You may perceive vitamins as harmless nutritional aids, but it's smart to seek information about possible interactions between the vitamins you take and the prescription medications your doctor prescribes. Interactions between drugs and vitamins can weaken the effectiveness of your prescriptions, affect your ability to properly absorb nutrients, or in some cases increase the effects of your medications, which can be particularly dangerous. Vitamin K is no exception. Consult your doctor before taking vitamin K supplements or eating foods that are rich in the vitamin if you are on prescription medication.
Types of K
There are three forms of vitamin K. Vitamin K-1, also known as phylloquinone, is naturally present in foods such as leafy green vegetables. A synthetic form of K-1, called phytonadione, is used to treat vitamin K deficiency and bleeding disorders. K-2, or menaquinone, is produced by bacteria in your gastrointestinal system, although the amounts produced are not sufficient to meet your nutritional needs. K-3, or menadione, is a synthetic form of vitamin K used in animal feed, and can be toxic to humans. The FDA has banned K-3 supplements in the United States.
Functions
Vitamin K's only known purpose is to aid in the formation of blood clots. Although some alternative health practitioners tout vitamin K as a cancer-fighting agent, the American Cancer Society states that there is no scientific evidence to validate the use of this nutrient as a form of cancer therapy. Vitamin K is also used in cosmetics to decrease the appearance of broken blood vessels and skin irritation, but this use has not been scientifically proven to be effective.
Drug Interactions
A number of medications can interact with vitamin K in ways that can alter their effectiveness and impact your health. Warfarin, brand name Coumadin, for example, is prescribed to reduce blood clotting in people who are at risk for stroke. Vitamin K may counteract warfarin's effectiveness. Some drugs, such as the weight-loss drug Orlistat, antibiotics and bile acid sequestrants, can decrease your body's ability to absorb vitamin K.
Considerations
Vitamin K deficiency is rare, thanks to the ready availability of this nutrient in foods such as beef liver, green tea, broccoli, spinach and dark green lettuce. Vitamin K is a fat-soluble vitamin, and those with disorders that affect their ability to digest fats are at increased risk of K deficiency. Newborn infants are vulnerable to K deficiency as well, because they don't yet have the normal intestinal flora that produce it, and breast milk has a low K content. Vitamin K deficiency in infants can be fatal when birth trauma causes intracranial hemorrhaging.
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