Natto: the primary source of vitamin K2 and the solution to the calcium paradox¶
Vitamin K2 is crucial because of a phenomenon known as the “Calcium Paradox” — people who have excess calcium in their arteries (increased risk of heart attack) while simultaneously lacking calcium in their bones (osteoporosis).
Vitamin K2 resolves this problem:
- It removes calcium from where it causes trouble: Prevents arteries from becoming rigid like “stone pipes”.
- It puts it where it is needed: Builds a strong skeleton.
Why are we often deficient?¶
Unlike vitamin K1 (easy to obtain from salads), K2 is scarce in the modern Western diet because:
-
It is found in fermented foods that we no longer consume regularly (such as traditionally fermented sauerkraut or natto).
-
It is found in the fats of animals that eat grass. Most animals today are grain-fed, so their meat and dairy contain very little K2.
Vitamin K2 (menaquinone) is more difficult to obtain on a vegetarian diet than K1,
as it is produced mainly through bacterial fermentation.
While K1 is abundant in leafy green vegetables, K2 is found naturally in fermented foods and in some animal-derived products, such as dairy and eggs.
Sources of Vitamin K2¶
| Food | Category | Approximate Content (µg/100g) | Main Form |
|---|---|---|---|
| Natto | Plant-based (Fermented) | 850 – 1100 | MK-7 |
| Goose Liver Pâté | Animal Organ | 369 | MK-4 |
| Chicken Liver | Animal Organ | 13 – 150* | MK-4 |
| Beef Liver | Animal Organ | 11 – 106* | MK-4 |
| Aged Cheeses (Münster, Gouda, etc.) | Dairy | 50 – 80 | MK-8, MK-9 |
| Eel | Fish | 63 | MK-4 |
| Soft Cheeses (Brie, Camembert) | Dairy | 35 – 60 | MK-8, MK-9 |
| Egg Yolk (Pasture-Raised) | Egg | 15 – 32 | MK-4 |
| Butter | Dairy Fat | 15 | MK-4 |
| Miso / Tempeh | Plant-based (Fermented) | 10 – 30 | MK-7 |
| Sauerkraut / Kimchi | Plant-based (Fermented) | 2 – 5 | MK-7 |
- Natto is the “King”: By far the richest source of K2 in the world. It is a Japanese food made from soybeans fermented with the bacterium Bacillus subtilis. Just one tablespoon can cover daily requirements.
- The importance of fermentation: Vitamin K2 does not naturally exist in plants; it appears when they are fermented by specific bacteria (as in sauerkraut or kimchi), although in much smaller amounts than in natto.
- Internal conversion: The human body can convert a small portion of vitamin K1 (from spinach or broccoli) into K2, but this process is inefficient. For this reason, direct sources are recommended.
- Bioavailability: The MK-7 form (found in natto and other fermented foods) remains in the bloodstream for longer and is more effective for bone and cardiovascular health than the MK-4 form (found in eggs and butter).
Vitamin K2 is the body’s “traffic controller” for calcium. While vitamin K1 is mainly responsible for blood clotting in the liver, K2 works in peripheral tissues (bones and arteries) to ensure that calcium is deposited where it belongs and not where it can cause harm.
Below is a detailed explanation of its role and why it is so critical for your health:
The Essential Function: Activation of Gla Proteins¶
The importance of vitamin K2 lies in the fact that it is the only vitamin capable of activating (carboxylating) two essential proteins that regulate calcium. Without vitamin K2, these proteins remain “asleep” (inactive), and calcium circulates freely throughout the body.
- Osteocalcin: This protein is responsible for “capturing” calcium from the bloodstream and firmly binding it into the matrix of bones and teeth.
- Matrix Gla Protein (MGP): This is perhaps the most vital role. Activated MGP prevents calcium from being deposited in artery walls, heart valves, and other soft tissues.
The Benefits¶
| Health Area | Specific Benefit | Why does it happen? |
|---|---|---|
| Bone Health | Prevention of osteoporosis and fractures. | K2 activates osteocalcin, improving bone density and mechanical strength. |
| Cardiovascular Health | Prevention of arteriosclerosis (calcification). | It activates MGP, which clears calcium from the arteries, keeping them flexible and youthful. |
| Dental Health | Stronger teeth, more resistant to decay. | It supports mineralisation of dentine, the hard tissue beneath the enamel. |
| Synergy with Vit. D3 | Optimisation of supplementation. | Vitamin D3 increases calcium absorption, but K2 ensures that this calcium does not accumulate in the arteries. |
| Metabolic Health | Improved insulin sensitivity. | There is evidence that activated osteocalcin helps regulate blood sugar levels. |
Important
If you are taking Calcium or Vitamin D3 supplements, Vitamin K2 is essential to prevent that extra calcium from damaging your heart.