Understanding Vitamin K2 and Its Health Benefits
Medically reviewed by Allison Herries, RDNMedically reviewed by Allison Herries, RDNVitamin K2 (menaquinones), a form of vitamin K, is found in some animal-based foods or fermented foods. It is mainly made from the bacteria in the gut. You can also get vitamin K2 through supplementation.Vitamin K is a fat-soluble vitamin that is essential for certain functions in the body, such as blood clotting and bone formation. There are two main forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinones). Vitamin K2 is further broken down into different subtypes, such as MK-4 and MK-7.
TakeawayIn the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it does for prescription drugs. This means some supplement products may not contain what the label says. When choosing a supplement, look for third-party-tested products and consult a healthcare provider, registered dietitian nutritionist (RDN or RD), or pharmacist.
Getty Images / Ladanifer' title='Close-up of a person's hands using chopsticks to eat natto fermented soy beans from a small black bowl'>
Getty Images / Ladanifer
Vitamin K2 Supports Blood ClottingVitamin K is needed to make certain proteins, which are called clotting factors. Without vitamin K, the liver could not produce these clotting factors, resulting in bleeding.Newborns are given vitamin K after birth since the transport of vitamin K through the placenta is poor. Vitamin K deficiency bleeding can occur if vitamin K is not given. The American Academy of Pediatrics recommends a 0.5–1 milligram (mg) dose given intramuscularly (into the muscle) just once to prevent bleeding.People taking anticoagulant medications prescribed by their healthcare provider will need blood tests to monitor prothrombin levels (a clotting protein). When prothrombin levels are low, vitamin K may be prescribed to prevent bleeding. Sometimes, a vitamin K injection may be given to counteract the effects of a too-high dose of the blood-thinner warfarin.Vitamin K2 May Protect Bone HealthVitamin K is needed to form several proteins, including osteocalcin, one of the main proteins found in bone.Research on vitamin K and bone health has focused on the prevention and possible treatment of osteoporosis. Osteoporosis is a disorder that leads to weaker bones due to a loss of bone mass and bone mineral density and an increased risk of fractures.A meta-analysis of 16 studies in 6,245 postmenopausal women suggested that vitamin K2 supplementation positively affected bone mineralization and strength.Another recent meta-analysis reviewed studies that included supplementation with vitamin K for at least six months. The analysis concluded that vitamin K can reduce general fracture risk, but further studies are needed to establish the value of vitamin K in osteoporosis treatment.However, some randomized clinical studies have not found vitamin K to affect bone mineral density. Although vitamin K has a role in bone health, it remains unclear if supplemental vitamin K should be used to prevent or treat osteoporosis.
Should I Take Vitamin K2 and Vitamin D3 Together?Some have suggested that taking vitamin K and D together could enhance the effects of increasing bone mass. However, there isn't enough research to support the routine use of vitamin D3 and vitamin K2 combined.Additionally, there is some concern that this could lead to long-term soft tissue calcification and heart disease due to excess vitamin D.
Vitamin K2 May Improve Heart HealthThe role that vitamin K plays in heart health remains unclear. A protein called Matrix Gla-protein (MGP) works to prevent artery calcification, and this protein is dependent on vitamin K to do its job.In theory, inadequate vitamin K could cause MGP to be less productive, leading to greater artery calcification (calcium deposits). However, research has been mixed on the effectiveness of vitamin K for heart disease prevention.One meta-analysis of 21 studies involving over 200,000 people showed that vitamin K was associated with a moderately lower risk of coronary heart disease but not mortality. Another review showed that high vitamin K2 intake was associated with reduced coronary artery calcification and heart disease risk.However, in other studies, supplementing vitamin K has not consistently been shown to reduce calcification or atherosclerosis (plaque buildup) in the arteries.Additionally, a meta-analysis from 2024 found that vitamin K supplementation did not affect cardiovascular risk measures like weight, C-reactive protein (CRP), lipid profiles, or glucose (sugar) metabolism.The benefits of vitamin K2 supplementation for heart health are unclear. More research is needed to determine whether there is a place for vitamin K2 to help prevent heart disease.
Vitamin K1 vs. Vitamin K2Vitamin K1 and vitamin K2 are both forms of vitamin K, an essential nutrient. Vitamin K2 differs from vitamin K1 in how it is absorbed and its main sources.Vitamin K1 makes up most of the vitamin K you'll get from your diet. Vitamin K2, however, is naturally produced by gut bacteria in the body. You'll also get some through animal products and fermented foods.Vitamin K2 is also considered to have a higher absorption rate and lasts longer in the blood than vitamin K1, remaining in the blood for several days. This is believed to be because vitamin K2 is primarily found in animal-based foods, which contain fat that may lead to higher absorption.Vitamin K1, on the other hand, is mainly found in leafy green vegetables and fruits.
