Vitamin K2 & Heart Health: Foods, Benefits, And Dosage

Vitamin K2 is a unique form of an essential micronutrient that plays an important role in heart health. Found in animal foods and fermented foods, vitamin K2 is often confused with vitamin K1 (which is found in plant foods) or overlooked altogether.

Vitamin K is a fat-soluble nutrient that naturally exists in two forms: K1 and K2. Vitamin K1 is known as phylloquinone, while vitamin K2 is referred to as menaquinone.

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.

An additional and fascinating source of vitamin K2 comes from bacterial synthesis in our gut. The exact vitamin K2 contribution from our gut microbiota is challenging to quantify, and the amount produced varies from person to person. Nonetheless, having a healthy gut supports the synthesis of vitamin K2.

If you've ever heard of a coronary artery calcium (CAC) score1, this test checks for calcium buildup in the walls of your coronary arteries. A higher score means you have more plaque and are at a higher risk of a cardiovascular event from heart disease. While the process of atherosclerosis is complex—involving endothelial dysfunction, elevated ApoB-containing lipoproteins, oxidation, inflammation, and autoimmune dysregulation—one major feature of advanced plaque is vascular calcification.

Calcified 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.” 

How does vitamin K accomplish this? It activates important proteins like matrix GLA protein (MGP). In fact, MGP is dependent on vitamin K for its functions, and this protein keeps calcium from depositing into blood vessels and other soft tissues. Supporting this mechanism, several observational studies have linked higher vitamin K2 intake with lower coronary calcification.

Interestingly, no such heart health findings were observed for vitamin K1 intake. 

A truly underappreciated nutrient gap, nationally representative data demonstrates that intake of vitamin K has room for improvement, with 70% of Americans over the age of two not meeting their daily vitamin K needs6.

No scientific consensus nor dietary recommendations exist for vitamin K2 (yet). As more research builds7, a recommendation specific to menaquinone vitamin K sources may be warranted in the future.

While classic vitamin K deficiency is rare in the average adult, it can occur. The result is abnormal bleeding9 caused by impaired blood clotting. Possible symptoms to look out for and report to your doctor include bruising, nosebleeds, bleeding gums, bloody urine or stools, and very heavy menstrual bleeding. 

While not full-on deficiency, vitamin K insufficiency can occur when people fail to consume adequate vitamin K over time. Blood clotting may remain normal, since there’s enough vitamin K to conserve that vital function. But, more subtle and potentially serious consequences can occur.

Whether in a multivitamin or standalone product, vitamin K2 supplements typically deliver menaquinones (MK) as MK-4 or MK-7 individually or in combination. Both are useful ways to augment the menaquinones that your diet and gut microbiome are providing. MK-7 may have better bioavailability12 than MK-4, but more studies should suss out this potential difference.

Vitamin K has an excellent safety profile, even at high doses. In fact, the National Academies Food and Nutrition Board did not even designate an upper limit for vitamin K1 or K2. That’s because no adverse effects14 have been documented from either form of vitamin K in humans or animal models when consumed via food or supplements.

Remember that your daily needs for vitamin K are 90 to 120 micrograms, depending on your gender. To put this recommendation in perspective, one-half cup of collard greens will deliver over 500 micrograms of vitamin K1, and three ounces of nattō pack a vitamin K2 punch at 850 micrograms. 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 (such as Warfarin) have a known drug-nutrient interaction with vitamin K1. 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. Direct oral anticoagulants (DOACs) do not have drug-nutrient interactions with vitamin K.

Vitamin K is a common nutrient gap and essential fat-soluble vitamin that comes in two varieties: vitamin K1 and K2. While both forms of this micronutrient support normal blood clotting and improve bone health, it’s time to pay more attention to vitamin K2 when it comes to our heart health.