Vitamin K is essential for blood clotting and bone maintenance, and can be obtained from green leafy vegetables or synthesized by gut bacteria. Malabsorption syndrome, liver disease, and antibiotic use can reduce absorption. Vitamin A and E supplements and anticoagulant therapy drugs can also interfere with absorption. Patients on blood thinning therapy should consult with their doctor about their vitamin K levels.
Vitamin K is one of the essential fat-soluble vitamins necessary for human health. In particular, it is essential for proper blood clotting and maintenance of skeletal bone. Sources of vitamin K include green leafy vegetables in the diet for one form of the vitamin and synthesis by gastrointestinal tract bacteria for another. The required amount of vitamin K ingested from diet or supplements is usually small because the body recycles the available compound in an almost infinite cycle. Despite this recycling, any changes to the body’s ingestion or storage of this nutrient — or to the synthesis of the compound by gut bacteria — can affect vitamin K absorption.
For the food source, the absorption of vitamin K occurs in the small intestine. Diseases of the small intestine or the surgical removal of part of this organ can reduce the absorption of nutrients and vitamins in a condition known as malabsorption syndrome. Digestion of all fat-soluble vitamins requires a necessary amount of pancreatic and biliary enzymes as well as dietary fat to facilitate their absorption. Therefore, liver disease, gallbladder disorders or pancreatic disease may reduce absorption. A low-fat diet can also reduce the body’s ability to absorb vitamin K.
The liver is intimately involved in the absorption, storage and recycling of vitamin K. Not only is it the main depot of stored vitamin K, but it produces digestive enzymes – bile salts – which are needed to metabolize dietary food into vitamin K. Any type of liver disease can reduce the absorption of vitamin K. This can happen by decreasing the liver’s production of bile salts needed for digestion or by decreasing the organ’s storage capacity due to scarring or inflammation. Liver involvement in blood clotting outside of the vitamin K cycle means that disease may require vitamin K replacement as clotting factors are reduced or eliminated.
For intestinal bacterial synthesis source of vitamin K, long-term use of broad-spectrum antibiotics can reduce absorption by eliminating beneficial bacteria. This unfortunate side effect is sometimes the result of treating cystic acne, recalcitrant sinus infections, and other antibiotic therapies that require weeks or months of medication. Partial surgical removal of the small or large intestine can also result in this loss of absorption through the loss of bacterial production.
Finally, medications and dietary supplements may also interact to reduce vitamin K absorption. Vitamin A, in particular, interferes with vitamin K absorption, and supplemental vitamin E may require increased amounts of vitamin K using dependent clotting factors from vitamin K. Anticoagulant therapy drugs such as warfarin disrupt the body’s natural recycling cycle for vitamin K.
There are differing opinions as to whether patients on anticoagulant therapy can use vitamin K safely. Traditionally, patients using medications such as warfarin have been advised to avoid vitamin K supplements due to the risk of blood clots. Some scientists believe that a moderate intake of vitamin K may not be harmful. Patients using blood thinning therapy who are concerned about their vitamin K levels should speak to their doctor to get the best and most accurate advice for their situation.
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