Vitamin K

The Fat Soluble Vitamins · Vitamin A · Vitamin D · Vitamin E · Vitamin K The Water Soluble Vitamins · The B-Group Vitamins · Thiamine - Vitamin B1 · Riboflavin-Vitamin B2 · Pantothenic Acid - Vitamin B3 · Biotin - Vitamin B4 · Nicotinic Acid (Niacin) - Vitamin B5 · Pyridoxine - Vitamin B6 · Cyanocobalamin - Vitamin B12 · Ascorbic Acid - Vitamin C

Vitamin K exists in nature in two forms - K1 and K2, but only vitamin K1 is of importance nutritionally.  Natural Vitamin K1 is yellow oil, soluble in fat solvents, but only slightly in water.

Physiological Action
Vitamin K is necessary for the synthesis of at least two proteins involved in blood clotting.  One of them is prothrombin, a glycoprotein present in plasma and necessary for normal blood clotting.  It is also required along with Vitamin D to regulate blood calcium levels.

If blood-clotting time is too long then wounds may bleed for prolonged periods. This is especially important when undergoing surgery.  Internal synthesis of Vitamin K occurs in the intestinal bacteria and this provides the body with about half of it's daily  requirements.

Deficiency
In adults deficiency has never been clearly demonstrated, except where severe fat malabsorption exists.  In infants, however, whose intestinal tracts are sterile and thus have no internal production of Vitamin K and in adults on prolonged doses of antibiotics, which kill intestinal bacteria, Vitamin K deficiency does occur and sometimes supplements are necessary.

Toxicity
Does not occur from amounts commonly consumed from natural sources.  Toxicity can result when supplements of a synthetic version of Vitamin K are given, especially in infants and pregnant women.

Symptoms include the breakdown of the red blood cells, releasing their pigment into the skin (jaundice) and also causing brain damage.

Dietary Sources
Dark green leafy vegetables and liver are the main food sources.

Therapeutic Uses

1. In bleeding diseases of the newborn - water soluble Vitamin K analogue is often used soon after birth to treat bleeding disorders due often to birth trauma.
2. In biliary obstruction or malabsorption Vitamin K preparations are invaluable in cases where absorption has been impaired by lack of bile salts, pancreatic secretion or other cause of digestive failure.
3. In anticoagulant therapy - when drugs used in such therapy decrease the blood clotting time enough to cause bleeding then Vitamin K intravenously or orally may be necessary.

Recommended Dietary Intake
Is best expressed as 2 micrograms/kgm of body weight/day, but about half of this could be produced by gut bacteria.