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Vitamin K

Phytonadione, menaquinone-4, & menaquinone-7

Vitamin K refers to a group of vitamins that play an important role in blood clotting and bone metabolism in the body.

Three forms of vitamin K

Sourced from China and India

Disclaimer: The information provided on this page is not a substitute for professional medical advice, diagnosis, or treatment. If you have any questions or concerns about your health, please talk to a healthcare provider.

Studies show that supplementation with vitamin K2 can have beneficial effects on bone mineral density and that supplementation with vitamin K1 and vitamin K2 is associated with a reduction in fractures.

Vitamin K may interact with several medications. If you are taking the medication warfarin (brand name Coumadin), do not take supplements containing vitamin K without first talking to your healthcare provider.


Vitamin K is a group of fat-soluble vitamins that are involved in several of the body’s processes. The other fat-soluble vitamins are vitamin A, vitamin D, and vitamin E. Vitamin K1 is the main form of vitamin K that humans eat and is called phylloquinone when it is made naturally and phytonadione when it is made synthetically. Vitamin K2 is subdivided into several menaquinones labeled menaquinone 4 (MK-4) through menaquinone-13 (MK-13). Vitamin K3 is a synthetic form of vitamin K called menadione. It was found to be potentially toxic and is no longer used in supplements.

Vitamin K comes from food. Vitamin K1 is mostly found in vegetables, particularly leafy green vegetables like spinach, broccoli, and lettuce. Vitamin K2 is mostly found in animal-based foods like meat, dairy, and eggs. However, bacteria also make vitamin K2, so it can be found in fermented foods as well (1).

Vitamin K performs very important functions in the body. One of the functions of vitamin K is the production of proteins involved in blood clotting. Vitamin K is required for the synthesis of pro-clotting proteins known as factors II, VII, IX, and X. Vitamin K is also required for the synthesis of anti-clotting proteins known as proteins C, S, and Z. Outside of the blood, vitamin K is important for bone metabolism.

Vitamin K may also have the following health benefits, which is why it was chosen to be an ingredient in the Ro supplements:

Heart Health

Vascular calcification is a condition that refers to the deposition of calcium on the inside of blood vessels. This causes blood vessels to become stiff, which is a risk factor for coronary heart disease. While the exact role of vitamin K on the development of heart disease is unclear, multiple studies have shown that vitamin K supplementation may lead to decreased coronary artery calcification (1). Studies have also shown that increasing the intake of vitamin K is associated with a reduction in coronary events (2). However, these benefits have only been seen with vitamin K2 and it is unclear whether vitamin K2 is the cause. Vitamin K1 is not associated with improvement in cardiovascular function.

One important note for those with heart disease: Vitamin K directly interacts with warfarin (brand name Coumadin). This is a medication that is commonly prescribed for people with blood clots or atrial fibrillation (also called A-fib). If you are taking warfarin, do not take supplements containing vitamin K without first talking to your healthcare provider.

The Adequate Intake (AI) level of vitamin K is 120 mcg per day for men over the age of 18 and 90 mcg per day for women over the age of 18. This value does not distinguish between vitamin K1, vitamin K2 (MK-4), vitamin K2 (MK-7), or any other form of vitamin K. The AI represents the daily amount of a vitamin that is assumed to ensure nutritional adequacy (1).

Vitamin K status is typically not checked unless an individual has a bleeding disorder. It is unknown exactly how much vitamin K should be in the body. However, most American diets are considered to have adequate amounts of vitamin K. Things that may predispose an individual to be vitamin K deficient include taking certain medications or having a disorder that interferes with fat absorption.

Since vitamin K is involved in both blood clotting and bone metabolism, the symptoms of a vitamin K deficiency include (1):

  • Bleeding

  • Easy bruising

  • Blood in the urine

  • Reduced bone mineralization, which may lead to osteoporosis