Often confused with vitamin K1 or simply overlooked, vitamin K2 is a unique form of an essential micronutrient that plays an important role in heart health. Let’s take a look at how much vitamin K2 you need, where you can get it, and potential benefits and side effects. The richest food sources of vitamin K1 include green leafy vegetables like kale, collards, spinach, Swiss chard, and turnip greens. Broccoli and Brussels sprouts are lesser known, but excellent sources of phylloquinone too. These diverse greens are nutrient-dense foods that most of us could use more of in our diets. While vitamin K1 sources are plant-based, vitamin K2 foods come mostly from animals—namely egg yolk, dairy (e.g., butter and particular cheeses), chicken, eel, and organ meats. Vitamin K2 is also found in certain fermented foods, with sauerkraut, kefir, and nattō (fermented soybeans) being the most famous. If you have taken antibiotics (and not replenished good gut bacteria through prebiotic and probiotic sources) or have suffered from gut infections or food sensitivities, you may not be producing as much vitamin K2. No scientific consensus nor dietary recommendations exist for vitamin K2 (yet). As more research builds3, a recommendation specific to menaquinone vitamin K sources may be warranted in the future. Even though vitamin K is fat-soluble, it turns out that what we consume and synthesize is quickly utilized, metabolized, and excreted4 by our body. Add in the fact that very little vitamin K is stored, and it becomes clear why consuming the right foods is important to achieve daily vitamin K needs. Targeted supplementation can also be a useful strategy (we’ll discuss that later). People taking anticoagulant therapy (i.e., blood thinners) and those with liver disease or fat malabsorption disorders are at higher risk of experiencing vitamin K deficiency. Not getting enough vitamin K (and specifically K2) over time may contribute to chronic health conditions6 like osteoporosis (lower bone mineral density due to bone loss) and cardiovascular disease. Heart disease is the leading cause of death7 in the United States. And while the condition is known as the “silent killer,” vitamin K2’s important role in heart health should no longer remain silent. Calcium plaques in your blood vessels can lead to serious (even fatal) blockages, which can manifest as angina, heart attack, and stroke. So, coronary calcification is something to be aware of and mitigate. Enter vitamin K2, your calcium “usher”. Vitamin K helps direct calcium9 to correct and beneficial places for your health (e.g. bones), keeping it away from the wrong places that can be detrimental to your body, particularly soft tissues like blood vessels. In this way, adequate vitamin K: Published in the Journal of Nutrition, the Rotterdam Study10 (a prospective cohort study of over 4,800 Dutch men and women) demonstrated that, compared to low vitamin K2 intake (less than 21.6 mcg per day), high intake (greater than 32.7 mcg per day) was associated with a: The clinical trial evidence11 for vitamin K’s effect on cardiovascular disease is small but growing. While the results are mixed, that’s partially because the study designs are mixed too. Some clinical trials support vitamin K’s beneficial role in combating calcification and atherosclerosis; others do not. Future, well-designed clinical evidence will be valuable to further inform the vitamin K/heart health relationship. While there’s no scientific consensus on the amount of vitamin K2 you need, doses at or around 100 mcg are found in supplements. And, a little vitamin K2 likely goes a long way. The Prospect-EPIC cohort study13 of over 16,000 Dutch women found that consuming 10 mcg per day of additional vitamin K2 was associated with a 9% reduction in coronary heart disease risk. This is not a causal finding, but informative nonetheless. Remember that your daily needs for vitamin K are 90 to 120 mcg depending on your gender. To put this recommendation in perspective, one-half cup of collard greens will deliver over 500 mcg of vitamin K1, and three ounces of nattō pack a vitamin K2 punch at 850 mcg. Supplements can deliver a range of vitamin K1 and K2 doses on top of what you consume from your diet. While safety is excellent for vitamin K214 (and K1), it’s always prudent to discuss any major diet or supplement changes with your doctor, especially if you have a health condition or are taking any medications. Anticoagulants and vitamin K are a well known drug-nutrient interaction. For this reason, some patients on anticoagulants think they should limit all sources of vitamin K. This is an unfortunate mistake that can create a vitamin K gap or deficiency. When taking blood-thinning medications, the important thing is to keep vitamin K inputs stable (not low). If a patient on blood thinners wants to incorporate vitamin K-dense foods (healthy foods!) into their diet or take a supplement containing vitamin K1 or K2, they should tell their doctor first. The healthcare practitioner will monitor key blood clotting biomarkers and adjust the medication accordingly. Remember, vitamin K2 is essentially the “usher” that directs calcium to all the right places (bones) while avoiding the wrong places like our arteries (heart). Supporting a healthy gut microbiome, consuming menaquinone-rich foods, and incorporating a vitamin K supplement (look for the K2 menaquinone form) are three practical ways to ensure you’re including this important form of vitamin K into your life. In addition to her mindbodygreen contributions, Ferira is published in Health, Metagenics Institute, American Family Physician, The Journal of Clinical Endocrinology & Metabolism, and Osteoporosis International. She has a passion for the translation of evidence-based science into innovative and high-quality products and information that help people lead healthier lives. She is a believer in compassionate, informed, and personalized approaches to nutrition, health care, and wellness. Ashley lives in beautiful Charleston, South Carolina, where she was born and raised. Whether savoring an orchestral performance or delectable meal at a local restaurant, you will find her enjoying Charleston’s cultural and culinary arts with family and friends.
