Amid all the hoo-ha about vitamins, minerals and antioxidants, chances are that, unless you’re a nutritional scientist or dietician, you’ve never even heard of vitamin K2.
However, once you read why so many researchers are excited about the key role this vitamin can play in preventing heart disease, osteoporosis and possibly cancer, you might want to place it higher on your list of priority nutrients.
A brief history of vitamin K
Way back in 1929, when researchers first discovered vitamin K (VK), they focused mainly on the vital role of this fat-soluble vitamin in the blood-clotting process (coagulation). To this day, it’s still known as the “clotting vitamin”, even though research shows it plays many other important roles.
At the time, researchers identified three basic forms of VK – vitamin K1 (phylloquinone), vitamin K2 (menaquinone or MK) and vitamin K3 (menadione), a potent synthetic form of vitamin K not used in humans.
They initially considered these to be straightforward structural variations of VK. Several years later, however, they discovered that each form of VK also has subtype compounds. For example, vitamin K2 has the subtypes MK4 (found in animal products like meat and dairy) and MK7, a natural product of the bacteria that live in the lower intestine.
Read: What is vitamin K?
Some alternative medical practitioners have claimed that vitamin K3 is an anti-cancer agent that helps to slow or stop tumour growth when taken in high doses together with vitamin C. However, much more research needs to be done before firm recommendations can be made.
While scientists continue studying all forms of VK, and how they can impact on human health, the spotlight has in recent years shifted to vitamin K2 as a distinctly different vitamin, deserving far more attention.
It’s now becoming clear that VK2 may help to prevent a host of serious conditions such as heart disease, osteoporosis and even cancer.
Vitamin K2, cholesterol and the heart
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The main role of VK2 is to bind with calcium. This helps bone-building cells to incorporate the mineral into the bones’ structural matrix, according to Professor Tim Crowe of the School of Exercise and Nutrition Sciences at Australia’s Deakin University.
VK2 is now also thought to help prevent the dangerous accumulation of calcium salts in the blood vessels, or so-called vascular calcification.
Studies have shown that even modest amounts of VK2 fight heart disease by controlling calcium-regulating proteins in vascular tissue. This keeps calcium out of the arteries and prevents dangerous calcified plaques – and atherosclerosis – from developing.
While more research needs to confirm early findings, this certainly holds promise for the prevention and treatment of heart disease in future.
Vitamin K2 and the bones
Various factors play a role in optimising bone health. Dietary calcium, while best known, is only one important nutrient for preventing bone degeneration. “Other factors such as vitamin D and magnesium intake, low-grade systemic inflammation, weight-bearing exercise, and intestinal health, also impact bone-mineral density – and VK2 should be added to the list,” says registered dietician Aglaée Jacob in an article in Today’s Dietician.
Jacob explains that VK2 helps to activate osteocalcin, a protein secreted by bone-building cells called osteoblasts, which draws calcium into the bones. This helps the mineral to be incorporated into the bone matrix.
In addition, vitamin K2, when combined with vitamin D3, helps inhibit osteoclasts, the specialist cells responsible for bone resorption. Bone resorption is a process that occurs continually inside the body. Osteoclasts break down bone, which is then replaced with new bone growth. As we get older, the rate of bone breakdown (resorption) tends to exceed the rate of replacement, leading to conditions like osteoporosis.
Read: How women get osteoporosis
Studies show that the Japanese population appears to be at lower risk for bone fractures compared to people in Europe and America. The higher levels of bone-mineral density (BMD) among the Japanese have largely been attributed to the country’s widespread consumption of VK2-rich natto (fermented soy beans).
This traditional breakfast food is associated with a significantly lower risk of hip and spinal fractures in the Japanese population, compared with other countries where natto is seldom or never eaten.
Vitamin K and cancer
In addition, a few small clinical trials have shown that certain subtypes of the vitamin K group – specifically VK3 (nenadione) and menatetrenone (MK4), a subtype of VK2 – shows some promise in the field of cancer prevention and treatment.
One of these pilot studies examined whether VK3 can help overcome the resistance of cancer cells to certain types of chemotherapy drugs. In 2006, another clinical trial suggested that MK4 may be able to limit the recurrence of liver cancer after surgery.
While some clinical trials on humans have begun, further study is needed to establish whether VK subtypes may help prevent or treat cancer.
How to add vitamin K2 to your diet
With VK2 occurring in far smaller quantities in our diets than vitamin K1 (found predominantly in leafy green vegetables and certain vegetable oils), most people consume too little vitamin K2-rich foods. In addition, the very small amounts the body stores are rapidly depleted without regular dietary intake.
Professor Crowe and Aglaée Jacob say that animal food products, especially liver, chicken, beef, bacon and ham, are excellent sources of VK2. While natto is by far the richest source of vitamin K2, it’s an acquired taste that many Westerners may not find palatable. Fermented foods such as sauerkraut and kimchee are alternatives.
Egg yolks (not egg whites) also provide valuable amounts, as do high-fat dairy products, adds Jacob. Modest quantities of VK2 are also found in traditionally fermented cheeses, especially Swiss Emmental and Norwegian Jarlsberg.
Some studies recommend supplementation as a way to increase vitamin K2 intake, instead of foods. This could be especially important in the diets of vegetarians, who don’t consume animal foods.
Aglaée Jacob remarks that VK2 supplementation is available in different forms. These include MK4, a synthetic version produced from an extract of the Nicotiana tabacum plant, and MK7, a more natural form sourced from natto.
How much vitamin K2 do we need?
With significant gaps in current knowledge on VK2, Prof Crowe remarks that the amount of VK2 needed every day is unknown. Current recommendations are based on total vitamin K intake, which is about 60 to 90 micrograms per day.
What makes it tricky is that current dietary guidelines for vitamin K focus on how much is needed to regulate blood clotting. The much higher amount needed to maintain healthy bones and arteries is still under investigation.
While the current Dietary Reference Intake for vitamin K doesn’t differentiate between the different types, this will hopefully change in future. In the meantime, Jacob says it’s important to know that food sources of vitamins K1 and K2 are different. She adds that while vitamin K1 deficiency is rare and almost non-existent, vitamin K2 deficiency is prevalent.
So, even if you’re not quite sure how much VK2 you should be consuming, the good news is that there’s no known toxicity associated with high doses of VK2, according to researcher Joline Beulens. She explains that, unlike the other fat-soluble vitamins, vitamin K is not stored in any significant quantity in the liver. Therefore, toxicity isn’t a problem.
According to Professor Crowe, people taking anticoagulants (blood-thinning drugs) such as warfarin (Coumarin, Jantoven) need to be extra careful when taking vitamin K2 supplements. Consult your doctor before taking supplements because of its role in blood clotting.
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