When people think of vitamin K, they often relate it to blood clotting—and this is an accurate association because this vitamin is required in the synthesis of several blood proteins involved in clotting, says Nijya Saffo, RD, registered dietitian and owner of NK Fitness and Nutrition, LLC. Besides this, another key role of vitamin K is the activation of proteins needed for bone metabolism (the replenishment of bone tissue).
Vitamin K is the collective name of a family of compounds. "There are different categories within vitamin K," says Rayanne Nguyen, RD, registered dietitian specializing in sports nutrition. "You have vitamin K1, which is found in dark leafy greens and soybean oil, and also vitamin K2 and some others, which can be found in smaller amounts in animal products." Fermented foods also contain vitamin K2.
As a fat soluble vitamin, vitamin K from food appears to be absorbed best when there's fat or oil in the same environment. So when you're having your green vegetables, toss it in some oil to increase its absorption.
Your body treats vitamin K like a fat and stores it in your liver and fat tissues. "We can rely on our body stores a little bit more than [we can for] some of our water soluble vitamins," says Nguyen. But at the same time, your body isn't able to make enough vitamin K consistently, and relies on you getting it from your diet.
The Daily Value for vitamin K is 90 micrograms. "If someone has a disease that impacts the gastrointestinal tract, like celiac disease or Crohn's disease, they may not absorb the vitamin K from their food as well," says Nguyen. In these cases, the physician and dietitian would monitor the person's vitamin K levels more regularly and may start them on a supplement.
There are also people who need to be more mindful about their intake of vitamin K-rich foods. Since vitamin K supports blood clotting, if you are on a medication to prevent clotting, sudden increases in vitamin K intake may interfere with your medication, says Saffo. "There's no evidence that you have to stop eating vitamin K foods when you're on these kinds of medications, but you don't want to overdo it and suddenly start taking vitamin K supplements or eat large amounts of foods with vitamin K in it."
If you want to keep your vitamin K intake steady or check whether you're having enough, we have rounded up the best food sources of vitamin K below.
Foods High in Vitamin K
There are 113 micrograms in a cup of uncooked kale, providing 94 percent of the DV. Roast your kale with a drizzle of olive oil and a dash of salt to enjoy a crunchy, high-vitamin K snack.
This is a sign to whip out a Southern-style collard greens recipe now and again. A half cup serving of cooked collard greens provides over 400 percent of the DV of vitamin K (530 micrograms).
These bitter greens seem to have an edge when it comes to vitamin K. There are 286 micrograms in half a cup of cooked swiss chard (over 200 percent of the DV).
If you prefer something with a milder, less bitter flavor, a cup of uncooked spinach is another option, with 145 micrograms (120 percent of the DV).
Just half a cup of cooked broccoli already contains 110 micrograms, or 92 percent of the DV. Pair it with some cheese (fat!) to boost the vitamin K absorption.
Brussels sprouts hold 109 micrograms of vitamin K in half a cup, which meets 91 percent of the DV. Toss these in olive oil and salt, and roast until tender on the inside and crispy on the outside.
Having a large salad with two cups of romaine lettuce (hello, dinner caesar salad!) would give you 120 micrograms, or 130 percent of the DV, of vitamin K.
Garnishing your bowl of soup with one tablespoon of fresh parsley offers you 62 micrograms, 50 percent of your daily vitamin K needs.
If you're already having a daily dose of prunes for gut health, you'd be pleased to know it also offers vitamin K. A snack of six prunes contains 35 micrograms or 30 percent of the DV.
Per tablespoon, soybean oil, a vegetable oil extracted from the seeds of the soybean, contains 25 micrograms or 20 percent of the DV. It also provides you with alpha-linolenic acid, a type of omega-3 fat that's important in eye and nerve development.