Vitamin K2 Calcium Relationship

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Vitamin K2 is often described as a “traffic director” for calcium. Calcium is essential, but where it ends up matters A LOT. You want it deposited in your bones and teeth, and not in your arteries, kidneys, joints, or other soft tissues.

The main role of vitamin K2 is activating specific proteins that are manufactured by the body but remain inactive until K2 interacts with them.

The basic mechanism

Vitamin K2 serves as a cofactor for an enzyme called gamma-glutamyl carboxylase.

This enzyme adds carbon dioxide (a process called gamma-carboxylation) to certain glutamate amino acids on vitamin K-dependent proteins.

The resulting chemical change lets these proteins bind calcium very strongly.

Without K2:

  • The proteins are made.
  • But they remain inactive.
  • They can’t effectively bind or transport calcium.

With sufficient K2:

  • The proteins become active.
  • They direct calcium where it belongs.

The two major proteins K2 activates

1. Osteocalcin calcium = into bone

Osteocalcin is produced by osteoblasts (bone-building cells).

Vitamin D stimulates production of osteocalcin.

Vitamin K2 activates it.

Activated osteocalcin binds calcium and incorporates it into the hydroxyapatite crystals that make bones hard.

Without enough K2:

  • Osteocalcin stays undercarboxylated (inactive).
  • Calcium is not incorporated into bone as efficiently.
  • Bone mineral density may suffer over time.

2. Matrix Gla Protein (MGP) — keeps calcium out of arteries

K2’s most intriguing role.

Matrix Gla Protein is made by:

  • blood vessel walls
  • cartilage
  • kidneys
  • lungs
  • other soft tissues

When activated by K2, MGP:

  • binds free calcium
  • inhibits calcium crystal formation
  • prevents calcification of arteries and soft tissues

Inactive MGP is not very good at doing this.

Researchers often measure dephosphorylated-uncarboxylated MGP (dp-ucMGP) as a marker of poor vitamin K status. Higher levels mean more inactive MGP and are associated with more tendency toward vascular calcification.

Vitamin D and K2 work together

Relationship is important.

Vitamin D:

  • increases intestinal calcium absorption
  • increases osteocalcin production
  • Raises MGP production

Vitamin K2:

  • activates osteocalcin
  • activates MGP

Here’s a simplified flow:

Vitamin D

↓

More calcium absorbed

↓

More osteocalcin and MGP produced

↓

Vitamin K2 activates them

↓

Calcium goes to bone instead of soft tissue

Why K2 is different from K1

Vitamin K1 (phylloquinone):

  • abundant in leafy greens
  • primarily supports blood clotting in the liver

Vitamin K2 (menaquinones):

  • produced by bacteria
  • found in fermented foods, grass-fed meat, organs, butter, eggs, aged cheeses.
  • more readily reaches tissues outside the liver, including bone and blood vessels

Because K2 circulates longer than K1, it’s better suited for activating proteins in bone and vascular tissue.

The vitamin K cycle

K2 is recycled.

After helping activate a protein, vitamin K is converted to an epoxide form.

The enzyme vitamin K epoxide reductase (VKOR) converts it into its active form.

So one vitamin K molecule can be active in many cycles.

This recycling explains why relatively small amounts can have significant biological effects.

What happens if K2 is lacking?

If K2 intake is low:

  • more inactive osteocalcin
  • more inactive MGP
  • poorer calcium utilization
  • greater tendency for calcium deposition in tissues other than bone
  • potentially less efficient bone mineralization

This doesn’t necessarily mean calcium leaves bones quickly or that arteries rapidly calcify; those processes are influenced by many factors, including age, kidney function, vitamin D status, diet, exercise, genetics, smoking, diabetes, and blood pressure.

MK-4 vs. MK-7

There are multiple forms of vitamin K2.

