Each of the 13 essential vitamins plays an integral role in our health; however, it often feels like we hear about the same ones over and over—like vitamin C, which is hailed for its immune-supporting benefits, and vitamin D, a superstar for immunity, mood, bone health and more.
One all-important vitamin that we don’t hear about all that much is vitamin K. This often-overlooked nutrient plays a crucial role in our body, especially when it comes to the creation of proteins required to build bones and help blood clot, explains dietitian Emma Laing, Ph.D., R.D.N., director of dietetics at the University of Georgia and national spokesperson for the Academy of Nutrition and Dietetics. Compared to other key nutrients, many people don’t know much about vitamin K at all, let alone what the differences are between its different forms, namely K1 and K2. Here, we break it all down.
The two types of vitamin K
Vitamin K isn’t really just one single nutrient. To understand how the fat-soluble nutrients we umbrella under the term “vitamin K” impact our health, it’s important to suss out the differences between vitamin K1 and vitamin K2. Here’s a look at the role each type of vitamin K plays in the body.
This type of vitamin K, also known as phylloquinone, is the most common, accounting for 75 to 90 percent of the vitamin K consumed in the standard Western diet.
“K1 is important for bone and heart health, but especially blood clotting,” notes functional nutritional therapy practitioner Tansy Rodgers, F.N.T.P. Specifically, our body needs vitamin K1 to produce the proteins that help clot blood. Without vitamin K1, even a paper cut could lead to massive bleeding, Maria Zamarripa, M.S., R.D., owner of FoodFarmacistRD, previously told What’s Good. Ultimately, its role in blood clotting makes vitamin K1 a key player in wound healing.
Luckily, given its life-saving responsibilities, vitamin K1 is easy to get from food. You’ll find loads of it in various greens, particularly collards, kale, and spinach.
Important to know, though: Anyone taking anticoagulant medications that help prevent blood clots should actually avoid foods rich in vitamin K1 and talk to their healthcare provider about healthy vitamin K1 intake for them. (Since vitamin K1 promotes blood clotting, it essentially works against these medications.)
Vitamin K2, meanwhile, actually encompasses a number of compounds called menaquinones (referred to as MK-n). It plays a crucial role in calcium metabolism and, as such, is known for its ability to promote bone health and long-term cardiovascular health.
On the bone front, K2 is key for supporting healthy bone density, which is a must for avoiding osteoporosis, fractures, and other injuries throughout the years, according to Zamarripa. Case in point: According to research on postmenopausal women with osteoporosis published in The Journal of Obstetrics and Gynaecology Research, those who took 45 milligrams of vitamin K2 with 1,500 milligrams of calcium per day saw a significant increase in lumbar bone mineral density.
K2’s role in getting that calcium into bones also does your cardiovascular system good because that means less calcium is hanging around to potentially build up in your arteries, Zamarripa notes.
Certain sub-types of K2, specifically MK-7 through MK-11, are actually produced by gut bacteria within the body. You’ll also find the K2 sub-type MK-7 in fermented foods, such as sauerkraut and natto (a traditional Japanese food made from soybeans), though the amount can vary depending on the type of bacterial strains and fermentation process used, explains Laing. Meanwhile, you’ll find the sub-type MK-4 in animal sources, such as grass-fed meat, organ meats (mainly liver), egg yolks, and high-fat dairy products (mainly hard cheeses made with whole milk).
Fun fact: Recent research suggests that Jarlsberg cheese, which is a Norwegian cheese made from cow’s milk, seems to have unique benefits for supporting bone health because of its vitamin K2 content.
Are You Getting Enough Vitamin K?
When you see intake recommendations for vitamin K, they’re specifically focused on vitamin K1. The going rate is 90 micrograms per day for women and 120 for men, according to the National Institutes of Health (NIH).
Though a variety of foods are rich in vitamin K1, many people still fall short on it. Just one in 10 adults eats the recommended two to three cups of vegetables per day, meaning many people don’t chow down on enough of those K1-loaded leafy greens, per research by the Centers for Diseases Control and Prevention (CDC).
Then, in addition to the amounts produced in your gut, you can get your fill of vitamin K2 from a number of different foods. The tricky thing about vitamin K2, though, is that there’s no official recommended intake right now because it’s difficult to test people’s status and research around how much we really need is still developing. That said, research does suggest most people could benefit from consuming more vitamin K2 than many currently get. This is especially true for those with heart and bone health concerns, says functional dietitian Jenna Volpe, R.D.N., L.D., C.L.T.
Who else might need more? In general, research shows that older Americans are the most likely to be running low on vitamin K. However, those with underlying medical conditions that impact fat-soluble nutrient absorption, such as cystic fibrosis, celiac disease, ulcerative colitis, and other digestive disorders also have a high risk of falling short, explains The Vitamin Shoppe nutritionist Brittany Michels, R.D.N., C.P.T.
How to get the vitamin K you need
The best way to get vitamin K is by eating foods naturally abundant in K1 and K2 regularly. Your body can store vitamin K in your liver, so you don’t have to go all in on these foods every single day. Just make sure that green leafy vegetables, soybeans, grass-fed meat, full-fat grass-fed cheese, and eggs make regular appearances on your plate.
If you’re unable to include vitamin K foods on a consistent basis, ensure your daily multivitamin covers your baseline needs, or consider a vitamin K supplement. Michels recommends Vthrive Bioactive Immune Multivitamin with Elderberry & NAC, a multivitamin that contains vitamin K, or The Vitamin Shoppe brand Vitamin K Complex.
“If your supplement regimen includes a solo vitamin D but not a vitamin K-inclusive multivitamin, consider switching to a D3-K2 option like The Vitamin Shoppe brand Vitamin D3 & K2,” she adds. After all, you need both vitamin D and vitamin K2 to support calcium metabolism!
Just note that if you take any blood-thinning medications, you’ll need to chat with your doctor about how you should adjust your diet to avoid excess vitamin K1.