Various vitamins and minerals are important, and even critical for heart health. This list of nutrients includes CoQ10, magnesium, vitamin C and vitamin D, that all work through different mechanisms to maintain heart health and prevent risk factors that may lead to heart disease.
However, there is one vitamin that remains relatively unnoticed despite its crucial role in delivering immense benefits to both heart and bone health. We are talking about Vitamin K, which is essentially a group of fat soluble vitamins mostly known for a very important role in blood clotting. There are two types of vitamin K:
Vitamin K1 (phylloquinone): found in green leafy vegetables and vegetable oil
Vitamin K2 (menaquinones): found in fermented foods like natto, cheese and to some extent in dairy foods.
While you need all K vitamins for proper blood clotting, it is vitamin K2 that stands out when it comes to maintaining strong bones and healthy heart functions.
K2 as a heart healthy vitamin
Vitamin K2 serves some really important functions in the body. And one of these roles involve helping the body to properly use calcium.
Calcium is an extremely important mineral that you need for many critical functions, including – formation of strong bones and teeth, muscle contraction, maintaining regular heartbeat, regulating hormone secretion, blood clotting and in transmitting nerve impulses through which nerve cells communicate with each other.
However, too much calcium can cause health problems such as kidney stones, constipation and abnormal contraction of muscles that can result in twitches, muscle cramps and even arrythmia (irregular heartbeat). In addition, excessive calcium can also settle in blood vessels and arteries that can contribute to atherosclerosis (thickening and narrowing of arteries) – a huge risk factor for coronary heart disease leading to angina, heart attack and stroke.
How K2 helps is that it makes sure calcium is directed to the places where it is needed, such as bones and teeth. It also prevents calcium from being deposited in the arteries, kidneys and other soft tissues. So, how does vitamin K achieve this incredibly important feat?
Calcium-Vitamin K2 Relationship
Your skeleton constantly undergoes a process of remodelling, where old bones are broken down by specialized bone cells called osteoclasts and new bones are formed with the help of bone cells called osteoblasts. During this process, the body releases calcium into the bloodstream to maintain calcium levels in the blood and also to maintain skeletal integrity.
Osteoblasts produce osteocalcin, a protein that removes calcium from the bloodstream and binds it to the bone matrix. This process makes the skeleton stronger and less prone to fractures. However, osteocalcin is dependent on vitamin K2 to become fully activated and bind to the calcium circulating in the bloodstream. This is what makes K2 a vital player in bone health, along with nutrients like calcium, vitamin D and magnesium.
So, this is how it goes. You need calcium for healthy bones and vitamin D to absorb this calcium. In addition, you require magnesium to absorb and utilize vitamin D. This is where vitamin K2 steps in as it is required for activating osteocalcin that binds calcium to the mineral component of the bone, thus contributing to the bone health.
Vitamin K2 also helps activate another protein, Matrix Gla-protein (MGP), which is primarily produced by chondrocytes (cells found in cartilage) and vascular smooth muscle cells (cells of the blood vessels that provide structural integrity and are also responsible for healthy contraction and dilation of the blood vessels).
It has been established that MGP is one of the most important proteins involved in preventing accumulation of calcium in the arteries.
Vitamin K2 activates MGP
Since MGP requires vitamin K2 to be fully activated, high levels of inactive MGP circulating in the bloodstream indicate vitamin K deficiency. Inactive MGP is also known as dp-ucMGP.
Inactive MGP, circulating in the blood, has been associated with many adverse health outcomes, such as:
- Arterial stiffness 
- Coronary artery calcification and vitamin K status in healthy women 
- Increased risk of cardiovascular disease in patients with type 2 diabetes 
- Extensive calcification in the peripheral arteries among patients with type 2 diabetes 
- Large artery stiffness in patients with type 2 diabetes 
- Vascular calcification in chronic kidney disease  Vitamin K2 deficiency and heart disease risk
A 2017 research published in Nutrients Journal indicates a strong association between low levels of vitamin K and poor cardiovascular health. The study found that almost one in three participants had vitamin K deficiency; and this prevalence was significantly higher among people who were suffering from other conditions such as high blood pressure, type 2 diabetes, chronic kidney disease, and cardiovascular disease. 