How to Get EnoughMost people get enough vitamin K through their diet by eating various foods. Vitamin K deficiency is rare. Most healthy people do not need to take supplements routinely.The Food and Nutrition Board of the Institute of Medicine has set adequate intakes (AIs) for vitamin K. For adults, the AI for vitamin K is 90 micrograms (mcg) for women and 120 mcg for men.Food sources will differ from vitamin K2 to vitamin K1. It's important to know that vitamin K1 is the main form of vitamin K you'll get from your diet. You'll get this form of vitamin K in leafy green vegetables, such as kale, and fruits like avocado and kiwi. While you'll get some vitamin K2 from food, it is also naturally produced by the bacteria in your gut.Food SourcesThe following are sources of vitamin K2 measured in micrograms (mcg) per 100 grams (g) of the food.Animal-based foods containing vitamin K2 include:Chicken (10.1 mcg)Pork liver (1.8 mcg)Pork meat (1.4 mcg)Beef (1.9 mcg)Salmon (0.6 mcg)Cheese (varies by type)It is also found in fermented foods, such as:Natto (108.9 mcg)Sauerkraut (5.5 mcg)
ExplainerNatto, a Japanese dish, is the richest source of vitamin K2, particularly MK-7. It is made by the fermentation of soybeans with a type of bacteria called Bacillus natto.
SupplementsVitamin K is available as a standalone nutrient or, more commonly, in multivitamin preparations. It may also be included in a fat-soluble vitamin solution (which includes vitamins A, D, E, and K) or in preparations marketed for bone health (which includes calcium, magnesium, and vitamin D).Vitamin K supplements come in vitamin K1 (phylloquinone or phytonadione) or vitamin K2 (MK-4 or MK-7).People with malabsorption disorders may need vitamin K supplementation if they cannot absorb sufficient amounts of vitamin K. This may include people with celiac disease, cystic fibrosis, short bowel syndrome, or ulcerative colitis.
ExplainerFor disease prevention, it is best to get these nutrients from the diet. Supplementing may be helpful for those at risk of bone fractures if they have low levels of vitamins or are unable to get enough through their diet, but it should always be discussed with a healthcare provider.
Is Vitamin K2 Safe to Take?Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your needs. Vitamin K2 is generally considered safe for most healthy people. The amounts found in multivitamin preparations are typically less than 100% of the daily value (DV), but doses can vary in other supplement blends.No upper limits have been established for vitamin K. According to the Food and Nutrition Board, a U.S. agency that studies issues of food safety and adequacy, no negative effects from vitamin K intake from food or supplements have been reported.For people prescribed anticoagulant (blood-thinning) medications, such as warfarin, vitamin K intake should be discussed with their primary care provider. It is important to keep your vitamin K intake consistent each day on these medications, as adding a supplement could make them less effective.Drug InteractionsReview your supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.Vitamin K can interact with a few medications:Jantoven (warfarin): Because warfarin is a blood thinner, vitamin K, which has a role in blood clotting, can make warfarin less effective. People newly prescribed this medication should be advised to keep their vitamin K intake consistent. Large variations in vitamin K intake could increase or decrease warfarin's anticoagulant effect.Antibiotics: Antibiotics can destroy the gut bacteria responsible for producing vitamin K. Supplements are not typically needed unless antibiotics are used for several weeks.Bile acid sequestrants: Bile acid sequestrants are often used to reduce cholesterol levels. They can also reduce the absorption of vitamin K. While taking them, it is recommended that vitamin K status be monitored.Xenical, Ali (orlistat): Orlistat is a medication used to treat obesity. It reduces the body's ability to absorb fat, resulting in weight loss. As a result, it may reduce the absorption of fat-soluble vitamins like vitamin K.SummaryVitamin K2 is available in animal-based foods and fermented foods. Both vitamin K1 and K2 contribute to your overall vitamin K status, and deficiency is rare.Vitamin K plays a role in blood clotting and bone health. There is some evidence that vitamin K2 supplementation may improve bone mineral density and prevent fractures. However, the evidence has not been enough for the FDA to issue a health claim for vitamin K and bone health.Before starting any supplement, discuss with your primary care provider whether supplementation would be of benefit to you. Read the original article on Verywell Health.
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