Vitamin K2 belongs to the vitamin K family, an important class of nutrients involved in maintaining bone health and blood clotting. Naturally found in natto, egg yolks, butter, cheeses, and chicken, Vitamin K2 is synthesized by bacteria.
Some people take this vitamin as a supplement. Vitamin K2 is also called menaquinone. The two most common forms are MK-7 and MK-4. Studies show vitamin K2 might protect against various health problems, including osteoporosis and heart disease. Moreover, vitamin K2 is known to protect against certain types of cancer.
In addition to vitamin K2’s vital role in wound healing and blood clotting, vitamin K2 has many other health benefits. Following are some of the health benefits.
Preliminary studies show that vitamin K2 might help in the treatment of different types of cancer. For instance, in 2012, researchers found that the vitamin substantially improved survival among individuals with hepatocellular carcinoma.[iii] Nevertheless, a 2017 study showed that vitamin K2 intake wasn’t related to cancer mortality.[iv]
Some studies show that vitamin K2 might reduce the risks of osteoporosis and preserve bone strength as you age. In a 2006 report, researchers examined the effect of vitamin K1 and K2 on bone fractures and loss. Results show that supplementing vitamins k2 and k1 might reduce bone mass.
Also, vitamin K2 was found to play a significant role in the prevention of bone fractures. A more recent study found that combining biophosphate with vitamin K2 might help prevent bone fractures in women who are post-menopause with vitamin K2 deficiency and osteoporosis.[v]
A few studies show that vitamin K2 intake might help reduce risks of cardiovascular disease. In a study focusing on Nutrition, Metabolism, and Heart Diseases, researchers examined the dietary intake of vitamin k2 and vitamin k1 from a sample of 16,057 women and found that women who took high amounts of vitamin K2 have lower risks of cardiovascular disease. According to the scientists, the association was primarily because of the vitamin K2 types, MK-9, MK-8, and MK-7.[vi]
Also, a 2010 study shows that vitamin K2 might help protect against different cardio-metabolic disorders (like metabolic syndrome, type II diabetes, and heart disease).[vii]
Vitamin K2 Deficiency
In reference to the Office of Dietary Supplements (ODS), vitamin K2 deficiency is very rare in the United States. Infants and People with gastrointestinal diseases like ulcerative colitis and celiac disease are at a higher risk of vitamin K2 deficiency.
Severe deficiency of vitamin K2 increases the time taken for blood to clot, making an individual vulnerable to bleeding and bruising and considerably increasing the risks of hemorrhage.[i] Also, a deficiency of vitamin K2 might reduce bone mineralization that can lead to osteoporosis.
Vitamin K2 Deficiency Symptoms
The primary sign of vitamin K2 deficiency is excess bleeding. Remember, bleeding can also happen in other areas rather than a wound or cut site. The bleeding might also be apparent if a person:
- Produces dark black stool that contains some blood
- Bleeds in the mucous membranes
- Gets smaller blood clots
- Bruises easily
Among infants, doctors might observe vitamin K2 deficiency if:
- The brain starts bleeding suddenly
- Bleeding on the penis after the infant has been circumcised
- Bleeding in the gastrointestinal tract, nose, skin, and other areas
- Bleeding from an area where an umbilical cord has been removed
Infants are at higher risks of vitamin K2 deficiency for different reasons[ii] , like:
- Infants do not produce Vitamin K2 in the first days of life
- An infants liver does not use vitamin K2 efficiently
- Vitamin K2 doesn’t transfer properly from the mother’s placenta
- Breast milk low in vitamin K
Vitamin K2 Side Effects
Although no tolerable upper limit has so far been set for vitamin K2. Toxicity is rare and unlikely from consuming foods with vitamin K2.
Nonetheless, taking supplements could lead to toxicity. Vitamin K2 might interact with different medications, including weight-loss drugs, cholesterol-lowering drugs, antibiotics, anticonvulsants, and blood thinners.
Consult a health physician before you start taking vitamin K supplements. This is because it might interact with anticoagulants. So, if you’re taking anticoagulants like warfarin, you should not increase vitamin K2 intake without consulting a doctor.
Along with the required effects, vitamin K2 might also cause some undesired side effects.[viii] Even though not all the side effects might occur, incase they do, you may need urgent medical attention. Check with a health physician incase any of these side effects occur when taking vitamin K2.
- Muscle stiffness
- Yellow skin or eyes
- General body swelling
- Enlarged liver
- Difficulties breathing
- Decreased activity or movement
- Decreased appetite
Rare – only with Injections
- Troubled wheezing or breathing
- Chest tightness
- Swelling of lips, face, or eyelids
- Itching, hives, and/or skin rash
- Fainting or lightheadedness
- Irregular or fast breathing
- Low blood pressure
- Increased sweating
- Weak or fast heartbeat
- Flushing or blue color or skin redness
Some side effects of vitamin K2 might occur, which don’t require medical attention. The side effects might go away as your body adjusts to the supplements. Also, your doctor may be able to tell you about how you can prevent these side effects.
