I’m not the world’s greatest nutrition expert, but thanks to some research I had to do a couple years ago, I know a bit about Vitamin K. And there’s a lot of confusing information out there about Vitamin K, so I wanted to post this topic to hopefully educate and influence what goes into Soylent (Or maybe it already has the correct variant! I can’t tell from the ingredients list). I haven’t included research links at this time because they are easily found at Wikipedia or via Google – this isn’t supposed to be an exhaustive reference.
Broadly speaking, there are three variants of Vitamin K: K1, K2-4, and K2-7. (K2-8 and K2-9 also exist but aren’t readily for sale. You can ignore these) The numbers after the “–” in K2 indicate the number of carbon atoms in the chain following the quinone ring.
K1 is the form synthesized by plants for their own use. It’s concentrated in the green bits, so you’ll find it in blades of grass and the like. Animals (like homo sapiens) cannot use K1 directly. It must be converted into K2 before it can be used.
K2-4 is the variety synthesized by humans (and all mammals, birds and fish that I’m aware of) from K1. Because it is possible for humans to convert K1 into K2-4, however inefficiently, you won’t suffer acute Vitamin K deficiency given a large enough supply of K1. However this is not associated with optimal health. Although the modern world has avoided acute K2 deficiency thanks to the K1 in vegetables, nearly everyone is deficient for purposes of optimal bone and dental health. This a primary reason behind dental cavities, the need for braces as teenagers to straighten our teeth, and bones that break easily and heal slowly.
A generous source of K2-4 is necessary for optimal bone and dental health, much higher than the FDA’s current RDA (which is based on avoiding acute distress only). Primitive peoples who have no dental cavities (at all) in their archaeological record seem to be universally associated with a rich animal-based source of K2-4, usually eggs (fish or poultry), liver, or dairy (butter). And thankfully, the liver clears excess K2-4 easily and there is no known toxic dose.
K2-7+ variants are produced by bacterial action. You can find it in natto and cheese. Some research indicates that this variant can produce similar benefits as K2-4, but no creature that I’m aware of synthesizes K2-7+ for its own use or for consumption by its young. Marketing materials from the vitamin companies that sell K2-7 claim it remains in the blood stream longer than K2-4 (true) and is therefore more “bioavailable” (B.S.) The way I see it, K2-7 isn’t getting absorbed by the tissues at the same rate as K2-4 because the tissues soak up the good stuff as fast as they can and only use K2-7 reluctantly. I would avoid this variant if K2-4 can be made available from suppliers at scale.