Understanding Vitamin K2 and Its Forms
Vitamin K is an essential, fat-soluble nutrient that is vital for several bodily functions, most notably blood clotting and proper calcium metabolism. Unlike vitamin K1, which is abundant in leafy greens, vitamin K2 (menaquinone) is predominantly found in fermented foods and animal products. The amount and type of K2 can vary dramatically depending on the food source.
There are two primary forms of vitamin K2 found in food: MK-4 and MK-7. Understanding the difference is key to appreciating their dietary sources.
- MK-4 (Menaquinone-4): This is a shorter-chain form of K2 found almost exclusively in animal-based products. Sources include grass-fed animal fats, egg yolks, and organ meats. However, it has a shorter half-life in the body compared to MK-7, meaning it doesn't circulate for as long.
- MK-7 (Menaquinone-7): This is a longer-chain form produced through bacterial fermentation. It has a significantly longer half-life, allowing it to accumulate in the bloodstream and better reach tissues outside the liver, such as bones and arteries. The MK-7 form found in natto is particularly potent.
The Absolute Top Sources of K2
When asking which food has the most K2, the answer is undisputed: Natto. But for those unable to stomach this unique dish, several other powerful sources exist.
Fermented Food Sources
- Natto: This Japanese delicacy is made from fermented soybeans using Bacillus subtilis bacteria and is the most potent source of MK-7 by a huge margin. A 100-gram serving can provide over 1000 mcg of vitamin K2.
- Aged Cheeses: Hard and soft aged cheeses are excellent sources of longer-chain menaquinones (MK-8 and MK-9). Gouda, Brie, Edam, and certain Swiss varieties are particularly high in K2 due to bacterial fermentation.
- Sauerkraut: While not as rich as natto, fermented cabbage contains small amounts of K2 produced by probiotic bacteria.
Animal-Based Food Sources
- Goose Liver Pâté: This is the most concentrated animal-based source of the MK-4 form of vitamin K2. Just 100 grams can contain up to 369 mcg, making it a very rich option.
- Organ Meats: Other organ meats, such as chicken and beef liver, are also significant sources of MK-4. Pan-fried chicken liver offers a decent amount of K2.
- Egg Yolks: Especially those from pasture-raised chickens, are a great source of MK-4. The egg yolk contains significantly more K2 than the egg white.
- Grass-Fed Butter: The fat from grass-fed dairy contains the MK-4 form of vitamin K2. Choosing products from pasture-raised animals is crucial, as their diet directly influences the K2 content.
Comparison of K2 Content in Key Foods
To provide perspective, here is a comparison table of the approximate vitamin K2 content in 100-gram servings of various foods:
| Food Source | Primary K2 Form | Approx. K2 Content (µg/100g) |
|---|---|---|
| Natto | MK-7 | 1000+ |
| Goose Liver Pâté | MK-4 | 369 |
| Aged Gouda Cheese | MK-9 | 76.3 |
| Brie Cheese | MK-9 | 56.5 |
| Egg Yolks (Pasture-Raised) | MK-4 | 32.1 |
| Grass-Fed Butter | MK-4 | 15.0 |
| Chicken Liver (Pan-Fried) | MK-4 | 12.6 |
Health Benefits of a K2-Rich Diet
Beyond simply answering which food has the most K2, it's important to understand why this vitamin is so essential. Its primary role involves working with other vitamins, particularly vitamin D, to regulate calcium in the body.
Bone Health
Vitamin K2 activates osteocalcin, a protein that binds calcium to the bone matrix, thereby enhancing bone strength and reducing the risk of fractures. This process is vital for preventing osteoporosis, especially in postmenopausal women.
Cardiovascular Health
K2 also activates Matrix Gla-Protein (MGP), which inhibits calcium from depositing in arteries and soft tissues. This helps prevent the vascular calcification that contributes to heart disease and high blood pressure.
Synergy with Vitamin D
For optimal calcium regulation, vitamin K2 and vitamin D work synergistically. Vitamin D enhances calcium absorption from the gut, while K2 ensures that this calcium is properly utilized in bones and kept out of arteries. You can find a useful fact sheet on vitamin K from the National Institutes of Health(https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/).
Conclusion
For those seeking the most concentrated source of K2, natto is the clear winner, offering high levels of the bioavailable MK-7 form. For those who cannot consume natto, excellent animal-based sources like goose liver pâté and pasture-raised egg yolks provide the MK-4 form, while aged cheeses offer various other menaquinones. Incorporating a variety of these foods into your diet is the best way to ensure optimal K2 intake for robust bone and cardiovascular health. Always consider dietary variety and consult with a healthcare provider for personalized advice, especially if you have existing health conditions or take blood-thinning medications.
