Vitamin K, a fat-soluble vitamin, is absorbed in the presence of bile, pancreatic juices, and is enhanced by dietary fat. Once absorbed, vitamin K is transported by chylomicrons which are microscopic lipid particles that transport fat-soluble components through the lymph. Vitamin K is moderately stable to heat, but unstable to light, acid, and alkali conditions.

Vitamin K is found in nature in two forms—K1, also called phylloquinone, is found in plants; and vitamin K2, also called menaquinone, which can be synthesized by many bacteria. Vitamin K3, menadione, is a synthetic form of vitamin K which is manmade.

Vitamin K, a group of three related substances, is the last of the fat-soluble vitamins, completing the family that also includes vitamins A, D, E, and F. This nutrient, both found in nature and made in the body, helps phylloquinone, the natural vitamin K found in alfalfa and other foods.It was discovered in Denmark and labeled vitamin K for the Danish word Koagulation. Food-source phylloquinone is termed K1, while the menaquinone produced by our intestinal bacteria is labeled vitamin K2. A synthetic compound with the basic structure of the quinones is menadione, or vitamin K3. It has twice the activity of the natural Ks and is used therapeutically in people who may not use natural vitamin K well, such as those with decreased bile acid secretion.

All vitamin K variants are fat soluble and stable to heat. Alkalis, strong acids, radiation, and oxidizing agents can destroy vitamin K. It is absorbed from the upper small intestine with the help of bile or bile salts and pancreatic juices and then carried to the liver for the synthesis of prothrombin, a key blood-clotting factor. High intake (as with supplementation) of vitamin E or calcium may reduce vitamin K absorption. Vitamin K is stored in small amounts; most is excreted after therapeutic doses.

Vitamin K is used in the body to control blood clotting and is essential for synthesizing the liver protein that controls the clotting. It is involved in creating the important prothrombin, which is the precursor to thrombin—a very important factor in blood clotting. It is also involved in bone formation and repair. In the intestines it also assists in converting glucose to glycogen, this can then be stored in the liver. There are some indications that Vitamin K may decrease the incidence or severity of osteoporosis and slow bone loss.

A deficiency of this vitamin in newborn babies results in hemorrhagic disease, as well as post-operative bleeding and hematuria while muscle hematomas and inter-cranial hemorrhages have been reported. A shortage of this vitamin may manifest itself in nosebleeds, internal hemorrhaging.

Toxicity does not easily occur with normal dietary intake of this vitamin, but can happen if synthetic compound vitamin K 3 is taken. High to toxic uptake in the synthetic form can cause flushing and sweating. Jaundice and anemia may also develop. If you are taking anti-coagulant (to prevent blood clotting) medication, consult your medical practitioner before taking a Vitamin K supplement.

This nutrient can be destroyed by freezing and radiation as well as air pollution. Absorption may be decreased when rancid fats are present, as well as excessive refined sugar, antibiotics, high dosages of vitamin E, or calcium and mineral oils.

Vitamin K is found in leafy vegetables, cheese and liver. It is also found in asparagus, coffee, bacon and green tea. Yogurt, kefir, and acidophilus milk may help to increase the functioning of the intestinal bacterial flora and therefore contribute to vitamin K production.

Some people are of the opinion that it also promotes longevity.