Dr Jess says: You may never have heard of it, but did you know that vitamin K2 is probably one of the most important vitamins? It can help to treat a wide range of conditions and is at its optimal best, when taken alongside vitamin D (and if you are taking vitamin D, you should consider adding K2).
Fermented foods, especially kefir, are great natural sources of K2, while some of the more obscure vitamin K2-rich foods, like natto, are more of an acquired taste!
Any patient with bone concerns, cancer or heart problems should definitely consider supplementing with vitamin K2. I have seen it significantly improve osteoporosis on scans where vitamin D and calcium supplements have failed.
Vitamin K2 is a recently discovered, wonderful nutrient that has a huge range of health benefits. We are starting to understand that many common prescription drugs can make you more likely to become deficient in K2, which is why if you have any unresolved health concerns, adding a K2 supplement may be the missing piece of the puzzle.
vitamin K2 is a vital nutrient that is often lacking in a modern diet
Vitamin K is a fat-soluble vitamin that has two natural forms: K1 and K2. Vitamin K1 is commonly found in green, leafy vegetables. Vitamin K2 is found in fermented foods and in low levels in animal products. Vitamin K1 can be converted to vitamin K2 in the bowel, but we can struggle to absorb and break down vitamin K1.
Vitamin K2 has several different subtypes (MK4-MK15). One of the most important is MK-7, which is found in high levels in natto (a fermented Japanese bean) and is shown to be very good for our health.
Vitamin K has a critical role, working in our liver to produce substances that help our blood clot. A deficiency can cause bleeding and bruising. However, we also know that vitamin K has a wide range of roles outside of the liver, particularly in our bones and blood vessels. Foods that are rich in vitamin K2 and supplements of K2 (MK-7) have been shown to be far more effective at maintaining vitamin K levels than vitamin K1.1
Higher levels of vitamin K in the diet were shown to reduce the risk of dying from heart disease and stroke, cancer or from any cause.2
many medications, including antibiotics, can make us deficient in vitamin K2
The use of antibiotics, phenytoin (a seizure medication), low-fat diets, orlistat (a weight loss medication) and other fat loss medications, oestrogen-based drugs, including the combined contraceptive pill and HRT all reduce our natural levels of vitamin K.3 Patients with inflammatory bowel disease (Crohn’s or ulcerative colitis) or coeliac disease are at particularly high risk of being low in vitamin K (and also vitamin D).4
vitamin K is very safe to take
The recommended daily dose is likely much lower than the amount for optimum health.5 While caution with vitamin K is advised if taking warfarin or other medications to reduce blood clotting, otherwise vitamin K supplements have been used safely in numerous clinical trials, including during pregnancy.6 Consult your healthcare provider if you are unsure whether taking a vitamin K supplement is appropriate. If you do decide to take a supplement, make sure to choose one that contains vitamin K2 in the MK-7 form, which is shown to be most effective.
vitamin K2 deficiency can cause heart problems and high blood pressure
Vitamin K supplements help our blood vessels to stay healthier and more elastic, which reduces our risk of high blood pressure and heart problems.7 A higher intake of vitamin K2 (not K1), reduced the risk of peripheral vascular disease (the blocking of the arteries ) in a patient study.8 Several proteins that are affected by vitamin K levels, keep our heart and blood vessels healthy.9
vitamin K can affect our blood sugar
Vitamin K supplements can help our bodies to better deal with sugar and keep our insulin levels more stable, helping to lower the risk of type 2 diabetes.10 In animal studies, decreasing levels of vitamin K in the diet was shown to affect their ability to regulate blood sugar.11
vitamin K2 deficiency can cause problems with our teeth, and increase our risk of dental cavities
Vitamin K2 is necessary for the proper development of the mouth and teeth. Low levels of vitamin K and D can lead to the overcrowding of our teeth and issues with the jaw.12 Vitamin K likely helps to reduce the risk of dental cavities, affecting saliva and the bacterial balance in the mouth.13
vitamin K2 supplements can help improve and prevent hardening of the arteries, reduce heart disease and prevent diabetes
Vitamin K2 is important in the regulation of calcium. A deficiency can cause calcification (hardening) of the artery walls, leading to heart and vascular disease.14 Vitamin K supplements (in MK-7 form) improved arterial stiffness (a sign of cardiovascular disease) in post-menopausal women who took supplements for three years.15
vitamin K2 has been shown to effectively reduce the risk of type 2 diabetes
