Supplements & Herbs

Sponsored by Dr. Weil's Vitamin Advisor.

What is vitamin K?
Vitamin K is an umbrella term encompassing a group of chemically related fat-soluble compounds known as naphthoquinones. This group includes vitamins K, K1, K2, and K3. Vitamin K1 (phytonadione) is the natural form of vitamin K; it is found in plants and is the primary source of vitamin K that humans obtain through foods.

Why is vitamin K necessary?
Vitamin K is an essential nutrient necessary for blood clotting - it regulates normal blood clotting by helping the body transport calcium. Vitamin K may also be helpful for bone health: it may reduce bone loss, and decrease risk of bone fractures. It also may prevent calcification of arteries and other soft tissue.

What are the signs of a deficiency?
While rare, a deficiency in vitamin K can lead to defective blood clotting, increased bleeding and osteoporosis. Symptoms include easy bruising, gastrointestinal bleeding, excessive menstrual bleeding and blood in the urine. Those most at risk for a vitamin K deficiency include people with chronic malnutrition, those with alcohol dependency, and anyone with health conditions that limit absorption of dietary vitamins.

How much, and what kind, does an adult need?
Adults and children who eat a balanced diet that include the foods listed below will obtain enough vitamin K, and do not need supplementation. People who may benefit from supplemental vitamin K are babies (who usually get a shot of vitamin K at birth) and those with digestive diseases.

How much does a child need?
In an effort to prevent "hemorrhagic disease of newborn," also known as vitamin K deficiency bleeding (VKDB), a Vitamin K1 injection may be given to newborns and young infants. Otherwise, food sources should fill any daily needs.

How do you get enough vitamin K from foods?
Vitamin K is abundant in leafy greens, such as Swiss chard, kale, parsley and spinach, broccoli and cauliflower, Brussels sprouts, liver, soybean oil and wheat bran.

Are there any risks associated with too much vitamin K?
While no known toxicity is associated with vitamin K, high doses may cause numbness or tingling in the extremities.

Are there any other special considerations?
People taking prescription anticoagulants need to monitor their dietary intake of vitamin K closely, and should never take supplemental vitamin K.

Vitamin K supplementation during pregnancy (beyond normal dietary intake) may increase the risk of jaundice in newborns. Vitamin K ingested by breastfeeding mothers is generally considered safe.

High doses of aspirin and quinine may increase vitamin K requirements; antacids may decrease absorption of vitamin K, and vitamin K may decrease the blood thinning effects of several herbs including alfalfa, American ginseng, anise, celery, chamomile, horse chestnut and red clover.

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Is vitamin K right for you?
Everyone's dietary needs are different based on a number of factors including lifestyle, diet, medications and more. To find out if vitamin K is right for you, take Dr. Weil's Vitamin Advisor. This 4-step questionnaire requires just minutes to complete, and generates a free, no-obligation vitamin and nutritional supplement recommendation that is personalized to meet your unique nutritional needs.