One tablespoon of natto powder is enough for 200% Vitamin K2, and I guess it tastes good enough (way better than supplements normally taste). “One tablespoon of Natto contains 150 micrograms of vitamin K2, about twice the recommended intake”
However, at least one published study concluded that “MK-4 present in food does not contribute to the vitamin K status as measured by serum vitamin K levels. MK-7, however significantly increases serum MK-7 levels and therefore may be of particular importance for extrahepatic tissues.”[3]
Long-chain menaquinones (longer than MK-4) include MK-7, MK-8 and MK-9 and are more predominant in fermented foods such as natto. Longer-chain menaquinones (MK-10 to MK-13) are produced by anaerobic bacteria in the colon, but they are not well absorbed at this level and have little physiological impact.[1]
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At present, the following human Gla-containing proteins (Gla proteins) have been characterized to the level of primary structure: the blood coagulation factors II (prothrombin), VII, IX, and X, the anticoagulant proteins C and S, and the factor X-targeting protein Z. The bone Gla protein osteocalcin, the calcification-inhibiting matrix Gla protein (MGP), the cell growth regulating “growth arrest specific gene 6” protein GAS6, periostin (a factor necessary for migration and adhesion of epithelial cells), plus two proline-rich Gla-proteins (PRGPs) and two transmembrane Gla proteins (TMGPs), the functions of which are unknown.[6][7][8]
I am a big fan of natto. I started eating natto a while back after deciding to lower my supplements and replace them with food diversity. I have grown to love the taste. I believe the studies around MK7 are legit - I have been sold on this for a while. I also like to balance 1000iu D with at least 45mcg mk7 (I think this is the optimal ratio based on my research).
I refer to the excellent work of Chris Masterjohn on this subject:
FYI - as a fermented food, I believe natto has benefits that outweigh just K2 content. It’s also the most well tolerated source of soy for most people.
I’m a huge fan of K2. It even makes a difference to how smooth my teeth feel!
The French paradox is most extreme in the south west where they eat a lot of foie gras (massively high in mk4)
I try to target 200mg a day from food and supplements. (Occasional Natto + Jarlsberg cheese + liver pate) Proper Calcium Use: Vitamin K2 as a Promoter of Bone and Cardiovascular Health - PMC suggests the target