(more effectively than vitamin K1), and appears to act on insulin levels and as an anti-inflammatory.16
it can be important to take vitamin K2 alongside vitamin D, for our bones and joints
Vitamin K2 regulates bone remodelling (the continual turnover of bone, with removal of old or damaged bone and the development of new bone), making it important for our bone health.17 A large review of post-menopausal women with osteoporosis showed that vitamin K2 helped to maintain bone mineral density and prevent fractures.18
vitamin K2 supplements should be considered in any patients with a higher risk of osteoporosis
(e.g. if you are taking steroids.)19 Vitamin K2 levels have also been shown to be lower, when examining the knees of patients with severe osteoarthritis, suggesting it has a role in protecting joints from damage.20
vitamin K2 (MK-7 form) has had promising results in patients suffering from rheumatoid arthritis,
When compared to standard therapies, improving blood markers of inflammation over three months.21
vitamin K2 may even reduce the risk of cancer
Vitamin K2 has been shown to have a positive effect on suppressing cancer cell growth in small studies in animals and on cancer cells, including breast cancer,22 bladder, prostate and liver cancer.23 Several vitamin K2 derivatives are being developed for use against cancer.24 Nearly 80% of advanced cancer patients were found to have mild to severe vitamin K deficiency in a recent study.25
other benefits of vitamin K
- Animal studies show that vitamin K2 supplements seem to improve anxiety and depression in rats, who were fed a high sugar diet,26 suggesting it may help to enhance our mood and balance our blood sugar.
- Excessive bleeding from heavy periods (menorrhagia), can be a sign of vitamin K deficiency.27
- Vitamin K can improve heart output during exercise, and therefore cardiovascular fitness in athletes. A small study showed that supplementation with vitamin K2 for eight weeks improved heart output by 12%.28
- Vitamin K2 has been shown to promote liver regeneration and recovery after cirrhosis and partial removal.29
- SIBO (Small Intestinal Bacterial Overgrowth) is often associated with an increased risk of atherosclerosis. This appears to be due to a deficiency in vitamin K2.30
- Vitamin K2 supplements may help reduce complications and hardening of the arteries in kidney dialysis patients.31 Most dialysis patients have a vitamin K deficiency, which can cause complications. Taking a supplement is advised.32
- Vitamin K2 supplements given to children with thalassemia major, a genetic condition, improved their bone density; one of the complications of the condition.33
- Myelodysplastic syndrome anaemia, which is a problem with the bone marrow, can be improved by vitamin K supplements.34
- Taking a vitamin K supplement through the late stage of pregnancy can avoid complications of vitamin K deficiency in the newborn baby.35 It’s particularly important for mothers to have good levels of vitamin K before they give birth, to avoid bleeding complications in the baby.
how do I get my vitamin K levels tested?
Most hospitals and GP practices don’t test for vitamin K levels. Instead, they do a PPT (Prolonged Prothrombin Time) test, measuring blood clotting, which is affected by severe vitamin K deficiency.
Arguably, there is a benefit to also supplementing vitamin K when PPT is unaffected, if vitamin K levels are in the lower range. A normal value is between 0.2-3.2 ng/mL, but symptoms have been seen at levels of 0.5 or under. Many independent private doctors and practitioners can offer a blood test for vitamin K.
how much vitamin K do I need?
The recommended daily amount of vitamin K1 is 90 – 120μg per day (there is no recommended level for K2). It’s also worth noting that vitamin K2 is a fat-soluble vitamin, meaning it cannot be absorbed without fat (so take a supplement with food). However, it is very safe at even much higher levels. 1000μg per day or less is considered to be safe for most people.36
the best natural sources of vitamin K1:
- Kale – 1 cup, cooked = 1062μg
- Spinach – 1 cup, cooked = 889μg
- Swiss Chard – 1 cup, cooked = 299μg
- Broccoli – 1 cup, cooked = 220μg
- Asparagus – 1 cup, cooked = 91μg
the best natural sources of vitamin K2:
- Natto – 800-1000μg per 100g
- Eggs (pasture-raised) – 32.1μg, per raw egg yolk
- Cheese (made from grass-fed milk). Gouda, blue cheese and Cheshire are ideal – 16-70μg per 100g
- Grass-fed butter – 15μg per 100g
- Grass-fed meat – 4.5-60μg per 100g
foods high in vitamin K2
Natto (fermented soybeans). Although soy can be an issue for some people, fermented soy is definitely a worthy superfood (and is why soy was originally thought to be healthy). You can buy natto (make sure it is made from non-GM modified soy) or make it (this is a bit tricky and requires organic soybeans and a natto culture; search online for recipes). In Japan, natto is often served with steamed rice. It’s definitely an acquired taste!
