What is Vitamin K and do I need a supplement?
Vitamin K is a fat-soluble vitamin. It helps make four of the 13 proteins you need for blood clotting. Recently, researchers have shown that vitamin K is also involved in building bone. Low levels of circulating vitamin K have been linked with low bone density. The Nurses’ Health Study demonstrated that women who consume the highest intake of vitamin K were 30 percent less likely to break a hip than women who consumed less in their diets. Researchers at Tufts University in USA found that only 50 percent of people get enough from their diets.
How much do I need?
The average male needs 120 mcg (micrograms) and women need 90 mcg each day. Children 1-3 years of age require 30 mcg; ages 4-8 need 55 mcg. Kids, ages 9-13 years need to aim for 60 mcg, and ages 14-18 years need 75 mcg.
People who take anticoagulants such as warfarin (Coumadin) are generally advised to keep their Vitamin K intake stable due to its role in clotting. It is important to note the synthetic forms of the vitamin, which might be found in vitamin supplements, can be toxic at very high intakes. The upper intake level of vitamin K can not be determined due to lack of data of adverse effects and concerns with regards to the body’s lack of ability to handle excess amounts. Sources of vitamin K should be from food only to prevent high levels of intake.
Where do I get it?
Millions of good bacteria in your intestinal tract do synthesize this vitamin. Once you absorb this manufactured vitamin K, it gets stored in the liver. The body conserves it very carefully and this is the reason that vitamin K deficiency is hardly ever seen. People who have had long-term antibiotic treatment, who have chronic inflammatory bowel disease or are taking cholesterol lowering drugs may have problems absorbing this vitamin.
Our diet provides us with lots of vitamin K. Leafy green vegetables are by far the best food sources of this nutrient. Vitamin K is found in kale, spinach, collard greens, broccoli, Brussels sprouts, cabbage, lettuce, asparagus, peas and parsley. It is also found in lentils, split peas, milk and soybean oil. One half cup serving of cooked kale provides more 1.5-2 times the recommended intake.
So don’t supplement with Vitamin K. You get enough in your diet!
Samara’s Favourite Saute’ Kale, makes 4 servings
This simple vegetable side dish provides 180 mcg vitamin K
2 tsp (10 mL) olive oil
1 tsp (5 mL) sesame oil
4 cups (1 L) kale, julienned (tough center rib remove first)
2 leeks, julienned (white and light green parts only)
1 Tbsp (15 mL) tahini
2 tsp (10 mL) hot pepper sauce
2 tsp (10 mL) soy sauce, low sodium
In a wok or large skillet, heat olive oil and sesame oil over low-medium heat. Add kale and leeks; stir-fry for 3-5 minutes or until limp. Combine tahini, hot pepper sauce and soy sauce; pour over vegetables. Season with pepper if desired. Note: spinach is delicious too when cooked this way.
Adapted from: Dietitians of Canada “Simply Great Food”, Robert Rose, 2007