Vitamin K: Functions, Sources, Deficiency, Symptoms and Health Benefits

Vitamin K is a fat-soluble vitamin that is essential for the production of blood clotting factors. It is also important for bone health, and it helps in the absorption of calcium. It is also called as K1, as it was the first form of vitamin K discovered.

It has been known even before 1940s that there are two forms of Vitamin K:

  • Vitamin K-1, or phylloquinone, comes from plants, especially in dark leafy green vegetables like spinach and kale and is the main dietary source of vitamin K.
  • Vitamin K-2, or menaquinone, is present in small quantities in organ meats and fermented foods. Gut bacteria also produce vitamin K-2.

Vitamin K deficiency is rare in adults because many of the foods we eat contain adequate amounts of K1, and because the body makes K2 on its own. Plus, the body is good at recycling its existing supply of vitamin K. However, certain conditions and some drugs can interfere with vitamin K absorption and creation, making it possible to become deficient.

Vitamin K deficiency can lead to the development of osteoporosis, which causes bones to become fragile and susceptible to fracture. Vitamin K deficiency can also cause people to bleed excessively. The most common symptom of vitamin K deficiency is easy bruising.

The body does not produce vitamin K on its own, so it must be obtained from diet or supplements. Vitamin K can be found in leafy green vegetables such as spinach, broccoli, and lettuce. Other foods that contain vitamin K include eggs and dairy products such as cheese and milk.

Functions of Vitamin K

The body needs both types of vitamin K to produce prothrombin, a protein that plays crucial roles in blood clotting, bone metabolism, and heart health. Vitamin K also helps facilitate energy production in the mitochondria of cells.

Vitamin K-1 is primarily involved in blood coagulation. K-2 may have a more diverse range of functions in the body.

Vitamin K has antioxidant properties. It protects cellular membranes from damage due to excess free radicals, in a process known as peroxidation. Blood thinning medication, such as warfarin, can lower the antioxidative potential of vitamin K.

Sources of Vitamin K

Several foods are rich in vitamin K-1, and vitamin K-2 is much less common. Bacteria in the gut can convert some K-1 into K-2. Fermented foods are a good source of vitamin K-2.

Also, because it is fat-soluble, organ meats and high-fat dairy products contain fairly substantial quantities of vitamin K-2. Conversely, lean meats, such as poultry, are not good sources of K-2.

Dietary sources of vitamin K-1 include:

Dietary sources of vitamin K-2 include:

  • Natto a fermented soybeans
  • Sauerkraut
  • Dairy products, especially hard cheeses
  • Liver and other organ meats
  • Beef
  • Pork
  • Egg yolks
  • Chicken
  • Fatty fish, such as salmon

Benefits of Vitamin K

Vitamin K is a nutrient that is essential for blood clotting and bone health. It is also necessary for the production of certain proteins that are important in blood coagulation.

People should take Vitamin K supplements if they have a deficiency or are at risk of developing one.

Some benefits of Vitamin K include:

  • Reduces the risk of bleeding
  • Improves bone health
  • Improves cardiovascular health
  • Cognitive health

Vitamin K deficiency

Vitamin K deficiency is a condition that can occur when the body does not have enough vitamin K. Vitamin K is needed for blood clotting. A lack of vitamin K can lead to excessive bleeding, bruising, nosebleeds, and heavy menstrual bleeding.

Vitamin K deficiency is usually caused by an underlying medical condition or medication use that interferes with the absorption of vitamin K in the gut or prevents it from being converted into a form the body can use. It may also be caused by inadequate dietary intake of vitamin K.

Deficiency Symptoms

The main symptom of vitamin K deficiency is excessive bleeding. Keep in mind that bleeding may happen in areas other than at a cut or wound site. The bleeding may also be apparent if someone:

  • Bruises easily
  • Gets small blood clots underneath their nails
  • Bleeds in mucous membranes that line areas inside the body
  • Produces stool that looks dark black (almost like tar) and contains some blood

In infants, doctors may observe vitamin K deficiency if there is:

  • Bleeding at the penis if the baby has been circumcised
  • Bleeding in the skin, nose, the gastrointestinal tract, or other areas
  • Bleeding from the area where the umbilical cord is removed
  • Sudden bleeding in the brain, which is extremely dangerous and life-threatening


Vitamin K is a fat-soluble vitamin that is needed for the blood to clot. The two major forms of Vitamin K are Vitamin K1, which comes from plants, and Vitamin K2, which comes from animals.

Vitamin K is an essential nutrient that is important for blood clotting. It can be found in leafy green vegetables, like spinach and kale, as well as in other vegetables such as broccoli, cabbage, and cauliflower. Vegetables are not the only source of Vitamin K: it can also be found in soybeans, eggs, and meat.

Vitamin K has a number of functions in the body including helping to form proteins that are necessary for bone health and helping to prevent excessive bleeding by activating a protein called prothrombin. Vitamin K deficiency can lead to increased risk of fractures or hemorrhaging.

The recommended adequate intake for vitamin K depends on age and gender. Women aged 19 years and over should consume 90 micrograms (mcg) a day, and men should have 120 mcg.