Vitamin K is another fat-soluble vitamin that is vital to life. Vitamin K is primarily involved in blood clotting. Blood clotting is important in the body to prevent hemorrhage in times of injury or cut to the tissues. Imagine if you have a cut in your body and your blood clotting system does not work, you can bleed to death. This is why in cases such as surgery, your blood must be measured in terms of clotting time and if blood clotting is impaired, surgery may be withheld or postponed until Vitamin K is administered to ensure clotting and reduce bleeding during surgery. Calcium and certain proteins are also involved in the formation of blood clotting. For example, a protein precursor produced by the liver called Prothrombin, must be converted into an active form called Thrombin. With Vitamin K, Calcium ions bind Prothrombin to a lipid surface to produce this active protein (Thrombin) that forms a clot. Vitamin K also works with Vitamin D in the body by helping Vitamin D control Calcium levels. Other nutrients that interact with Vitamin K are Vitamin A and Vitamin E. Acting as antagonist, Vitamins A and E have been known to interfere with the absorption of Vitamin K in the body.

There are exceptions to this, however. For example, a condition called Hemophilia is a genetic defect that lacks the ability to produce certain clotting factors, thus preventing blood to clot and promoting hemorrhage. Such a condition is not curable by administration of Vitamin K; therefore, surgery becomes a difficult challenge among physicians. Another scenario is in cases like heart problems. People with a heart problem are mostly given medication (Coumadin or Warfarin) to thin their blood to prevent clots that can cause heart attacks. Therefore, supplementation of Vitamin K and intake of Vitamin K-rich foods must be restricted.

Being a fat-soluble vitamin, Vitamin K requires the presence of fat in order for it to be absorbed by the body. Therefore, similar conditions that lead to fat malabsorption (defects in the absorption of fat in the body) can also affect blood clotting due to the fact that Vitamin K formation is also affected.

Vitamin K has more than just one function and is also closely related to Vitamin D. For example, Vitamin K is involved in the making of Vitamin D in the body by way of synthesizing a certain bone protein that controls levels of Calcium in the blood. As mentioned earlier in the Vitamin D section, Calcium and Vitamin D work hand-in-hand. Besides food, Vitamin K is produced by some of the billions of bacteria in our intestines. It is believed that the body's need for Vitamin K is met by way of 50% from food sources and 50% from the intestinal bacteria.

Functions

• Important in blood clotting to prevent uncontrolled bleeding or hemorrhage
• Helps Vitamin D in controlling levels of Calcium in the blood

Deficiencies

Because Vitamin K is essential in blood clotting, deficiency of this vitamin can cause uncontrolled bleeding or hemorrhage. However, like Vitamin E, deficiency in Vitamin K is also not very well established. This is because under normal condition, the body's need for Vitamin K is very minute and half of the Vitamin K requirement is supplied from intestinal bacteria. However, there is an exception. Levels of Vitamin K are reported to be low in newborn infants because of two reasons. First, the intestinal tract of a newborn infant has not culminated for bacteria to settle down. Secondly, newly born infants are not fed right away and those that are fed with breast milk still pose risk of deficiency due to the fact that breast milk is a poor source of Vitamin K. Therefore, newborn infants are supplemented with synthetic Vitamin K. People who have taken or are taking antibiotics to fight infection (which kills intestinal bacteria) may have low levels of Vitamin K and also require Vitamin K supplementation. Both conditions may predispose this population to hemorrhage due to the fact that blood clotting is affected.

Toxicity

Fat-soluble vitamins can reach toxic levels when taken in excessive amounts. Although Vitamin K is a fat-soluble vitamin, it is not toxic if the amount is from natural sources. Toxicity has been reported mostly from excessive supplementation of a synthetic source of Vitamin K. Such toxicity is believed to cause the liver to produce bile pigment, and cause destruction of the red blood cells, thus releasing them into the blood stream resulting in jaundice (yellow skin) and brain damage.

The Recommended Dietary Allowance (RDA)

The Recommended Dietary Allowance (RDA) for Vitamin K is expressed in micrograms (mcg).

Food Sources

-- Ofelia B. Mutia, M.S.,R.D.,L.D.

Resources and Acknowledgments

1. Understanding Normal & Clinical Nutrition by Whitney, Cataldo & Rolfes
2. The Essential Guide to Vitamins and Minerals by Elizabeth Somer, M.A.,R.D.
3. Nutrition Concepts & Controversies by Hamilton, Whitney & Sizer
4. Advanced Nutrition and Human Metabolism by James L. Groff, Sareen S. Gropper
5. Bowes & Church's Food Values of Portions Commonly Used by Jean A.T. Pennington, Ph.D., Anna De Planter Bowes, Helen N. Church
6. Essentials of Nutrition and Diet Therapy by Sue Rodwell Williams