This blog post examines the role of vitamin K, crucial for blood clotting and vascular health, and provides key information for preventing atherosclerosis and vascular calcification.
Blood plays a vital role in supplying oxygen and nutrients to cells while simultaneously removing waste products generated during cellular metabolism. Blood circulation provides vitality to all tissues in the body, and disruptions in this process can lead to various health issues. If blood vessel walls are damaged and bleeding occurs, blood must rapidly clot at the injury site to prevent blood loss. This process is called ‘hemostasis’ and is an essential defense mechanism for human survival.
Blood clotting occurs when a fibrin network, formed by the aggregation of the fibrin protein, combines with a platelet plug—a mass of aggregated platelets—to create a clot. This clot seals the damaged area, preventing further blood loss and allowing time for the wound to heal. Blood clotting also occurs within blood vessels; a clot formed in a vessel is called a ‘thrombus’. Generally, thrombi are rapidly removed from the vessel to avoid disrupting normal blood flow. However, under certain conditions, excessive thrombus formation can occur, potentially blocking the vessel. This situation carries a risk of blocking blood supply to vital organs, particularly the brain or heart.
When atherosclerosis occurs, causing the arterial walls to thicken due to the buildup of foreign substances, thrombi can easily deposit in that area, reducing blood flow and potentially developing into vascular disease. Atherosclerosis often progresses slowly and is asymptomatic in its early stages, but as the vessels gradually narrow, it can lead to serious health problems. Maintaining the balance between smooth blood circulation and thrombus formation is therefore crucial, and vitamin K plays an important role in this process.
Vitamin K is an essential nutrient that helps blood clot. It was discovered that chicks fed a diet lacking fat were deficient in a fat-soluble substance, causing delayed blood clotting. This substance was named vitamin K. Subsequent research revealed that vitamin K is essential not only for blood clotting but also for various physiological functions.
Blood coagulation occurs through a chain reaction involving various protein factors. First, multiple coagulation factors are activated, leading to the activation of prothrombin, which converts to thrombin. Thrombin then transforms soluble fibrinogen in the blood into insoluble fibrin. In this process, vitamin K is involved in the activation of blood coagulation factors, including prothrombin, when they are synthesized in liver cells. Activation occurs through binding with calcium ions, and these blood proteins must be carboxylated to bind with calcium ions. Carboxylation refers to the conversion of glutamic acid, one of the amino acids composing the protein, into gamma-carboxyglutamic acid. Target proteins that require carboxylation by vitamin K for activation are termed vitamin K-dependent proteins.
Vitamin K is divided into vitamin K1, synthesized in plants, and vitamin K2, synthesized in animal cells or produced by microbial fermentation. Green vegetables and similar foods contain sufficient vitamin K1, so following a typical recommended diet prevents issues with blood clotting. Vitamin K is not only essential for the hemostasis process but is also closely linked to bone health. In fact, research indicates that vitamin K deficiency may increase the risk of osteoporosis.
Another crucial function of vitamin K related to vascular health has been discovered, linked to the calcium paradox. As we age, bone tissue calcium density decreases, making osteoporosis more likely, so calcium supplements are taken to prevent this. However, while calcium supplements raise blood calcium levels, they do not increase bone density. In this case, excess calcium in the blood may not be absorbed into the bones and instead deposit as calcium salts on the walls of blood vessels. This is called vascular calcification, which can cause atherosclerosis and vascular disease.
Vascular calcification is inhibited by a protein called MGP, produced in vascular muscle cells, among others. This protein is vitamin K-dependent. A deficiency in vitamin K prevents the activation of MGP, thereby inducing vascular calcification. Therefore, vitamin K is closely related not only to its role in aiding blood coagulation but also to overall vascular health.
Both vitamin K1 and K2 induce the activation of vitamin K-dependent proteins, but K1 is primarily active in liver cells, while K2 is more active in other cells. Thus, K1 primarily activates blood clotting factors, while K2 mainly activates proteins synthesized in other cells. Consequently, some researchers recommend setting separate recommended intakes for K1 and K2 and increasing consumption of animal-based foods like cheese and butter, as well as fermented foods, which contain K2.
Furthermore, the importance of vitamin K is increasingly emphasized by recent research. Beyond vascular disease and bone health, evidence is growing that vitamin K plays a crucial role in preventing cardiovascular and metabolic diseases. This suggests that vitamin K is not merely a supplementary nutrient but an essential factor for overall human health.
