Vitamin K2 is one of the main forms of vitamin K. It was discovered at the beginning of the last century during research into the connection between food and health. At first the vitamin was called "Activator X", but later took the name K2. Vitamin K itself had been discovered in Germany shortly before, under the name Koagulationsvitamin — "coagulation vitamin" — and the present name comes from the first letter of that German word.
There are two main forms: vitamin K1 (phylloquinone), found in some plant foods such as leafy greens, and vitamin K2 (menaquinone), found in fermented foods and in foods of animal origin. Vitamin K2 divides further into several subtypes, the most important being MK-4 and MK-7.
The role of vitamin K2
Vitamin K2 acts as an activator of certain proteins that contribute to normal blood clotting, to optimal calcium metabolism and to the health of the heart muscle.
One of its most important functions is regulating calcium and its deposition in the skeletal system. In other words, vitamin K2 encourages the calcification of bone while at the same time preventing the calcification of blood vessels and kidneys.
Some studies show that vitamin K2 (MK-4) reduces the calcification of blood vessels, while vitamin K1 shows no such property. Research also observes that K2 supplements generally improve the health of bones and heart, while K1 brings no significant benefit in this respect. This is why scientists consider that K1 and K2 should be classified as separate nutrients rather than as one micronutrient under the common name vitamin K.
How to get vitamin K2
Vitamin K1 occurs in many foods; unfortunately that is not the case for K2, which is absent from most dietary sources. It is found mainly in fermented foods such as sauerkraut, kefir, apple cider vinegar and natto. Vitamin K2 can also be converted in the body from vitamin K1, and partly synthesised by the useful gut bacteria — but because of the excessive use of broad-spectrum antibiotics and other unfavourable factors, these processes are impaired in most people.
Foods rich in vitamin K2 include higher-fat dairy products, egg yolks, liver and, as mentioned, probiotic foods. Vitamin K2 is fat-soluble, which means it is absent from low-fat sources. Foods of animal origin contain the MK-4 subtype, while fermented foods offer the longer subtypes, from MK-5 to MK-14.
Because the amounts in these foods are small and they are eaten less often, the average intake of vitamin K2 is remarkably low. For this reason specialists recommend taking a K2 supplement regularly. The benefits can be strengthened further when combined with a vitamin D supplement, since the two vitamins act synergistically — their effect increases when they work as a team.
In our shop you can read more about the natto supplement, an excellent source of vitamin K2, and look at our vitamin D products, such as this bone health nutrient complex.
The benefits of vitamin K2
Vitamin K2 is associated with a number of favourable effects on health. It strengthens the bones, contributes to blood clotting and supports the normal working of the cardiovascular system.
It improves bone health and lowers the risk of osteoporosis
Vitamin K2 is of first importance for calcium metabolism. Calcium is the main mineral involved in building bones and teeth. K2 activates two proteins important to the skeletal system (GLA protein and osteocalcin) that help build and maintain healthy bone and tooth enamel.
When the amount of calcium in bones and joints is insufficient, because of a deficiency or poor regulation of minerals, osteoporosis can set in. The condition is characterised by porous, brittle bone of low density. Osteoporosis is one of the most common skeletal conditions in the Western world, seen mainly in older people and linked to a raised risk of fractures.
Research shows that people who take a vitamin K2 supplement regularly enjoy stronger bones and suffer less often from the age-related decline in bone mineral density. Some studies report a reduced risk of spinal fractures by up to 60%, of hip fractures by up to 75% and of fractures elsewhere in the skeleton by up to 80%.
It supports the health of the heart and blood vessels
Abnormal regulation of calcium in the body can cause it to accumulate excessively in the arteries, which sets the stage for cardiovascular disease. This state is known as arterial calcification and can lead to high blood pressure, atherosclerosis, stroke and heart attack. Vitamin K2 has been found to help regulate calcium in the blood vessels normally, which contributes to a lower risk of heart disease.
Clinical research shows that the risk of arterial calcification in people with an optimal K2 intake is half as high. In this group up to 55% fewer deaths from heart attack and stroke are also observed. Studies indicate that the credit for this belongs to vitamin K2; K1 has no established contribution.
What the research says about K2 and cancer
Studies in oncology have looked at vitamin K2 in relation to the recurrence of certain cancers. A pilot study by Mizuta and colleagues (2006) examined menatetrenone, a vitamin K2 analogue, in patients with hepatocellular carcinoma after curative treatment. Other observational research has associated a higher K2 intake with a lower risk of prostate cancer.
These are research findings, not a treatment. Vitamin K2 is not a means of preventing or treating cancer, and no supplement should replace medical care.
The recommended daily intake of vitamin K2
The recommended daily intake for adults is in the order of 100–300 micrograms. Children under 12 need 45 micrograms a day. People with certain medical conditions, and those over 55 or in the menopause, may need more vitamin K2; in that case it is best to consult your doctor.
No overdose or serious side effects from taking too much vitamin K2 are known. Even so, it is sensible to keep to the recommended intake.
Important: if you take anticoagulant medicines (such as warfarin), vitamin K interferes directly with their action — do not start a supplement without speaking to your doctor.
Sources
- Schurgers, L. J. (2006). Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7.
- Theuwissen, E., et al. (2012). The Role of Vitamin K in Soft-Tissue Calcification. Advances in Nutrition.
- Geleijnse, J. M., et al. (2004). Dietary Intake of Menaquinone Is Associated with a Reduced Risk of Coronary Heart Disease: The Rotterdam Study. The Journal of Nutrition.
- Shearer, M. J., et al. (2012). Vitamin K Nutrition, Metabolism, and Requirements.
- Kidd, P. M. (2010). Vitamins D and K as pleiotropic nutrients.
- Mizuta, T., et al. (2006). The effect of menatetrenone, a vitamin K2 analog, on disease recurrence and survival in patients with hepatocellular carcinoma after curative treatment.
