Understanding Vitamin K2: MK-4 vs. MK-7
Vitamin K2, or menaquinone, is a group of fat-soluble vitamins with several subtypes. The two most prominent are menaquinone-4 (MK-4) and menaquinone-7 (MK-7), which are derived from different food sources and have varying effects on the body. Understanding this distinction is key to optimizing your intake.
MK-4: The Animal-Derived Form
MK-4 is a shorter-chain menaquinone found in animal products. It is produced by the conversion of K1 in animal tissues and is the form of vitamin K found in the brain, pancreas, and arterial walls. The MK-4 content of animal products is significantly influenced by the animal's diet. Grass-fed animals, which consume vitamin K1-rich grass, produce meat and dairy with much higher MK-4 levels than those fed grains.
Excellent MK-4 sources include:
- Goose liver pate, one of the richest sources, with very high concentrations.
- Organ meats such as beef and chicken liver.
- Egg yolks, particularly from pasture-raised chickens.
- Grass-fed butter and hard cheeses like Emmental.
- Dark poultry meat, especially chicken thigh with skin.
- Fatty meats like pork and beef from grass-fed animals.
MK-7: The Fermented Food Source
MK-7 is a longer-chain menaquinone produced during bacterial fermentation. It is known for its longer half-life in the body, meaning it stays active for a longer period compared to MK-4.
Primary MK-7 sources include:
- Natto (fermented soybeans): This Japanese dish is by far the richest food source of vitamin K2, specifically the MK-7 subtype, with some estimates reporting very high amounts per 100g.
- Some hard and soft cheeses: Certain bacterial cultures used in the fermentation of cheeses like Gouda, Brie, and Munster produce menaquinones, including MK-7, though the amount is much lower than in natto.
- Sauerkraut: This fermented cabbage contains some K2 from the bacteria involved in its creation.
Comparison of Key Vitamin K2 Sources
The table below outlines the vitamin K2 content of several key foods, highlighting the disparity between sources, particularly natto and other options. Values are approximate and can vary based on processing and origin.
| Food Source | Main K2 Form | Approx. K2 Content (μg per 100g) | Notes |
|---|---|---|---|
| Natto | MK-7 | High | Unmatched concentration due to specific fermentation process. |
| Goose Liver Pate | MK-4 | High | A rich source, but from a less common food item. |
| Aged Gouda Cheese | MK-7, MK-9 | Moderate | Content varies by type, aging, and fat content. |
| Beef Liver | MK-4 | Moderate | High in MK-4, but depends on the animal's diet. |
| Chicken (Dark Meat) | MK-4 | Moderate | Content is higher in grass-fed, pasture-raised birds. |
| Egg Yolk (Pasture-Raised) | MK-4 | Moderate | Content varies greatly based on hen's diet. |
| Sauerkraut | Mixed | Lower | Contains lower but still notable levels. |
Practical Ways to Incorporate Vitamin K2 into Your Diet
Including foods rich in vitamin K2 can be a manageable part of a balanced diet, even if some of the richest sources are not staples in your region. For those who enjoy dairy and meat, prioritizing grass-fed, full-fat options will significantly increase your MK-4 intake. For vegetarians and vegans, fermented foods become the primary avenue for obtaining K2.
Dietary Strategies
- Embrace Fermented Foods: While natto has a unique, potent flavor, fermented foods like certain cheeses and sauerkraut offer a more familiar way to get some K2. Consider adding aged Gouda or Brie to your diet, or making your own fermented vegetables. Note that most dairy products contain lower concentrations of K2 compared to natto.
- Choose Grass-Fed: When purchasing meat, dairy, and eggs, opt for products from grass-fed animals. Their diet naturally leads to higher levels of MK-4. Even butter from grass-fed cows can be a decent source.
- Include Organ Meats: If you're open to it, organ meats like chicken or beef liver are potent sources of MK-4 and many other vital nutrients.
- Partner with Fat: Since vitamin K2 is fat-soluble, consuming it with a source of dietary fat can enhance absorption. For example, adding some healthy fats to your fermented dishes can improve the bioavailability of the vitamin.
The Synergy with Other Nutrients
It is crucial to understand that vitamin K2 doesn't work in isolation. It has a synergistic relationship with other vitamins and minerals, especially Vitamin D and calcium. Vitamin D helps the body absorb calcium, while K2 activates the proteins (like osteocalcin and Matrix Gla Protein) that direct this calcium to the right places, such as your bones, and prevents it from depositing in soft tissues like arteries. This teamwork is essential for both skeletal and cardiovascular health.
Conclusion: Making Informed Choices for Optimal Health
For those seeking to improve their intake of vitamin K2 through diet, a combination of fermented foods and high-quality animal products is the most effective strategy. While natto remains the single most concentrated source, incorporating grass-fed dairy, egg yolks, and organ meats can provide a substantial amount of the MK-4 form. For vegans, natto is a unique and potent source, and while other fermented plant foods contain smaller amounts, supplements might be considered. The key is to be mindful of your food sources, opting for nutrient-dense options where possible. Ultimately, ensuring adequate vitamin K2 intake, alongside a balanced diet rich in other synergistic nutrients, is a valuable step toward supporting long-term bone and heart health.
For more detailed nutritional information on how vitamins like K2 work, consult authoritative sources on dietary supplements and health, such as the National Institutes of Health..
