Vitamin K-The K vitamins are a group of related chemical compounds. Below is an illustration of the molecule common to all forms of vitamin K.
Vitamin K. There are several forms of vitamin K. However, they must be converted to hydroquinone (the active form of the vitamin to perform its function in the process of clotting).
Vitamin K is required for the hepatic (liver) synthesis of prothrombin and blood clotting factors I, VII, IX, and X. I, VII, IX, and X are Roman numerals for the numbers 1, 7, 9, and 10, respectively.
Prothrombin and the blood clotting factors are proteins which are manufactured in the liver. These proteins are intentionally manufactured "incomplete". If they were manufactured completely, unwanted clotting could occur. When "activity" is needed (eg., during a bleeding episode, due to cutting of the skin, etc.), prothrombin is made "active" by the carboxylation (adding CO2) of its glutamic acid residues. Glutamic acid (abbrev., Gla) is one of the 20 amino acids that the human utilises, reviewed in proteins. The carboxylation of glutamic acid residues is vitamin K-dependant. The overall reaction requires prothrombin, the hydroquinone form of vitamin K, O2 and CO2.
This reaction is essential in the clotting cascade. After carboxylation of the glutamic acid residues of prothrombin, they are now strong attractants to phospholipids on the platelet surface. Platelets play a role in coagulation (clotting).
In all probability, there are other important functions of vitamin K that we have not yet elucidated. Glutamic acid residues are found in proteins unrelated to the clotting cascade, and these may undergo reactions with hydroquinone (vitamin K) as well. Therefore, keep in mind that vitamin K, as with other vitamins most likely serve many other purposes, as we shall verify with more research. In any event, vitamin K is required in the clotting cascade, and this is vital to survival. Clotting not only serves to prevent blood loss when we superficially injure ourselves. Clotting is a process that occurs constantly in all areas of the body as a result of microscopic insults, such as minor internal day to day traumas, wear and tear, and even to stop internal bleeding from undetected genetic anomalies of the circulatory system. Deficiency of vitamin K can lead to bleeding tendencies, increased clotting times, and other anomalies.
Sources of vitamin K
Good sources of vitamin K are spinach, cauliflower, cabbage (uuuggh !!), egg yolk, and liver. Normal bacterial flora residing in the gut also synthesize vitamin K for us! Amounts vary though, considering the type of bacterial populations differ in individuals. Therefore, although it is beneficial that bacteria help us with some vitamin K production, we should not rely on it entirely, since amounts vary per individual. Rather we should rely on a proper diet to ensure adequate amounts of each nutrient.
Did you know?
In practice, even newborns are given an injection of vitamin K to help them on their way, since they haven't had the chance in utero (in the womb) to establish their bacterial flora.
RDA of vitamin K
There is no established RDA for vitamin K. However, 70 to 140 micrograms/day is the recommendation. The lower level of 70 micrograms assumes bacterial synthesis from gut bacteria, and the upper limit recommendation of 140 micrograms assumes no bacterial contribution. Again, this is controversial, and a little extra vitamin K is not harmful.
Deficiency of vitamin K
Vitamin K deficiency in the adult is rare. This is because of its wide distribution in food sources and the varying contribution from bacteria. It can be observed in areas of poverty and in malnutrition. Deficiency is characterized by a prolonged clotting time, and this can sometimes be seen in newborns of any economic background. This is why infants are given an injection of vitamin K, as discussed above.
Toxicity of vitamin K
Administration of large doses of vitamin K can cause haemolytic anaemia, hyperbilirubinaemia [increased amounts of bilirubin (breakdown product of haemoglobin from the red blood cell) in the blood] and jaundice of the newborn due to toxic effects imposed on the membrane of the red blood cells. Newborns can also develop an enlarged liver. In the adult, excessive doses can cause a decrease in liver function and hypoprothrombinaemia (decreased prothrombin synthesis).
Total dose should not exceed 3 mg (milligrams) of menadiol or 1 mg of menadione. With an increase of companies selling injectable vitamins, extreme caution should be taken. With this "in vogue" trend increasing in the hopes of the best health, there are certain countries which allow injectable vitamins to be purchased without a doctors advice or prescription. There is really no place for injectable vitamins, with exception to newborns (discussed above), or with a medical condition (eg., vitamin B12 malabsorption). Along with the general risks of injecting, there are other dangers. For example, regarding vitamin K, IV (intravenous) administration has caused deaths at injection rates greater than 1 mg per minute (in other words, injecting the load in too quickly). It is always best obtaining nutrients through diet, unless an existing medical condition dictates otherwise.