Demystifying Vitamin K: What do all those numbers mean, anyway?

By Jonny Bowden, PhD, CNS aka “The Nutrition Myth Buster”™

For years, Vitamin K was the Rodney Dangerfield of vitamins. You can almost picture it sitting around a table with all the other fat-soluble vitamins (like E, A and D), pulling on it’s tie and saying “I don’t get no respect”.

But that was then and this is now.

Vitamin K is finally getting the attention—and the respect– it so richly deserves.

vitamin pills

Let’s start with the basics. Vitamin K is actually the collective name for a group of structurally related compounds. Vitamin K1 is primarily found in green leafy plants (i.e. lettuce, spinach), while vitamin K2 is primarily synthesized by bacteria in the colon.

To make things even more complicated, vitamin K2 comes in several “flavors”, the most important of which are MK4 and MK7, and huge controversies rage over which form is “better”. (Here’s the Cliff Notes: MK4 in food—mainly from grassfed dairy– is great stuff, but all the MK4 in supplements is synthetic, and not nearly as effective as MK7, which is also available to the body a lot longer than the synthetic MK4.)

Now here’s the kicker: Vitamin K1 and vitamin K2 are so different, that many think they should be considered different vitamins.

So first let’s look at vitamin K1.

One of the most important things vitamin K1 does is assist the body with clotting, meaning it has “anti-hemorrhagic” activity. This is why doctors say you have to avoid green leafy vegetables—the best source of vitamin K1— when you’re on Coumadin. Coumadin thins the blood. It’s given— usually to older people—when the doctor is afraid your blood will clot too easily, producing a stroke. Since vitamin K1 helps make clotting happen, the doctor tells you to limit green leafy vegetables. (We can discuss the “wisdom” of this advice another time.) Interesting trivia—vitamin K got it’s name from koagulation, the German word for clotting.

But vitamin K2 does a lot more than help with clotting. “New evidence…. has confirmed that vitamin K2′s role in the body extends far beyond blood clotting to include protecting us from heart disease, ensuring healthy skin, forming strong bones, promoting brain function, supporting growth and development and helping to prevent cancer – to name a few”, writes Chris Kresser, L.Ac.(1)

Vitamin K2 and your bones

Vitamin K2 is vitally important for strong healthy bones. A bone-related protein called osteocalcin is known to be a sensitive marker of bone formation because it has the capacity to bind minerals like calcium to bone. When osteocalcin is “undercarboxylated”, it’s more or less defective—it doesn’t bind minerals to bones very well. Carboxylation is dependent on vitamin K. Studies have shown that under-carboxylated osteocalcin is highly predictive of hip fracture. Research has also shown that those who already have osteoporosis have a lower level of vitamin K2.

Now here’s where it gets interesting.

Vitamin K2 and your heart

This same vitamin K-dependent “carboxylation” process that makes osteocalcin so effective for bone-building also works on a special protein called MGP (or matrix Gla protein). When MGP is carboxylated, it has heart-protective benefits! Carboxylated MGP actually helps prevent calcification in the arteries. But without enough vitamin K2, MGP isn’t carboxylated, and therefore can’t do its work of protecting your heart from “hardening of the arteries” (calcification). No vitamin K2, no carboxylation.

Do you get enough?

For decades, the conventional wisdom was that everyone got enough vitamin K from their diet, and there was no need to supplement. Is that so? Maybe, maybe not. A recent survey conducted by Sarah Booth of the Vitamin K Laboratory at the Jean Mayer USDA Human Nutrition Research center on Aging at Tufts University in Boston suggests the latter. Only half the females age 13 and over, and less than half the males got the RDA, she notes. “This confirms there are very low intakes nationwide”.(1)

What’s more, antibiotics in our food supply reduce the intestinal bacteria that make vitamin K2!

Remember to take vitamin K with a meal containing some fat, since it is a fat-soluble vitamin. And make sure that your vitamin K supplement contains a healthy dose of vitamin K2, preferably of the MK-7 variety.


By Jonny Bowden, PhD, CNS aka “The Nutrition Myth Buster”™