What's so Special About Vitamin K?

Vitamin K may not be as well-known as, say, Vitamin C or the B vitamins, but it is just as important to our health. Vitamin K is a generic term, a group word that refers to different types of compounds. The most common types are K₁ and K₂. We obtain vitamin K₁ from the diet. Type K₂ is synthesized in our body by naturally-occurring bacteria in the intestines. However, the amount of vitamin K produced in our intestinal system is not enough: We need a varied and balanced diet to make sure that we meet the daily requirements in vitamin K.

Vitamin K is a fat-soluble vitamin, which means that it is absorbed with fat from the food we eat. It is stored in the liver and in fatty tissue. Its name derives from the German term Koagulationsvitamin (clotting vitamin) because it plays an important role in the chemical reactions that ensure blood clotting. Hemostatic balance is achieved a) when the clotting process (the coagulation cascade) is activated to stop bleeding, but also (and just as importantly) b) when clotting is kept under control. Vitamin K is of vital significance to that balance because it helps the liver produce both clotting proteins (which are called vitamin K-dependent clotting factors) and natural anticoagulants (proteins C and S). There is also evidence that vitamin K may promote bone density and help prevent and repair osteoporosis.

There is a vast array of natural dietary sources of Vitamin K: spinach, lettuce, cabbage, cauliflower, broccoli, kale, collards, parsley, asparagus, soybeans, organ meats (liver), wheat bran, eggs, dairy products, strawberries, bananas. Make sure that your daily diet includes 3-4 servings of fruits and vegetables, and there should be no need for supplements.

As a matter of fact, vitamin K deficiency is pretty rare, and when it does happen it is mostly because of conditions that prevent the production or absorption of the vitamin. Vitamin K deficiency can occur because of long-term anticoagulant therapy, chronic use of certain antibiotics that kill the intestinal flora that produces vitamin K, alcohol dependency, liver disorders, and malabsorption disorders (i.e. disorders that impair the absorption of fats, and thus of vitamin K). Newborns are also at risk for vitamin K deficiency because their intestine is sterile and does not synthesize this vitamin. Newborn infants are given vitamin K by injection, while major-brand formulas are vitamin K-enriched.

If you are considering taking vitamin K supplements, please consult your physician to avoid side-effects. This is especially important if you are taking anticoagulants (esp. warfarin), as vitamin K may interfere with the effects of warfarin. Consult your physician and clinical dietitian to make sure your diet includes foods with the vitamin K content that is right for you.