Understanding the Different Forms of Vitamin K2
Vitamin K is a family of fat-soluble vitamins, primarily categorized into two main types: K1 (phylloquinone) and K2 (menaquinone). While K1 comes mainly from green leafy vegetables, natural K2 is found in fermented foods and animal products. The two primary subtypes of K2 are MK-4 and MK-7.
MK-4: The Animal-Derived Form
Menaquinone-4 (MK-4) is a short-chain K2 found mainly in animal fats. It can be made in the body from vitamin K1, but this is often not very efficient. The amount of MK-4 in animal products depends on the animal's diet, with grass-fed animals having more than grain-fed ones. MK-4 is active in various parts of the body, including the brain and heart.
MK-7: The Bacterial Form
Menaquinone-7 (MK-7) is a long-chain K2 mainly made by bacteria during fermentation. MK-7 stays in the body longer than MK-4 due to its longer half-life. This makes MK-7 potentially more effective for bone and heart health over time. Natto, a fermented soybean product, is the best natural source of MK-7.
The Richest Natural Food Sources of Vitamin K2
To get more vitamin K2, focus on foods rich in either MK-4 or MK-7. These foods also offer other health benefits.
Fermented Foods (High in MK-7)
- Natto: This Japanese fermented soybean dish is the top food source for MK-7. Even a small serving provides a lot of K2.
- Sauerkraut: Fermented cabbage like sauerkraut contains some K2 from the fermentation process. The amount varies depending on how it's made.
- Hard and Soft Cheeses: Certain fermented cheeses, especially hard and ripened soft types like Gouda and Brie, are good sources of vitamin K2, mainly MK-8 and MK-9.
- Kefir: This fermented milk drink offers probiotics and a small amount of K2.
Animal Products (High in MK-4)
- Goose and Chicken Liver: Organ meats are particularly high in MK-4. Goose liver pâté is one of the best sources.
- Pasture-Raised Eggs and Butter: The K2 content in eggs and butter is linked to the animals' diet. Products from grass-fed animals have more K2 than those from grain-fed ones.
- Fatty Meats: Fats from pasture-raised animals like beef and pork contain notable levels of MK-4.
Comparison of K2 Sources: Fermented vs. Animal Products
| Feature | Fermented Foods (Primarily MK-7) | Animal Products (Primarily MK-4) |
|---|---|---|
| Primary Source | Bacterial fermentation | Animal fat from diet conversion |
| Most Potent Example | Natto (extremely high) | Goose liver pâté (high) |
| Vegan/Vegetarian Option | Yes (e.g., natto, sauerkraut) | No |
| Bioavailability | High; longer half-life means it stays in the body longer | Lower; shorter half-life means it is cleared faster |
| Dietary Importance | Provides potent, sustained doses of MK-7 | Contains MK-4, which is active in multiple tissues |
| Fat Content | Generally lower (except for cheeses) | Higher (K2 is fat-soluble) |
| Accessibility | Varies; natto is not widely available | Readily available, but sourcing grass-fed requires effort |
Increasing Vitamin K2 in Your Gut
Besides diet, gut bacteria also produce menaquinones. A healthy gut microbiome supports this. Eating fermented foods like sauerkraut and kefir adds beneficial bacteria. Fiber from fruits and vegetables also helps maintain a healthy gut, supporting K2-producing bacteria.
Synergistic Nutrients and Dietary Tips
Vitamin K2 works well with vitamins A and D. Getting enough of all three is vital for calcium metabolism and bone health. Since K2 is fat-soluble, eating K2-rich foods with healthy fats helps absorption. For example, have cheese with olive oil or eggs with grass-fed butter.
Conclusion: A Balanced Approach to K2
To get vitamin K2 naturally, combine fermented foods and animal products. Natto is the best source of MK-7, while hard cheeses, sauerkraut, eggs, and organ meats are also good options. Eating these foods, supporting gut health, and getting enough vitamins A and D can improve your natural K2 levels, benefiting bone and heart health. Always consider your diet and health goals. If you have health issues or take blood thinners, talk to a doctor before changing your vitamin K intake.
For more detailed nutritional information and daily value percentages, you can consult authoritative resources like the National Institutes of Health (NIH): National Institutes of Health (NIH)
