Vitamin K isn’t a well-known vitamin, yet it plays a crucial role in the body. It is involved in the coagulation (or clotting) of blood which is needed to patch vascular injuries and prevent major bleeding. Its name comes from the German word “koagulation” which simply starts with the letter K.
Vitamin K is routinely administered at birth in the United States, to prevent vitamin K deficiency bleeding (VKDB) in infants up to 6 months old (1). While coagulation is what this vitamin is most known for it also plays an active role in bone and vascular health.
Defining Vitamin K
Vitamin K is the name used to refer to a group of molecules with a similar chemical structure. This includes vitamin K-1 (phylloquinone) and vitamin k-2 (menaquinones). K-1 is found in leafy vegetables and many other plant products, while K-2 can be found in fermented foods and animal products.
We get the majority of our vitamin K-1 by consuming plant products. K-2, however, can be synthesized by microbes in the gut- a reason why probiotics promote K-2 and antibiotics oppose it.
Vitamin K is fat-soluble and can be stored in the liver and fat tissue- but only in small amounts. For this reason, it is necessary to maintain healthy levels of this vitamin through diet.
Roles in the Body
Blood Coagulation (clotting)- Vitamin K is a cofactor that helps activate many proteins involved in the coagulation of blood. This prevents an individual from bleeding out internally and helps repair damaged blood vessels in a process known as hemostasis.
Vitamin K antagonists, like Warfarin, oppose coagulation and are known as anticoagulants (or blood thinners). Individuals that are taking blood thinners should be careful of what they eat since vitamin K consumption may interfere with the medication.
Injection at Birth- A vitamin K shot is commonly given at birth to prevent hemorrhages (bleeding) in the newborn. The low vitamin K in the newborn is partly due to limited movement of vitamin K through the placenta and minute amounts in breastmilk. Furthermore, a newborn’s gut microbes aren’t developed enough to produce K-2 on the own.
Bone Health- Vitamin K seems to promote bone density in individuals with osteoarthritis and lower the incidence of bone fractures. This is partly due to vitamin k’s activation (gamma-carboxylation) of the protein osteocalcin, which is involved in the mineralization of bone. Research suggests that it might also work with vitamin D to promote bone density.
Vascular Health- Growing research suggests that vitamin k has a role in protecting blood vessels. It does so by limiting calcium deposition in the vascular lining- a contributing factor to atherosclerosis. Atherosclerosis is the process by which a plaque forms in an artery wall limiting blood flow and contributing to ischemia. It is a major risk factor for cardiovascular disease (CVD).
Vitamin K Deficiency
Deficiency is not very common although it can happen. Low vitamin K can predispose an individual to major bleeding, fractures, and atherosclerotic plaques. Symptoms may include bloody gums, easy bruising, and nosebleeds. An individual with a balanced diet, however, should not worry much about this deficiency.
Should I Supplement?
Unless recommended by a doctor or dietitian, avoid supplementing on vitamin k. There are plenty of food sources that provide this vitamin and its deficiency is already unlikely. Excess vitamin k may interfere with other medications -like blood thinners- which will only complicate things. It best to eat a well-balanced diet and to consult a professional when in doubt.
- “Vitamin K Deficiency Bleeding.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 31 Mar. 2014, www.cdc.gov/ncbddd/vitamink/faqs.html.
- Weber, P. “Vitamin K and Bone Health.” PubMed, NCBI, Dec. 2001, www.ncbi.nlm.nih.gov/pubmed/11684396.