Vitamin K1 vs. K2: What's the Difference?


Vitamin K is a group of fat-soluble vitamins that have a common chemical structure and are stored in the body’s fatty tissue and liver. The two types of vitamin K that are most commonly found in our diets are vitamin K1 (also called phylloquinone or phytonadione) and vitamin K2 (also called menaquinones). 

Because vitamin K1 and vitamin K2 absorb in the body differently and transport to body tissues differently, they may have different effects on your health.

New Edith Cowan University (ECU) research has found that people who eat a diet rich in vitamin K have up to a 34 percent lower risk of atherosclerosis-related cardiovascular disease (conditions affecting the heart or blood vessels).

Researchers examined data from more than 50,000 people taking part in the Danish Diet, Cancer, and Health study over a 23-year period. They investigated whether people who ate more foods containing vitamin K had a lower risk of cardiovascular disease related to atherosclerosis (plaque build-up in the arteries).

There are two types of vitamin K found in foods we eat: vitamin K1 comes primarily from green leafy vegetables and vegetable oils while vitamin K2 is found in meat, eggs, and fermented foods such as cheese.

The study found that people with the highest intakes of vitamin K1 were 21 percent less likely to be hospitalized with cardiovascular disease related to atherosclerosis.

Vitamin K1

  • Found in foods such as green leafy vegetables and vegetable oils.
  • Considered the plant form of vitamin K. However, it is also produced commercially to treat conditions related to excessive bleeding.
  • Essential to the circulatory system. Without it, the liver cannot produce the molecules that ensure coagulation of the blood.
  • Serious deficiency of vitamin K1 poses a risk of hemorrhage.
  • Average recommended values for vitamin K1 intake are 0.08 milligrams for women and 0.12 milligrams for men.

Vitamin K2

  • Made by the bacteria in the gut, which can convert vitamin K1 to vitamin K2.
  • Found in highly fermented foods such as sauerkraut, natto (a Japanese food made of fermented soybeans), cheese, liver, yogurt and dietary supplements. 
  • Supplements the vitamin K1 the body obtains through diet.
  • Like vitamin K1, acts as a protein activator and assists in blood coagulation.
  • More often recognized for its essential role in maintaining arterial flexibility.
  • Activates a protein called matrix Gla-protein (MGP), which contributes to the elimination of calcium in the arteries and thus delays the onset of high blood pressure. 
  • Has a role in calcium metabolism and helps to protect bone density. Without vitamin K2, calcium would not be absorbed by the protein osteocalcin for subsequent binding to and strengthening of the bone matrix.
  • Exact recommended values for vitamin K2 unclear. Currently, it is assumed that about 180-200 micrograms is a sufficient daily dose.

What is vitamin K3?

Vitamin K3 (menadione) is a synthetic version of vitamin K made in the lab. Unfortunately, research has shown that artificial vitamin K3 interferes with one of the body’s naturally occurring antioxidants, glutathione, which can increase oxidative damage to cells. Vitamin K3 may cause liver toxicity, jaundice and anemia from ruptured blood cells. This form of vitamin K is therefore not sold as a dietary supplement.

Vitamin K types, functions, and sources.

Type of vitamin K Function in the human body Sources of vitamin
Vitamin K1 (i) Participates in blood clotting. Serves as a cofactor for carboxylation of protein bound glutamate residues by converting them to carboxy glutamate (GLa). GLa containing proteins are found in Factors II, VII, IX, and X (i) Green leafy vegetables and some plant oils

Vitamin K2, menaquinone-4 (MK-4) (i) Osteocalcin (synthesized in bone)
(ii) Matrix GLa protein (synthesized in cartilage and in blood vessel walls)
It is involved in calcium transport, preventing calcium deposition in the lining of blood vessel walls, and helps improve bone density 
(iii) Short chain form with shorter half-life
(i) Butter, eggs yolks, lard, and animal based foods
(ii) Synthesis by bacteria in the intestinal tract (however, synthesized MK-4 is bound to the membranes of bacteria in the gut and very little is absorbed in humans) 
(iii) Over-the-counter (OTC) supplements

Vitamin K2, menaquinone-7 (MK-7) (i) As for MK-4
(ii) Long chain form with longer half-life
(i) Fermented foods, some cheese
(ii) Extracted from Nattō (fermented soy) as an OTC supplement

Vitamin K3, menadione (i) Has been banned by the FDA in the USA because of potential toxicity
(hemolytic anemia)
(ii) Is presently being studied as a potential prostate/hepatocellular cancer therapy and potential treatment for skin toxicities secondary to kinase inhibitor therapy 
(i) ⁡Synthetic analogue of vitamin K considered a provitamin


What are signs and symptoms of Vitamin K deficiency?

Signs and symptoms of vitamin K deficiency may include:

  • Adults
    • Excessive bleeding from a cut, wound injection or puncture
    • Easy bruising
    • Heavy menstrual bleeding
  • Children and infants
    • Bruising, especially around the head or face
    • Bleeding episodes, such as bleeding from the umbilical cord, around the belly button, nose and mouth, penis (if circumcised) and at vaccination sites
    • Paleness, which may be noticeable in the gums of darker-skinned infants
    • Yellowing of the skin and eyes that is occurring for three or more weeks after birth. 
    • Stool that is bloody, dark or sticky like tar
    • Blood in urine
    • Vomit
    • Irritability

Vitamin K deficiency in adults is rare but common in premature newborns. Newborns are often given a single dose of vitamin K to prevent vitamin K deficiency bleeding (VKDB), which is a rare condition that occurs when the blood can’t clot.

What are good sources of vitamin K?

Most people get enough vitamin K through their diet and supplements. The best sources of vitamin K-1 are dark green leafy vegetables, such as spinach, parsley, broccoli, kale, cabbage, Brussels sprouts and salad greens. Other good sources include green beans, avocados, kiwis and vegetable oils. 

In unique circumstances, your doctor may prescribe vitamin K supplements to help the blood clot or to help increase bone strength. 

Interactions. Many drugs can interfere with the effects of vitamin K. They include antacids, blood thinners, antibiotics, aspirin and drugs for cancer, high cholesterol, and other conditions.

Risks. You should not use vitamin K supplements before consulting with your healthcare provider.


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25.Vitamin K Intake and Atherosclerotic Cardiovascular Disease in the Danish Diet Cancer and Health Study” by Jamie W. Bellinge, Frederik Dalgaard, Kevin Murray, Emma Connolly, Lauren C. Blekkenhorst, Catherine P. Bondonno, Joshua R. Lewis, Marc Sim, Kevin D. Croft, Gunnar Gislason, Christian Torp‐Pedersen, Anne Tjønneland, Kim Overvad, Jonathan M. Hodgson, Carl Schultz and Nicola P. Bondonno, 7 August 2021, Journal of the American Heart AssociationDOI: 10.1161/JAHA.120.020551

This informational is for educational purposes only. Always consult a physician for examination, testing and treatment recommendations. No part of this article  should be used for self-diagnosis, treatment or any other medical decision. The statements made regarding products have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease and are not intended to replace any medical treatment of protocol.  Before taking a new product or beginning any practice relating to health, diet or exercise, it is highly recommended that you consult your licensed healthcare professional.  



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