Evidence that Vitamin K2 supplements may help
Previous studies have associated higher intake of vitamin K2 with:
- Reduced arterial calcification and cardiovascular risk 
- Reduced risk of coronary heart disease 
- Reduced coronary artery calcification in post-menopausal women 
- Reduced arterial stiffness in healthy postmenopausal women, especially in women having a high arterial stiffness 
Vitamin K2 versus K1
You need both types of vitamin K for blood clotting. However, there is a difference in how each of these vitamins (K1 and K2) are absorbed and transported to tissues across the body. This is the reason why both K1 and K2 may have different health outcomes.
Vitamin K1, that is primarily found in green leafy vegetables, is not very well absorbed in the body, unless you are combining these foods with some kind of healthy fat. Vitamin K is a fat-soluble nutrient and you need to take it with a healthy fat to enhance absorption.
What is more, vitamin K2 has a longer side chain than K1. This helps K2 to stay longer in circulation. K2, therefore, is better absorbed and utilized by tissues throughout the body, including bone and blood vessels. Vitamin K1 is mostly transported to the liver, where it is used to activate proteins required for blood clotting process.
Most of the studies that confirm vitamin K2’s ability to offer heart health benefits show that it is vitamin K2 and not K1 that is responsible for the cardioprotective effects.
Are you at a risk of vitamin K2 deficiency?
Fermented foods, such as natto, cheese and sauerkraut, are a great source of vitamin K2. Individuals who don’t include fermented foods in their diet are likely to be deficient in this ‘bone and heart healthy’ vitamin. While you may also get some K2 from animal-based products such as meat, eggs and dairy, this amount is not sufficient to maintain a healthy vitamin K2 status in the body.
Other factors that may increase your risk of K2 deficiency include:
- Prolonged use of antibiotics that wipe out the intestinal flora
- Low fat diet as you need fat to absorb and utilize this fat-soluble vitamin
- Gastrointestinal issues such as celiac disease or Crohn’s disease as these conditions can cause poor absorption
- Use of statins (drugs that lower cholesterol)
- Liver disease
- Pivin et al. Inactive Matrix Gla-Protein Is Associated With Arterial Stiffness in an Adult Population-Based Study. Hypertension. 2015
- Dalmeijer et al. Circulating matrix Gla protein is associated with coronary artery calcification and vitamin K status in healthy women. The Journal of nutritional biochemistry. 2013.
- Dalmeijer et al. Matrix Gla protein species and risk of cardiovascular events in type 2 diabetic patients. Diabetes Care. 2013
- Liabeuf at al. Vascular calcification in patients with type 2 diabetes: the involvement of matrix Gla protein. Cardiovasc Diabetol. 2014
- Sardana et al. Inactive Matrix Gla-Protein and Arterial Stiffness in Type 2 Diabetes Mellitus. Am J Hypertens. 2017
- Schurgers et al. The circulating inactive form of matrix gla protein is a surrogate marker for vascular calcification in chronic kidney disease: a preliminary report. Clin J Am Soc Nephrol. 2010
- Riphagen et al. Prevalence and Effects of Functional Vitamin K Insufficiency: The PREVEND Study. Nutrients 2017.
- J.M. Geleijnse, et al., 'Dietary Intake of Menaquinone is Associated with a Reduced Risk of Coronary Heart Disease: The Rotterdam Study,' J. Nutr. 134, 3100–3105 (2004).
- G.C. Gast, et al., 'A High Menaquinone Intake Reduces the Incidence of Coronary Heart Disease,' Nutr. Metab. Cardiovasc. Dis. 19, 504–510 (2009).
- Beulens et al. High dietary menaquinone intake is associated with reduced coronary calcification. Atherosclerosis. 2009
- Knapen et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial. Thromb Haemost. 2015
- Mansour et al. Vitamin K2 supplementation and arterial stiffness among renal transplant recipients-a single-arm, single-center clinical trial. J Am Soc Hypertens. 2017
- Townsend R.R. Arterial stiffness and chronic kidney disease: lessons from the chronic renal insufficiency cohort study. Curr. Opin. Nephrol. Hypertens. 2015