Vitamin K2 Dosage and preparation
The daily recommended dietary allowance for vitamin K1 in adults is 120 micrograms and 90 micrograms for men and women, respectively. However, no scientific RDA for vitamin K2 exists just yet. With more researchers working around the clock to figure this out, a suggestion on menaquinone might be needed in the future. Although vitamin K2 is fat-soluble, what you eat is quickly used, metabolized, and removed from the body.
Ways To Get Your Vitamin K2
Vitamin K2 is mainly found in animal products like cheese and pork. Also, it’s available in fermented foods such as pickled vegetables, pickles, sauerkraut, and natto. You can also get your vitamin K2 from supplements. However, we strongly recommend you prioritize getting your vitamin K2 RDA from foods because in doing so, you get more benefits, rather than just taking vitamin K2 supplements, which is just that, vitamin K2.
Foods Rich In Vitamin K2
Following are the best food sources you should consider adding to your diet to get enough vitamin K2.
- Kale: a cup of cooked kale contains 544 micrograms of vitamin K
- Brussels sprouts: a one-cup serving contains 285 mcg
- Broccoli: one-cup serving has 164 mcg
- Asparagus: one-cup serving has 80 mcg
- Cabbage: one cup of cabbage (cooked) has 118 mcg
- Green snap beans: a one-cup serving of green snap beans (cooked) has 60 mcg
- Kiwi: one-cup serving has 72.5 mcg
- Collard greens: one-cup serving has 609 mcg
- Spinach: a one-cup serving of spinach (cooked) has 1,020 mcg
- Turnip greens: one cup of turnip greens (cooked) has 531 mcg
As you can see, dark leafy green vegetables are some of the best food sources of vitamin K2. Other types of foods that are higher in vitamin K2 include vegetables like broccoli, asparagus, and fruits such as kiwi.
Because vitamin K2 is often associated with bone strength, heart health, and other benefits, it is highly recommended that you eat foods high in this essential nutrient. You should consider combining vitamin K2 foods with healthy fats to ensure maximum absorption. However, if you still can’t get enough vitamin K2, read on to learn more about vitamin K2 supplements.
Although the ODS report shows that vitamin K deficiency is pretty rare mainly because most people get enough vitamin K2 from their foods, any individual at risk might consider taking supplements. Most multivitamins contain vitamin K2. You can buy vitamin K as a standalone dietary supplement or along other nutrients like magnesium, calcium, or vitamin D.
Types of vitamin K available in supplements include:
- Vitamin K2 as either MK-7 or MK-4.
- Vitamin K1 as phytonadione or phylloquinone
The concentrations of vitamin K2 and vitamin K1 usually vary based on the supplements you’re taking. Remember to check the nutrition labels before buying supplements. Also, vitamin K might interact with some pharmaceutical medications; particularly thinners, therefore, it’s essential for individuals taking prescription drugs to talk to a physician before they start taking these dietary supplements.
What is the main benefit of vitamin K2?
What food is high in vitamin K2?
What veggies are high in vitamin K2?
Can vitamin K2 raise my blood pressure?
Should you take vitamin K2 with vitamin D3?
Is too much vitamin K2 harmful?
How much vitamin K2 do I need to take every day for osteoporosis?
- [i] Cockayne S, Adamson J, Lanham-new S, Shearer MJ, Gilbody S, Torgerson DJ. Vitamin K and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials. Arch Intern Med. 2006;166(12):1256-61. doi:10.1001/archinte.166.12.1256
- [ii] Koitaya N, Ezaki J, Nishimuta M, Yamauchi J, Hashizume E, Morishita K, Miyachi M, Sasaki S, Ishimi Y. Effect of Low Dose Vitamin K2 (MK-4) Supplementation on Bio-Indices in Postmenopausal Japanese Women. J Nutr Sci Vitaminol (Tokyo). 2009 Feb;55(1):15-21.
- [iii] Zhong JH, Li H, Li LQ, et al. Adjuvant therapy options following curative treatment of hepatocellular carcinoma: a systematic review of randomized trials. Eur J Surg Oncol. 2012;38(4):286-95. doi:10.1016/j.ejso.2012.01.006
- [iv] Zwakenberg SR, Den braver NR, Engelen AIP, et al. Vitamin K intake and all-cause and cause specific mortality. Clin Nutr. 2017;36(5):1294-1300. doi:10.1016/j.clnu.2016.08.017
- [v] Iwamoto J, Takeda T, Sato Y. Role of vitamin K2 in the treatment of postmenopausal osteoporosis. Curr Drug Saf. 2006;1(1):87-97. doi:10.2174/157488606775252629
- [vi] Gast GC, De roos NM, Sluijs I, et al. A high menaquinone intake reduces the incidence of coronary heart disease. Nutr Metab Cardiovasc Dis. 2009;19(7):504-10. doi:10.1016/j.numecd.2008.10.004
- [vii] Rees K, Guraewal S, Wong YL, et al. Is vitamin K consumption associated with cardio-metabolic disorders? A systematic review. Maturitas. 2010;67(2):121-8. doi:10.1016/j.maturitas.2010.05.006
- [viii] Gast GC, De roos NM, Sluijs I, et al. A high menaquinone intake reduces the incidence of coronary heart disease. Nutr Metab Cardiovasc Dis. 2009;19(7):504-10. doi:10.1016/j.numecd.2008.10.004