Vitamin K2, or menaquinone (MK), is a type of vitamin K. Vitamin K is a set of compounds that the body needs to function. Type K2 can benefit bone, blood and heart health.
Vitamin K2 occurs naturally in certain animal products and fermented foods, but most forms of vitamin K2 are produced naturally by bacteria in the human gut. Supplements are also available to increase vitamin K2 levels.
There are 10 types of vitamin K2, ranging from MK-4 to MK-13. Vitamin K2 subtypes MK-4, MK-7, and MK-9 are the most popular and well-studied.
Most people get enough vitamin K through their diet, but your healthcare provider may recommend that you take a vitamin K2 supplement if you don’t make enough vitamin K2 or eat enough foods that contain the vitamin.
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Vitamin K2 has been shown to potentially support bone health. The vitamin helps create three substances crucial for bone health: carboxylase, osteocalcin and matrix Gla protein (MGP).
Carboxylase is an enzyme needed to make proteins involved in bone growth and health. Osteocalcin and MGP bind to calcium to help build strong bones and reduce the risk of bone fractures.
Research has shown that vitamin K2 is particularly beneficial for the overall bone health of people with osteoporosis. With long-term treatment (longer than two years), vitamin K2 can help reduce the number of bone fractures experienced while helping to maintain overall bone strength (bone mineral density).
Vitamin K2 plays a role in preventing hardening of the blood vessels (calcification) by removing calcium from the blood vessels. When calcium builds up in a blood vessel, the vessel hardens, making it difficult for blood to flow through the body.
Calcification of blood vessels can lead to serious health conditions, such as high blood pressure (hypertension) and kidney disease, as well as death from coronary artery disease (CAD). And so, getting enough vitamin K2 can help prevent these conditions.
Vitamin K2 can support the body’s ability to clot blood. Again, vitamin K2 helps create the carboxylase enzyme. Carboxylase plays a major role in blood clotting.
Normal blood clotting is important—if your blood doesn’t clot properly (or is too thin), you may be at risk of excessive bleeding or bruising. If your blood clots too easily (or is too thick), blood will not flow properly through your body. In turn, you may be at risk of serious health problems such as stroke, heart attack, organ damage, or even death.
Getting enough vitamin K2 means you can create the right amount of the carboxylase enzyme, giving your body what it needs for blood clotting.
Vitamin K2 may play a role in cancer prevention. Some studies have found that vitamin K2 can block the growth of cancer cells, especially liver, lung, and pancreatic cancer cells. Meanwhile, other research shows that vitamin K2 may reduce the risk of death from cancer, but not the actual diagnosis of cancer.
Overall, more studies are needed to confirm whether – and how – vitamin K2 can protect against cancer.
Vitamin K2 can be found in a variety of animal and fermented foods.
Examples of animal products that contain vitamin K2 include:
- Chicken (chicken breast, chicken liver)
- Beef (ground beef, beef liver)
- Ham
- Salmon
- Shrimp
- Eel
- Hard cheeses (gouda, cheddar)
- Soft cheeses (blue cheese)
- Eggs (yolks, hard-boiled eggs)
Fermented foods are foods made from microorganisms such as bacteria and yeast. Microorganisms, which can exist naturally in food or be added, break down ingredients like sugar and turn them into other products, like gases. Fermented foods that contain vitamin K2 include natto (a Japanese food made from fermented soybeans) and sauerkraut.
Mixed nuts can also be a good source of vitamin K2.
Vitamin K deficiency (including vitamin K2) is rare in the United States because most people get enough vitamin K through their diet. However, some populations, including people who are unable to properly absorb the vitamin in their gastrointestinal (GI) tract, may require supplementation.
Vitamin K2 may be included in a multivitamin or combination product (often with calcium, magnesium, vitamin D, or other subtypes of vitamin K). The amount of vitamin K2 in the supplement depends on the product. However, most products typically have less than 75% of the recommended daily value.
Vitamin K2 supplements may also be available as a single product, usually with only one subtype of vitamin K2 (such as MK-4 or MK-7).