MK-4

  • Short half-life (hours)
  • Found in meat, eggs, butter, and some cheeses
  • Rapidly taken up by tissues
  • Often requires multiple doses daily in studies using higher amounts
  • ****I follow the work of Dr. Jack Kruse. He seems to favor this version due to MK-4 having unique tissue distribution and biological activity****

MK-7

  • Long half-life (roughly 2–3 days) – THIS IS THE VARIETY I’M TRYING
  • Found in fermented foods, grass-fed animal parts, milk, and eggs, aged cheeses, raw milk.
  • Maintains steadier blood levels
  • Taken once daily as a supplement

Both activate the same vitamin K-dependent proteins; they mainly differ in how long they remain in circulation.

A simplified summary

Without K2, calcium can still be absorbed, but the body’s calcium-guiding proteins are not fully activated, making calcium handling less efficient.

One important caution: if someone takes the anticoagulant warfarin (Coumadin), they should not start or significantly change vitamin K intake—including K2 supplements—without medical guidance, because warfarin works by interfering with the vitamin K cycle.

Who’s likely to have low K2 intake?

People may have lower K2 intake if:

  • Eat little or no fermented foods.
  • Avoid dairy, eggs, and meat.
  • Have conditions that impair fat absorption (such as certain intestinal, pancreatic, or liver diseases).
  • Have taken long courses of broad-spectrum antibiotics, which affect gut bacteria

For most healthy people, vitamin K2 is considered very safe, and there are no known major drawbacks when taken at typical dietary or supplement doses. However, there are some important considerations.

1. Interaction with blood thinners is the biggest concern

The issue is with vitamin K–antagonist anticoagulants, especially:

  • Warfarin (Coumadin)

Warfarin works by blocking the vitamin K recycling cycle. Taking additional K2 can reduce warfarin’s effectiveness and alter INR (blood clotting measurements).

It doesn’t mean vitamin K is dangerous—it means the medication is designed around controlling vitamin K activity.

People on warfarin should not suddenly add K2 or dramatically change intake without talking to the doctor who placed you on the drug.

2. It may not be appropriate with certain medical situations

Extra caution is reasonable if someone has:

  • History of blood clots and/or is on anticoagulation treatments
  • Kidney disease
  • Certain clotting disorders
  • Having a surgery soon.

3. “Too much calcium” concern

A common question is:

If K2 helps put calcium into bones, could it cause too much calcium in the body?

In healthy people, this is unlikely.

K2 doesn’t add calcium—it just works to regulate where calcium is used by activating proteins involved in dealing with calcium.

The issue is usually taking high-dose calcium supplements without considering vitamin D, K2, magnesium, diet, and overall metabolism.

A food-first approach

For someone not taking warfarin or similar medication, a reasonable approach is:

  • Eat K2-rich foods when possible:
    • aged cheeses
    • eggs from free-range (true) chickens….eggs with yolks that have a vibrant, deep orange color.
    • true fermented foods
    • High quality animal parts/products (think grass-fed)

NOTE: K2 is fat-soluble, so taking it with a meal including fat generally improves absorption.

Jack Kruse connects K2 to insulin sensitivity and hormones

Kruse highlights research involving carboxylated osteocalcin, suggesting that activated osteocalcin acts like a hormone affecting:

  • insulin sensitivity
  • glucose metabolism
  • possibly sex hormone pathways

He discusses K2 as potentially supporting metabolic health through osteocalcin activation.

Kruse’s “evolutionary” argument

Kruse’s work notes that humans evolved with:

  • sunlight exposure
  • eating seafood
  • eating fermented foods
  • eating animal fats
  • & seasonal foods

He argues that modern environments create mismatches, including lower K2 availability.

CONCLUSION

After reading Dr. Kruse’s book Epi-paleo RX: The Prescription for Disease Reversal & Optimal Health (which I highly recommend) – I’ve decided to try adding a K2 supplement to my daily intake because I don’t have consistent access to high-quality food sources. NOTE: One of the things Kruse says you may notice is less plaque buildup on teeth…..so this is something I intend to monitor. Currently, I’ve had issues with plaque forming on my lower front teeth.

Hey….just want to let you know that some of the links are to Amazon. I participate in their “associates” program. IF you buy anything eligible on Amazon within 24 hours after clicking a link, I may earn a commission — even if it is not the exact product linked to. There’s no extra cost to you. You’ll be helping support my endeavors & I greatly appreciate it!

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