There’s a lot of buzz about vitamin K and whether or not people consuming plant-based diets get enough of all its forms. Just what is it that makes this nutrient so important, and do you really have to worry about being deficient?
What is Vitamin K?
Vitamin K is a fat-soluble vitamin “family” that includes three forms:
- Phylloquinone (K1), found in plant foods
- Menaquinone (K2), found in animal foods and formed in the body from phylloquinone
- Menodione (K3), a synthetic form often used in supplements
Why Do We Need Vitamin K?
Vitamin K has several “jobs” in the body:
Supports bone health
Interactions between vitamin K and specific cells and proteins keep bones healthy and strong. Vitamin K aids in bone health in two ways: It moderates the function of osteoclasts, cells involved in bone demineralization, and it converts osteocalcin, an important protein in bone, to its active form, allowing it to bind with calcium so that the mineral stays in the bones where it belongs.
Aids blood clotting
By modulating the enzymatic processes involved in the production of clotting factors, vitamin K ensures that blood doesn’t clot too little or too much.
Prevents arterial calcification
Calcium deposits in blood vessels are responsible for the hardening of arteries that is the precursor to to heart disease. Vitamin K aids in the activation of proteins responsible for blocking this process.
Other benefits of getting your daily dose of K:
- Brain and nerve support
- Prevention of oxidative damage
- Inhibition of cancer cell growth
- Regulation of inflammation
Where Do We Get Vitamin K?
Common plant-based sources of vitamin K include:
So remember, for vitamin K, eat lots of kale—and other leafy greens! If you’re particularly fond of brassicas, also called cruciferous vegetables, you’ll have no trouble getting enough of this important nutrient.
How much vitamin K do you need?
The daily recommended intake (DRI) for vitamin K is 120mcg/day for men and 90mcg/day for women..
Although vitamin K, like other nutrients, is best obtained from foods, it may be supplemented therapeutically for certain conditions, including osteoporosis. Therapeutic doses range from 100-500mcg/day. High-dose supplementation should always be overseen by a health professional.
Since vitamin K is a fat-soluble vitamin, your body is better able to absorb it if you include a healthy fat source along with your leafy greens. Sprinkle raw nuts or seeds on salads, add ground flax to soups and stews or try one of these delicious recipes:
- Creamy Cashew Ranch Dressing from In Sonnet’s Kitchen
- Sam’s Sweet Potato Almond Butter Sauce
- Melty Stretchy Gooey Vegan Mozzarella from It Doesn’t Taste Like Chicken
Do Gut Bacteria Play a Role?
Your body needs both vitamin K1 and K2 for optimal health. Evidence shows gut bacteria do synthesize some vitamin K2 from dietary sources of K1, and antibiotic use can affect the level of production by reducing the overall population of bacteria. However, there’s currently no hard science showing where in the intestines this conversion takes place and whether or not humans are able to absorb enough from the process to meet nutritional requirements.
Other studies demonstrate K2 is created from K1 in peripheral body tissues, suggesting direct consumption of K2 may not be necessary. The only substantial plant-based source of K2 is natto, a fermented soybean product that’s not a big hit in the Western world, although after trying some myself recently, I’d like to point out that it isn’t as bad as some descriptions make it sound.
The jury is still out on whether or not the body converts enough vitamin K1 to vitamin K2 to meet nutritional needs. Until more extensive studies are done on people who have been eating exclusively plant-based diets for years, we probably won’t know for sure how well the conversion works or if a healthier diet may improve the ability to convert the vitamin from one form to another. My advice is to consume a variety of whole plant foods every day, including lots of leafy greens, and avoid processed junk that can interfere with the natural processes your body uses to stay healthy.
(As an aside, it seems strange to me that our gut bacteria — or anything in our bodies — would produce a nutritional compound we can’t or don’t utilize in some way. I’ll be interested to see what science uncovers about vitamin K conversion as more plant-based populations are studied!)
Bauman, E., Friedlander, J. (2013). NC202 Men and Women’s Health. Therapeutic Nutrition Part I. Penngrove, CA: Bauman College
Bauman, E. NC106.4 Micronutrients: Intro to Vitamins, the Fat Soluble Vitamins A, E, D, &K [PowerPoint Slides]. Retrieved from Bauman College: http://dashboard.baumancollege.org/mod/resource/view.php?id=1454
Murray, M., Pizzorno, J., Pizzorno, L. (2005). Vitamins. The Encyclopedia of Healing Foods. New York: Simon and Schuster
Vitamin K (n.d.). In World’s Healthiest Foods. Retrieved November 22, 2013, from http://www.whfoods.com/genpage.php?tname=nutrient&dbid=112