having higher levels than cheddar.
- Kefir: This fermented milk drink is a good source of K2, along with beneficial probiotics that support gut health. A healthy gut microbiome can also produce small amounts of K2.
- Sauerkraut: While not as potent as natto, fermented cabbage like sauerkraut can provide a modest amount of vitamin K2.
Understanding the Different Forms of Vitamin K2
It's important to recognize the different forms of K2, as their source and concentration differ widely. This table compares some of the most concentrated food sources.
| Food Source (per 100g) | Main K2 Form | Typical Vitamin K2 Content (μg) | Notes |
|---|---|---|---|
| Natto (fermented soybeans) | MK-7 | ~1,000 | Richest source, with high MK-7 concentration. |
| Goose Liver Pâté | MK-4 | ~369 | High MK-4 content from animal source. |
| Hard Cheeses (e.g., Gouda, Edam) | MK-8, MK-9 | ~76 | MK concentration varies by cheese type and age. |
| Soft Cheeses (e.g., Brie, Camembert) | MK-8, MK-9 | ~56 | Lower overall K2 than hard cheeses, also variable. |
| Egg Yolk (pasture-raised) | MK-4 | ~30-60 | Content depends heavily on the hen's diet. |
| Chicken Thigh (cooked) | MK-4 | ~53 | One of the better meat sources of K2. |
Tips for Maximizing Vitamin K2 Absorption
Since vitamin K is fat-soluble, its absorption is enhanced when consumed with a source of fat. Therefore, pairing your vitamin K2-rich foods with healthy fats is a smart dietary strategy. For instance, enjoying cheese with nuts or preparing eggs with a little grass-fed butter can increase bioavailability. For those incorporating natto, mixing it with rice and a little sauce or oil is a common practice.
Conclusion
While natto is the clear winner for what food has the most vitamin K2?, a balanced dietary approach that includes a variety of high-K2 foods is the most realistic path to optimal intake for most people. Combining fermented products with animal sources from pasture-raised animals ensures a good balance of both MK-4 and MK-7 forms. Understanding the different sources allows for informed choices that can positively impact long-term bone and heart health.
For more detailed nutritional information and health advice, consulting a healthcare professional or a registered dietitian is always recommended. Check out this article on dietary sources of K2 from Healthline for additional reading and health information.