Fermented food like kefir and sauerkraut. Yet another reason fermented foods are amazing! They are a great natural source of vitamin K2. The amounts that they contain can be variable, but eating fermented foods has many other benefits.
Butter and cheese. Hard cheese, soft cheese, aged cheese and butter all are good sources of vitamin K2. Gouda and brie are good options, and by far the highest amount is found in dairy products that come from organically raised, grass-fed cows, in case you needed another reason to eat organic!
Egg yolk. Another wonderful reason to eat eggs! Organic, free-range hens use vitamin K1 in the grass, and convert it to vitamin K2, which is then imparted into our eggs.
Chicken and chicken liver. Chicken and chicken liver are both good sources of K2. If you’re not a fan of liver, there is always delicious pâté!
If you have serious digestive problems, including Crohn’s or coeliac, are taking long-term antibiotics or have leaky gut, consider increasing your vitamin K2 foods or taking a supplement (a combined vitamin D/K2 supplement is a great idea), as the gut bacteria help our synthesis of vitamin K. Vitamin K2 can also be more likely to be deficient in those taking statins, oral contraceptives, aspirin, orlistat or phenytoin.
q&a with Dr Jess:
Can you recommend a good vitamin K2 supplement?
Our one. multivitamin capsules contain MK7 K2, derived from natto, making it an easy way to ensure your daily needs are met. While a simple cup of leafy green vegetables each day can ensure your K1 needs are met, you’d need to eat a lot of butter or cheese to get your daily K2 quota! If you do want to ensure your K2 comes from food, try and eat some fermented food and pasture-fed meat and butter and some cheese each day.
- Schwalfenberg GK.Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health J Nutr Metab. 2017;2017:6254836. doi:10.1155/2017/6254836.
- Juanola-Falgarona M, Salas-Salvadó J, Martínez-González MÁ, Corella D, Estruch R, Ros E, Fitó M, Arós F, Gómez-Gracia E, Fiol M, Lapetra J, Basora J, Lamuela-Raventós RM, Serra-Majem L, Pintó X, Muñoz MÁ, Ruiz-Gutiérrez V, Fernández-Ballart J, Bulló M. Dietary intake of vitamin K is inversely associated with mortality risk J Nutr. 2014 May;144(5):743-50. doi: 10.3945/jn.113.187740. Epub 2014 Mar 19. Erratum in: J Nutr. 2016 Mar;146(3):653. PMID: 24647393.
- Schwalfenberg GK. Vitamins K1 and K2:Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health J Nutr Metab. 2017;2017:6254836. doi:10.1155/2017/6254836
- Kuwabara A, Tanaka K, Tsugawa N, Nakase H, Tsuji H, Shide K, Kamao M, Chiba T, Inagaki N, Okano T, Kido S.High prevalence of vitamin K and D deficiency and decreased BMD in inflammatory bowel disease Osteoporos Int. 2009 Jun;20(6):935-42. doi: 10.1007/s00198-008-0764-2. Epub 2008 Sep 30. PMID: 18825300.
- Theuwissen E, Magdeleyns EJ, Braam LA, Teunissen KJ, Knapen MH, Binnekamp IA, van Summeren MJ, Vermeer C.Vitamin K status in healthy volunteers Food Funct. 2014 Feb;5(2):229-34. doi: 10.1039/c3fo60464k. PMID: 24296867.
- Tsuchie H, Miyakoshi N, Hongo M, Kasukawa Y, Ishikawa Y, Shimada Y. Amelioration of pregnancy-associated osteoporosis after treatment with vitamin K₂: a report of four patients Ups J Med Sci. 2012 Aug;117(3):336-41. doi: 10.3109/03009734.2012.676573. Epub 2012 Jul 3. PMID: 22746299; PMCID: PMC3410294.
- Theuwissen E, Smit E, Vermeer C. The role of vitamin K in soft-tissue calcification Adv Nutr. 2012 Mar 1;3(2):166-73. doi: 10.3945/an.111.001628. PMID: 22516724; PMCID: PMC3648717.
- Vissers LET, Dalmeijer GW, Boer JMA, Verschuren WMM, van der Schouw YT, Beulens JWJ. The relationship between vitamin K and peripheral arterial disease 2016 Sep;252:15-20. doi: 10.1016/j.atherosclerosis.2016.07.915. Epub 2016 Jul 25. PMID: 27494446.
