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,

 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 Jess:

Can you recommend a good vitamin K2 supplement?

Our Adio 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.

References

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  33. 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.
  34. 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.
  35. 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.
  36. 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.