Dispelling nutrition myths, ranting, and occasionally, raving


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Everything you want to know (and probably more) about vitamin K

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No ranting today. No raving either. A little while ago, a friend asked me to write a post about vitamin K-rich foods. So, this post is just straight-up info for those who are interested in learning more about vitamin K.

You may be wondering, “What is vitamin K?” (if you’re not, feel free to skip on ahead to the next paragraph). Vitamin K is a family of compounds including phylloquinone (vitamin K1) which is found in plants, and menaquinones (vitamin K2) which are found in fish oils and meats (thanks old nutrition textbook: Perspectives in Nutrition by Wardlaw and Hampl).

Vitamin K is essential for blood clotting. Fun fact: the Danish researcher who discovered the relationship between vitamin K and blood clotting named it for the word “koagulation” (which, in case you couldn’t guess, translates to “coagulation” in English). The adequate intake for women is 90 mcg a day, for men, 120 mcg, based on typical adult intakes. In addition to food sources of vitamin K, microorganisms in our intestines also produce vitamin K.

Although, vitamin K is a fat soluble vitamin, there is no upper limit set for consumption as it tends to disappear from the body within a few days of consumption. However, high dose supplements are not recommended as the synthetic form of vitamin K is far more potent than the naturally occurring forms as has been found to cause hemolytic anemia in rats and severe jaundice in infants. Vitamin K deficiency is also relatively uncommon. It’s most likely to be seen in people who have fat malabsorption (e.g. celiac disease or some types of bariatric surgery), long-term antibiotic use, or seniors with little consumption of leafy green vegetables. Newborn infants are routinely given vitamin K injections within 6 hours of delivery as they are at risk of defective blood clotting and hemorrhaging as a result of vitamin K deficiency. It’s important for people taking blood thinners, and some other medications, to consume consistent (or limit) amounts of vitamin K containing foods to ensure efficacy of the medications.

As alluded to above, leafy greens are the primary dietary source of vitamin K. Kale tops the list at 530 mcg per 1/2 cup (cooked), followed by turnip greens (520 mcg per cup), spinach (480 mcg/cup), brussels sprouts (150 mcg per 1/2 cup), raw spinach or cooked asparagus (144 mcg/cup), cooked broccoli (110 mcg for 1/2 cup), and looseleaf lettuce (97 mcg/cup). Other good sources of vitamin K include: cooked green beans (48 mcg per 1/2 cup), raw cabbage (42 mcg/cup), sauerkraut (30 mcg per 1/2 cup), green peas (26 mcg per 1/2 cup), soybean oil (25 mcg/tbsp), and cooked cauliflower (20 mcg/cup).