Dr Jess: Vitamin K2 is probably one of the most important and least well known vitamins. I advise my adult patients taking Vitamin D supplements to take Vitamin K2 as well.
Fermented foods, particularly kefir are also an important health food to add into our diets containing Vitamin K2 – although natto is definitely an acquired taste!
Any patient with bone concerns, cancer or heart problems should definitely consider Vitamin K2 and I have seen it significantly improve osteoporosis on scans where Vitamin D and Calcium supplements have failed.
Vitamin K2 is a recently discovered and wonderful nutrient that has a huge range of health benefits, and many common drugs can make you likely to become deficient. Learn more below…
Vitamin K is a fat-soluble vitamin that has two natural forms K1 and K2. Vitamin K1 is commonly found in green leafy vegetables and 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 breakdown K1. Vitamin K2 has several different subtypes (MK4-MK15) and 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 acting in our liver to produce substances that help our blood clot, and deficiency can cause bleeding and bruising. However, we also know it has a wide range of roles outside of the liver, particularly in our bones and blood vessels. Foods 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 Vitamin K levels 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
Use of antibiotics, phenytoin (a seizure medication), low fat diets, orlistat and fat loss medications, oestogen-based drugs like the combined contraceptive pill and HRT (3) all reduce Vitamin K levels. 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 Vitamin D) (4).
Vitamin K is very safe
Vitamin K2 is a very safe supplement and the recommended daily dose is likely much lower than the amount for optimum health (5). Be cautious if on warfarin or other medications for blood clotting, otherwise Vitamin K supplements have been used safely in numerous clinical trials including those in pregnancy (6). Consult your healthcare provider if unsure if it is suitable, and make sure to take 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 stay healthier and more elastic, this reduces our risk of high blood pressure and heart problems (7). Higher intake of Vitamin K2 (not K1) reduced the risk of peripheral vascular disease – blocking of the arteries in our bodies (8) in a patient study. Several proteins affected by Vitamin K levels keep our heart and blood vessels healthy (9).
It can affect our blood sugar
Vitamin K supplements can improve our ability to deal with sugar and our insulin levels, helping lower the risk of Type 2 diabetes (10). Decreasing Vitamin K in the diet in animal studies affects their ability to regulate blood sugar (11).
Vitamin K2 deficiency can cause problems with our teeth and increase our risk of cavities
Vitamin K2 is necessary for the development of the mouth and teeth. If low in Vitamin D it can lead to overcrowding of the teeth and issues with the jaw (12). Vitamin K likely helps reduce the risk of dental caries (cavities) affecting saliva and 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 and deficiency can cause calcification (hardening) of the artery walls leading to heart and vascular disease (14). Vitamin K supplements (MK-7 form) improved arterial stiffness (a sign of cardiovascular disease) in post-menopausal women (15) taking supplements for 3 years.
Vitamin K2 has been shown to effectively reduce the risk of Type 2 diabetes (more effectively than Vitamin K1) and seems 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 development of new bone) important for our bone health (17). A large review of postmenopausal women with osteoporosis showed Vitamin K2 helped 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. with steroid use (19). Vitamin K2 has also been shown to be lower in the knees of patients with severe osteoarthritis, suggesting its role in protecting joints from damage (20).
Vitamin K2 (MK-& form) has had promising results in rheumatoid arthritis over standard therapy, improving blood markers of inflammation over 3 months (21). Vitamin D is also important for bone health, which you can read more on here.
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).
- May offset mood effects of sugar – Animal studies show that Vitamin K2 supplements seem to improve anxiety and depression in rats fed a high sugar diet (26).
- Heavy periods – Excessive bleeding (menorrhagia) including during the period can be a sign of Vitamin K deficiency (27).
- Can improve heart output during exercise and therefore cardiovascular fitness in athletes – a small study showed supplementation with Vitamin K2 for 8 weeks improved heart output by 12% (28).
- Liver cirrhosis – Vitamin K2 has been shown to promote liver regeneration and recovery after cirrhosis and partial removal (29).
- SIBO (Small Intestinal Bacterial Overgrowth) – SIBO is often associated with an increased risk of atherosclerosis and this appears to be due to Vitamin K2 deficiency (30).
- Dialysis – 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 that can cause complications and should consider supplements (32).
- Thalassemia major – Vitamin K2 supplements given to children with Thalassemia major, a genetic condition, improved their bone density – a complication of this condition (33).
- Myelodysplastic syndrome – A problem with the bone marrow, anaemia can be improved by Vitamin K supplements (34).
- Pregnancy – Taking a Vitamin K supplement through the late stage of pregnancy can avoid complications of Vitamin K deficiency in the newborn baby (35). It is particularly important for mothers to have good Vitamin K before 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 Vitamin K, instead they do a PPT level called a prolonged prothrombin time, this is a measure of blood clotting which is affected by severe Vitamin K deficiency. Arguably, there is a benefit to supplementing Vitamin K when PPT is unaffected and 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 to do a blood test of Vitamin K itself.
What amount of 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 is also worth noting that Vitamin K2 is a fat-soluble vitamin and therefore cannot be absorbed without fat. However it is very safe at even much higher levels and 1000μg per day or less is considered safe for most people (36).
Top 5 sources of Vitamin K1 in order are:
- 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
Top 5 sources of Vitamin K2 in order are:
- Natto (Vitamin K2) – 800-1000μg per 100g
- Eggs (pasture-raised) 32.1μg per raw egg yolk
- Cheese – Grass fed (especially gouda, blue cheese and cheshire) 16-70μg per 100g
- Grass-fed Butter – 15μg per 100g
- Grass-fed Meat – 4.5-60μg per 100g
THE BEST SOURCES OF K2
Natto – although soy can be an issue, 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 (though this is a bit tricky and requires organic soybeans and a natto culture – you can Google for a lot of online recipes). In Japan natto is often served with steamed rice but it is a bit of an acquired taste!
Fermented food like kefir & sauerkraut – Yet another reason fermented foods are amazing, although natto is the best source – other fermented foods that some find easier to stomach are also good sources of Vitamin K2. Amounts are variable but they have many other benefits. Learn more about kefir here.
Butter and cheese – Hard cheese, soft cheese, aged cheese and butter all are good sources. Gouda and brie are good, and by far the highest amount is found in organic and grass-fed cows, another great reason to eat better sourced food!
Egg yolk – Another wonderful reason to eat eggs, and again organic hens that are pasture-raised (not caged) are far better (they need the Vitamin K1 in the grass to convert to Vitamin K2).
Chicken and chicken liver – Chicken is a good source, particularly chicken liver (which I find easiest to eat as paté like many people who aren’t very partial to liver!)
If you have serious digestive problems including Crohn’s and Coeliac, are taking long term antibiotics or have leaky gut, it is important to consider increasing 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.