Vitamin K1 and Its Most Critical Role

Updated: March 31, 2023

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Lara Pizzorno is the author of “Your Bones: How You Can Prevent Osteoporosis and Have Strong Bones for Life – Naturally” and a member of the American Medical Writers Association with 29 years of experience specializing in bone health.

Recently we asked Lara if she would help us provide a series of short, ongoing videos to help you (our customers and readers) stay up to date on the latest facts and science related to bone health.

In this latest video, Lara discusses the most important job that vitamin K1 has in the body. Watch the video below (or read the transcript provided) and let us know what you think in the comments. 🙂

Hello. My name’s Lara Pizzorno. I’m the author of “Your Bones” and I’m here to share some information with you that I hope will help you to have healthier bones. In these series of videos we’re talking about Vitamin K, and in this particular video we’ll discuss how Vitamin K1 works and what happens when your Vitamin K1 is too low.

So the scientific name for Vitamin K1 is phylloquinone, and it’s called this because it’s made by plants. Now phyllo is Greek for leaf and the quinone part of phylloquinone refers to the chemical structure of this compound. Phylloquinone is found in the greatest amounts in green leafy plants where it plays a major role in the plant’s photosynthesis, which is the way that plants make energy for themselves. In our bodies phlloquinone plays, at least, two essential roles. It’s required for our blood to clot and it is also a potent anti-inflammatory nutrient.

As I’ve mentioned before, anything that promotes chronic low-grade inflammation increases both the activation and activity of the specialized cells that break down bone, the osteoclast, and therefore promotes bone loss.

Helping our blood to clot is Vitamin K1’s most critical role because without enough K1 we would simply bleed to death from even a tiny paper cut or a shaving cut.

For this reason, any K1 that we get from the foods we eat, mainly the plants, leafy greens that we eat or if we take some in a supplement, goes immediately to our liver where it is used to activate the clotting factors just in case we need them. Vitamin K1 does this by being the co-factor in an enzyme called gamma-glutamyl carboxylase and without Vitamin K1 this enzyme doesn’t work. And we have to have it work because when K1 serves as its co-factor, it activates some of the Gla or G-L-A proteins specifically the Gla proteins that are involved in the blood clotting cascade.

And these involve Factors II, VII, IX, and X and the proteins C and S. When K2 serves as the co-factor for gamma-glutamyl carboxylase, it activates or carboxylates other Gla proteins, two of which determine where calcium that we absorb from the food or supplements we consume, particularly when we take calcium along with Vitamin D, gets sent. And these proteins are called osteocalcin which brings calcium into bone and matrix-Gla protein which prevents calcium from depositing in soft tissues, like our arteries.

We’ll talk more about K2 later, but for now I’m bringing this up because I sometimes hear from people who are concerned that taking Vitamin K will make their blood more likely to clot, and this is not a concern for two reasons.
  1. First, once the proteins that are involved in blood clotting are activated by Vitamin K1, no matter how much more Vitamin K1 is around no more blood clotting proteins are going to be available to get activated. If we have extra K1, we do not make more blood clotting proteins in response to it.
  2. Secondly, K2, the other form of Vitamin K, doesn’t activate the blood clotting proteins at all. It activates very different proteins, the ones that regulate where calcium goes in our bodies. If we eat lots of the leafy green plant foods that are the best source of Vitamin K1, then any extra K1 that we don’t need, once our blood clotting proteins have been activated and so we’re protected against bleeding out and dying, those extra K1s will be used to lower the production of pro-inflammatory signaling agents that our bodies produce.

Vitamin K1 greatly lessens the body’s production of a wide range of these pro-inflammatory signaling compounds including compounds like interleukin 6, tumor necrosis factor, and C-reactive protein and by doing so Vitamin K1 lowers overall inflammation. This is really important for bone health because when inflammation increases, particularly when it’s chronic, this signals the body to also increase the production and activation of the specialized cells that break down bone, the osteoclast.

Before menopause, estrogen will also put a damper on women’s production of these pro-inflammatory compounds. But as estrogen levels drop with menopause, the body’s production of pro-inflammatory signaling molecules gets higher so Vitamin K1 is especially important for us post-menopausal women since it helps keep inflammation and therefore the production of osteoclast under control. If we really eat a lot of K1 rich leafy greens, then not only will we have enough K1 to produce clotting factors and to lessen inflammation in our bodies but a little bit can still be left over and in that case the extra K1 gets sent to our intestines where health promoting bacteria will use it, will convert it into a form of K2 called MK4.

We’ll talk more about the MK4 versus MK7 forms of K2 later, but I just wanted to mention this now because you need to know that mainly the K1 that we consume is going to be used to produce clotting factors and to lessen inflammation. Very little of it will be left to go to the intestines and if you have healthy bacteria there to convert it into the MK4 form of K2. In terms of our bones, K1’s anti-inflammatory actions are the main ways that this nutrient protects us against osteoporosis, but K1’s anti-inflammatory actions do even more for us. They’ve also been shown to protect us against Type II diabetes and even obesity, and both Type II diabetes and obesity increase bone loss and increase our risk for osteoporosis.

I’ll tell you about some of the studies showing how important Vitamin K1 is for us in protecting us against Type II diabetes and obesity in our next video, and I hope this one has been helpful for you. Thanks, I’ll see you next time.


Shea MK, Dallal GE, Dawson-Hughes B, et al. Vitamin K, circulating cytokines, and bone mineral density in older men and women. Am J Clin Nutr. 2008 Aug;88(2):356-63. PMID: 18689371

Mundy GR. Osteoporosis and inflammation. Nutr Rev. 2007 Dec;65(12 Pt 2):S147-51. PMID: 18240539

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This article features advice from our industry experts to give you the best possible info through cutting-edge research.

Lara Pizzorno
MDiv, MA, LMT - Best-selling author of Healthy Bones Healthy You! and Your Bones; Editor of Longevity Medicine Review, and Senior Medical Editor for Integrative Medicine Advisors.,
Dr. Liz Lipski
PhD, CNS, FACN, IFMP, BCHN, LDN - Professor and Director of Academic Development, Nutrition programs in Clinical Nutrition at Maryland University of Integrative Health.,
Dr. Loren Fishman
MD, B.Phil.,(oxon.) - Medical Director of Manhattan Physical Medicine & Rehabilitation and Founder of the Yoga Injury Prevention Website.,
Prof. Didier Hans
PHD, MBA - Head of Research & Development Center of Bone Diseases, Lausanne University Hospital CHUV, Switzerland,