Vitamin K exists in two main forms: (1) vitamin K1, or phylloquinone, which is found in leafy green vegetables and is transported to the liver to support the production of coagulation factors, and (2) vitamin K2, or menaquinone, which is found in certain animal products and fermented dairy, and is also produced by gut microbiota. Vitamin K2 is transported to tissues, such as the bone and vascular wall, where it plays a key role in regulating the activity of matrix Gla protein and osteocalcin (bone Gla) protein through carboxylation.
Vitamin K2, or menaquinone, has several forms depending on the length of its side chain, which is delineated with MKn, where n can be from 1 to 14. MK-4 represents 90% of the total vitamin K stored in the human body. Animal studies have shown that long-chain forms of K2 convert into MK-4 in all tissues, except the liver.
Vitamin K2 has been shown to have a role in supporting cardiovascular health. The dietary intake of menaquinone (or vitamin K2) was assessed in the Rotterdam Study in which 4,807 patients with no history of myocardial infarction were followed for 7 to 10 years. Certain cardiovascular disease markers were documented, such as coronary heart disease and aortic atherosclerosis, along with the intake of both phylloquinone (K1) and menaquinone. The study findings indicated that dietary menaquinone intake improved the risk of coronary heart disease mortality and aortic calcification, yet outcomes were not dependent on phylloquinone intake.
Current research suggests that the combined supplementation of both vitamins D and K can be more effective than either vitamin alone for both bone health and cardiovascular health. In animal studies, vitamin K was given to prevent osteoporosis in rats, but prevention of bone loss only occurred in those fed with a diet containing vitamin D or those that received vitamin D supplementation. Due to the evidence of the synergistic relationship between vitamin D and vitamin K, some dermatologists suggest that supplementing with vitamin K2 can be supportive to sun-protected patients.
Vitamin K is currently being studied as a potential theoretical treatment for mutation-related mitochondrial dysfunction related to Parkinson’s disease due to its electron-donor status and potential to assist in the electron transport chain.
Further research has been conducted regarding the potential role of vitamin K in supporting the treatment of autoimmune diseases. A study on the effect of vitamin K2 on mitogen-activated peripheral blood mononuclear cells in patients with rheumatoid arthritis showed a significant relationship between IC50 values of vitamin K2 and laboratory markers such as C-reactive protein and rheumatoid factor.
Vitamin K2 has been shown to be supportive in cardiovascular health and bone health. Current research suggests it may have a role in supporting a healthier autoimmune response in addition to mitochondrial function.
By Colleen Ambrose, ND, MAT