- Wen L, Chen J, Duan L, Li S. V. Vitamin K‑dependent proteins involved in bone and cardiovascular health (Review) Mol Med Rep. 2018 Jul;18(1):3-15. doi: 10.3892/mmr.2018.8940. Epub 2018 Apr 27. PMID: 29749440; PMCID: PMC6059683.
- Manna P, Kalita J. Beneficial role of vitamin K supplementation on insulin sensitivity, glucose metabolism, and the reduced risk of type 2 diabetes: A review Nutrition. 2016 Jul-Aug;32(7-8):732-9. doi: 10.1016/j.nut.2016.01.011. Epub 2016 Jan 25. PMID: 27133809.
- Sakamoto N, Wakabayashi I, Sakamoto K. Low vitamin K intake effects on glucose tolerance in rats Int J Vitam Nutr Res. 1999 Jan;69(1):27-31. doi: 10.1024/0300-9818.104.22.168. PMID: 10052018.
- Tyszkowski M. Is There a Relationship between Nutrition, Facial Development, and Crowding of the Teeth? Int J Orthod Milwaukee. 2016 Spring;27(1):15-7. PMID: 27319035.
- Southward K. A hypothetical role for vitamin K2 in the endocrine and exocrine aspects of dental caries Med Hypotheses. 2015 Mar;84(3):276-80. doi: 10.1016/j.mehy.2015.01.011. Epub 2015 Jan 19. PMID: 25636605.
- Flore R, Ponziani FR, Di Rienzo TA, Zocco MA, Flex A, Gerardino L, Lupascu A, Santoro L, Santoliquido A, Di Stasio E, Chierici E, Lanti A, Tondi P, Gasbarrini A. Something more to say about calcium homeostasis: the role of vitamin K2 in vascular calcification and osteoporosis Eur Rev Med Pharmacol Sci. 2013 Sep;17(18):2433-40. PMID: 24089220.
- Knapen MH, Braam LA, Drummen NE, Bekers O, Hoeks AP, Vermeer C. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial Thromb Haemost. 2015 May;113(5):1135-44. doi: 10.1160/TH14-08-0675. Epub 2015 Feb 19. PMID: 25694037.
- Li Y, Chen JP, Duan L, Li S. Effect of vitamin K2 on type 2 diabetes mellitus: A review Diabetes Res Clin Pract. 2018 Feb;136:39-51. doi: 10.1016/j.diabres.2017.11.020. Epub 2017 Dec 2. PMID: 29196151.
- Myneni VD, Mezey E. Regulation of bone remodeling by vitamin K2 Oral Dis. 2017 Nov;23(8):1021-1028. doi: 10.1111/odi.12624. Epub 2017 Apr 5. PMID: 27976475; PMCID: PMC5471136.
- Huang ZB, Wan SL, Lu YJ, Ning L, Liu C, Fan SW. Does vitamin K2 play a role in the prevention and treatment of osteoporosis for postmenopausal women: a meta-analysis of randomized controlled trials Osteoporos Int. 2015 Mar;26(3):1175-86. doi: 10.1007/s00198-014-2989-6. Epub 2014 Dec 17. PMID: 25516361.
- Prabhoo R, Prabhoo TR. Vitamin K2: a novel therapy for osteoporosis J Indian Med Assoc. 2010 Apr;108(4):253-4, 256-8. PMID: 21114195.
- Ishii Y, Noguchi H, Takeda M, Sato J, Yamamoto N, Wakabayashi H, Kanda J, Toyabe S. Distribution of vitamin K2 in subchondral bone in osteoarthritic knee joints Knee Surg Sports Traumatol Arthrosc. 2013 Aug;21(8):1813-8. doi: 10.1007/s00167-012-2239-4. Epub 2012 Oct 16. PMID: 23070274.
- Abdel-Rahman MS, Alkady EA, Ahmed S. Menaquinone-7 as a novel pharmacological therapy in the treatment of rheumatoid arthritis: A clinical study Eur J Pharmacol. 2015 Aug 15;761:273-8. doi: 10.1016/j.ejphar.2015.06.014. Epub 2015 Jun 11. PMID: 26073022.
