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

Available in:

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.

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.

What is vitamin K?

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.

Where does vitamin K come from?

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 (4).

What are the health benefits of vitamin K?

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 Roman Dailies:

Bone Health

Vitamin K is required for the synthesis of a protein called osteocalcin, which is present in bone and is involved in bone formation and reabsorption back into the body. Vitamin K has been studied numerous times to determine if it is effective for the treatment of osteoporosis, particularly in postmenopausal women. One study showed that 6–12 months of supplementation with 1,500 mcg per day of MK-4 led to improved bone quality in postmenopausal Japanese women (3). Another study showed that three years of supplementation with 180 mcg per day of MK-7 had numerous effects in postmenopausal women, including improving age-related decline in bone mineral density, improving bone strength, and decreasing the loss of height in portions of the spine (2). A review of eight studies also found that supplementation with a synthetic version of MK-4 had positive effects on the number of fractures in postmenopausal women with osteoporosis (1).

Regarding vitamin K1, one study found that supplementation with 500 mcg per day for three years did not improve bone mineral density but the treatment group did have 50% fewer fractures. While there are no guidelines regarding the use of vitamin K for osteoporosis in the United States and the FDA has not evaluated or approved vitamin K for the treatment or prevention of osteoporosis, vitamin K2 is used as part of treatment in Japan (5).

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 (4). Studies have also shown that increasing the intake of vitamin K is associated with a reduction in coronary events (5). 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.

How much vitamin K is recommended?

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 (4).

What are the symptoms of having too little vitamin K?

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 (4):

  • Bleeding
  • Easy bruising
  • Blood in the urine
  • Reduced bone mineralization, which may lead to osteoporosis

What are the symptoms of having too much vitamin K?

Studies have not revealed a level at which vitamin K becomes toxic or harmful to the body.

Some people may take a medication called warfarin (brand name Coumadin) that opposes the actions of vitamin K. These individuals need to consume a consistent amount of vitamin K each day. Having too much vitamin K while taking warfarin could cause the medication to be less effective, leading to blood clots and possibly death.

What to look for in a good vitamin K supplement:

Vitamin K is available in a wide variety of supplements, typically as phylloquinone, phytonadione, MK-4, or MK-7. There is no good data regarding how well the body absorbs one type of vitamin K versus another.

How does Roman offer vitamin K?

Roman offers three different forms of vitamin K:

  1. Vitamin K1: Roman obtains vitamin K1 from non-GMO sources in China and India. It is available synthetically as phytonadione on dicalcium phosphate.
  2. Vitamin K2 (MK-4): Roman obtains vitamin K2 (MK-4) from a non-GMO source in China. It is available synthetically as menaquinone-4 on dicalcium phosphate.
  3. Vitamin K2 (MK-7): Roman obtains vitamin K2 (MK-7) from a non-GMO source in China. It is available synthetically as menaquinone-7 on dicalcium phosphate.

Roman offers vitamin K in the following supplements:

Bone Health

Roman’s Bone Health supplement contains all three forms of vitamin K. The total daily dose of vitamin K1 is 100 mcg. The total daily dose of vitamin K2 (MK-4) is 1,500 mcg. The total daily dose of vitamin K2 (MK-7) is 200 mcg. These doses are divided evenly between three tablets. Roman’s Bone Health supplement also contains seven other main ingredients. The supplement is intended to be taken with water.

Other ingredients in the tablets include ascorbic acid, calcium citrate, D-alpha tocopheryl succinate, magnesium citrate, silicon dioxide, boron citrate, cholecalciferol, microcrystalline cellulose, stearic acid, dicalcium phosphate, croscarmellose sodium, magnesium stearate, and pharmaceutical glaze (shellac, povidone).

Heart Health

Vitamin K2 (MK-7) is one of seven main ingredients in Roman’s Heart Health supplement. The supplement consists of four tablets and two fish oil softgels that should be taken with water. Each individual tablet contains 50 mcg of vitamin K2 (MK-7), for a total daily dose of 200 mcg.

Other ingredients in the tablets include spirulina whole plant powder, deodorized garlic bulb powder, magnesium citrate, Coenzyme Q10, cholecalciferol, microcrystalline cellulose, dicalcium phosphate, stearic acid, croscarmellose sodium, magnesium stearate, silicon dioxide, and pharmaceutical glaze (shellac, povidone). Ingredients in the fish oil softgels include marine lipid concentrate, gelatin, glycerin, purified water, and mixed tocopherols. The softgels contain fish and should not be consumed by anybody with a fish allergy.

Does vitamin K interact with any other drugs or medical conditions?

Vitamin K interacts with several other medications. If you are taking any of the following medications, it is important you talk to your healthcare provider before beginning vitamin K supplementation (please note that this list may not be exhaustive and other medications may also interact with vitamin K):

  1. Warfarin (brand name Coumadin): Warfarin works by decreasing the activity of vitamin K in the body. It is very important to consume a consistent amount of vitamin K while taking warfarin. If you are on warfarin or any medication that works in a similar way (including phenprocoumon, acenocoumarol, and tioclomarol), do not take Roman’s Bone Health supplement or Roman’s Heart Health supplement without first talking to your healthcare provider.
  2. Antibiotics: Certain antibiotics, such as cephalosporins, may decrease the amount of vitamin K in the body.
  3. Bile acid sequestrants: This group of medications may decrease the absorption of vitamin K in the digestive system.
  4. Orlistat: This medication may decrease the absorption of vitamin K in the digestive system.


  1. Iwamoto J. Vitamin K2 Therapy for Postmenopausal Osteoporosis. Nutrients. 2014;6(5):1971-1980. doi:10.3390/nu6051971.
  2. Knapen MHJ, Drummen NE, Smit E, Vermeer C, Theuwissen E. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International. 2013;24(9):2499-2507. doi:10.1007/s00198-013-2325-6.
  3. Koitaya N, Sekiguchi M, Tousen Y, et al. Low-dose vitamin K2 (MK-4) supplementation for 12 months improves bone metabolism and prevents forearm bone loss in postmenopausal Japanese women. Journal of Bone and Mineral Metabolism. 2013;32(2):142-150. doi:10.1007/s00774-013-0472-7.
  4. Office of Dietary Supplements – Vitamin K. NIH Office of Dietary Supplements. Accessed November 18, 2019.
  5. Schwalfenberg GK. Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health. Journal of Nutrition and Metabolism. 2017;2017:1-6. doi:10.1155/2017/6254836.