Dosage
Your dose of vitamin K2 depends on factors such as your age, gender and diet, as well as any medical conditions you may have.
The National Institutes of Health (NIH) and the Food and Nutrition Board have set daily recommended amounts of vitamin K. These recommendations are based on all types of vitamin K, not specifically on vitamin K2.
The recommended daily intake of vitamin K is 120 micrograms (mcg) for adult men and 90 mcg for adult women, including those who are pregnant or breastfeeding.
The amount of vitamin K2 in the supplement depends on the product. Most vitamin K2 products are available as capsules or softgels, which are taken by mouth. The recommended dose may depend on the product used.
For example, vitamin K2 subtype MK-7 is available as a supplement. The recommended dosage is usually between 50-120 mcg per day, but can range from 5-600 mcg. Doses of MK-7 between 180-360 mcg per day have shown benefits for heart health.
Talk to your doctor or pharmacist about what type of vitamin K2 supplement and dosage may be best for you.
Vitamin K2 is considered safe. No toxicity was reported in studies with vitamin K2. Doses of vitamin K2 up to 45 milligrams (45,000 mcg) have been used safely in studies for up to two years.
Potential drug interactions
Vitamin K2 can interact with medications you are already taking. Examples of drugs that may interact with vitamin K2 include:
- warfarin: This blood thinner (brand names include Jantoven and Coumadin) reverses the activity of all types of vitamin K, including vitamin K2 — especially the blood’s clotting ability. Any sudden changes in vitamin K intake can increase or decrease the blood-clotting effects of warfarin. This means that your blood can become thicker or thinner, which can cause serious health problems.
- antibiotics: These drugs can change the gut bacteria that make vitamin K2, potentially reducing the level of vitamin K2 in your body. This interaction is most noticeable with a group of antibiotics called cephalosporins, which include Keflex (cephalexin) and Omnicef (cefdinir). If you have been taking antibiotics for more than 10 days and have low vitamin K2 intake, your healthcare provider may recommend a vitamin K2 supplement.
- Bile acid sequestrants: Bile acid sequestrants are a class of drugs used to lower cholesterol levels. Examples of bile acid sequestrant medications include Prevalite (cholestyramine), Colestid (colestipol), and Velchol (colesevelam). These drugs can reduce your body’s absorption of vitamin K2.
- orlistat: Available over the counter (Alli) or with a prescription (Xenical), Orlistat is a drug used for weight loss. Orlistat can reduce the absorption of vitamin K2 in your body.
What to look for
Unlike prescription and over-the-counter (OTC) drugs, supplements such as vitamin K2 are not regulated by the US Food and Drug Administration (FDA). Therefore, purchasing vitamin K2 products that have been tested by independent third-party organizations helps to ensure that the listed ingredients are actually the ingredients of the supplement.
Popular organizations that offer quality testing include the United States Pharmacopoeia (USP), NSF International, and ConsumerLab.com. You can look for their labels on the product packaging.
Can You Take Too Much Vitamin K2?
Vitamin K2 has not been shown to cause harm or toxicity. Therefore, the NIH and the Food and Nutrition Board have not established a maximum upper level or dose of vitamin K2. Taking high doses of vitamin K2 is unlikely to cause adverse health effects.
Vitamin K2 has minimal side effects. The most common side effects reported are gastrointestinal problems such as diarrhea, nausea, or upset stomach.
Skin rashes have also been reported with vitamin K2 and should improve after stopping the supplement.
Vitamin K2, or menaquinone, is a type of vitamin K that is produced in your intestines and is available in certain foods. Vitamin K2 is beneficial for bone health as well as overall blood and heart health. If your body doesn’t make enough vitamin K2 or you can’t get enough of the vitamin from your diet, your healthcare provider may recommend that you take a vitamin K2 supplement.
If you are interested in taking a vitamin K2 supplement, talk to your doctor about whether a supplement would benefit you. They can discuss dosage, safety concerns, and side effects.