- Kiely M, Hodgins SJ, Merrigan BA, Tormey S, Kiely PA, O’Connor EM. Real-time cell analysis of the inhibitory effect of vitamin K2 on adhesion and proliferation of breast cancer cells Nutr Res. 2015 Aug;35(8):736-43. doi: 10.1016/j.nutres.2015.05.014. Epub 2015 May 30. PMID: 26082424.
- VAzuma K, Urano T, Ouchi Y, Inoue S. Vitamin K2 suppresses proliferation and motility of hepatocellular carcinoma cells by activating steroid and xenobiotic receptor Endocr J. 2009;56(7):843-9. doi: 10.1507/endocrj.k09e-108. Epub 2009 Jun 24. PMID: 19550077.
- Amalia H, Sasaki R, Suzuki Y, Demizu Y, Bito T, Nishimura H, Okamoto Y, Yoshida K, Miyawaki D, Kawabe T, Mizushina Y, Sugimura K. Vitamin K2-derived compounds induce growth inhibition in radioresistant cancer cells Kobe J Med Sci. 2010 Sep 28;56(2):E38-49. PMID: 21063145.
- Harrington DJ, Western H, Seton-Jones C, Rangarajan S, Beynon T, Shearer MJ. A study of the prevalence of vitamin K deficiency in patients with cancer referred to a hospital palliative care team and its association with abnormal haemostasis J Clin Pathol. 2008 Apr;61(4):537-40. doi: 10.1136/jcp.2007.052498. Epub 2007 Oct 8. PMID: 17923470.
- Gancheva SM, Zhelyazkova-Savova MD. Vitamin K2 Improves Anxiety and Depression but not Cognition in Rats with Metabolic Syndrome: a Role of Blood Glucose? Folia Med (Plovdiv). 2016 Dec 1;58(4):264-272. doi: 10.1515/folmed-2016-0032. PMID: 28068285.
- Zekavat OR, Fathpour G, Haghpanah S, Dehghani SJ, Zekavat M, Shakibazad N. Acquired Vitamin K Deficiency as Unusual Cause of Bleeding Tendency in Adults: A Case Report of a Nonhospitalized Student Presenting with Severe Menorrhagia. Case Rep Obstet Gynecol. 2017;2017:4239148. doi: 10.1155/2017/4239148. Epub 2017 Aug 27. PMID: 28928999; PMCID: PMC5592002.
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- Lin M, Sun P, Zhang G, Xu X, Liu G, Miao H, Yang Y, Xu H, Zhang L, Wu P, Li M. PMID: 24236453.Vitamin K2-enhanced liver regeneration is associated with oval cell expansion and up-regulation of matrilin-2 expression in 2-AAF/PH rat model Curr Mol Med. 2014 Mar;14(3):361-9. doi: 10.2174/1566524013666131118113017.
- Ponziani FR, Pompili M, Di Stasio E, Zocco MA, Gasbarrini A, Flore R. Subclinical atherosclerosis is linked to small intestinal bacterial overgrowth via vitamin K2-dependent mechanisms World J Gastroenterol. 2017 Feb 21;23(7):1241-1249. doi: 10.3748/wjg.v23.i7.1241. PMID: 28275304; PMCID: PMC5323449.
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- Ozdemir MA, Yilmaz K, Abdulrezzak U, Muhtaroglu S, Patiroglu T, Karakukcu M, Unal E. The efficacy of vitamin K2 and calcitriol combination on thalassemic osteopathy J Pediatr Hematol Oncol. 2013 Nov;35(8):623-7. doi: 10.1097/MPH.0000000000000040. PMID: 24136015.
- Takami A, Asakura H, Nakao S. Menatetrenone, a vitamin K2 analog, ameliorates cytopenia in patients with refractory anemia of myelodysplastic syndrome Ann Hematol. 2002 Jan;81(1):16-9. doi: 10.1007/s00277-001-0391-x. Epub 2001 Dec 8. PMID: 11807630.
- Nishiguchi T, Yamashita M, Maeda M, Matsuyama K, Kobayashi T, Kanayama N, Terao T. Improvement of vitamin K status of breastfeeding infants with maternal supplement of vitamin K2 (MK40) Semin Thromb Hemost. 2002 Dec;28(6):533-8. doi: 10.1055/s-2002-36697. PMID: 12536346.
- Marles RJ, Roe AL, Oketch-Rabah HA. US Pharmacopeial Convention safety evaluation of menaquinone-7, a form of vitamin K. Nutr Rev. 2017 Jul 1;75(7):553-578. doi: 10.1093/nutrit/nux022. PMID: 28838081.