Out of all the essential nutrients that our bodies require from our diets, vitamin K might be one of the most underappreciated. If you haven’t read about vitamin K before or heard about its benefits from your doctor, that is probably because most of us already get enough from our diets to avoid vitamin K deficiency. But, as you will learn, there are some benefits to be gained from consuming more vitamin K than the minimum requirement. What exactly is vitamin K, and what does vitamin K do for the body? Read on to find out and to discover how you can include more vitamin K in your diet.
What is vitamin K?
Vitamin K is a fat-soluble vitamin which is needed for the function of several proteins in the body. It occurs naturally in two forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). K1 and K2 are needed for the carboxylation (addition of a carboxyl group) of vitamin K-dependent proteins. Carboxylation is needed to activate these proteins so they can carry out their functions. Some proteins that depend on vitamin K for carboxylation include coagulation factors, bone-forming proteins, and anticalcification proteins (1). All of these proteins have significant roles in the proper functioning of the human body. Here are the main ways that vitamin K contributes to our health.
Greater bone strength
Osteoporosis affects millions of people worldwide and is a major cause of bone fractures. In the past, calcium and vitamin D supplements have been recommended to support bones, and these are probably the first nutrients that come to mind when you think of bone health. These nutrients have been shown in clinical studies to strengthen bones and lower the risk of osteoporosis. However, more of these nutrients is not always better, and an excess of calcium can actually build up in blood vessels, causing cardiovascular disease and death (2).
Vitamin K has been explored as an alternative supplement for building bone strength and has shown some promising results. One study followed postmenopausal women with osteopenia (reduced bone mass of less severity than osteoporosis) over two years. In this study, the women who were given vitamin K1 had a 50% reduction in bone fractures compared to those who were given a placebo. Additionally, a meta-analysis has shown that large doses (45 mg/day) of vitamin K2 reduces fractures significantly (1).
Vitamin K is so important for bone health because it is needed to activate osteocalcin, a protein that takes calcium from the blood stream and binds it to the bone matrix (2). Studies suggest that either K1 or K2 can be taken to increase bone strength and reduce fractures, but so far the evidence is stronger in favor of the K2 form.
Improved cardiovascular health
The functions of vitamin K are interconnected with calcium in multiple ways. Vitamin K not only helps calcium to strengthen bones, but also alleviates the negative effects of calcium. As mentioned earlier, excess calcium can cause vascular calcification, the buildup of calcium in the blood vessels. Consequently, calcium supplementation has been associated with an increased risk of cardiovascular events and coronary heart disease. One study with almost 24,000 participants found that those taking calcium supplements had an 86% increase in risk of heart attack.
As this and other studies show, the regulation of calcium is essential to cardiovascular health, especially for people who take calcium supplements. Thankfully, vitamin K helps to regulate calcium and prevents its negative effects. It does this by activating matrix gla protein (MGP), which inhibits the deposition of calcium in blood vessels. Multiple studies with thousands of participants have shown that a high dietary intake of vitamin K2 is associated with lower risk of coronary heart disease, mortality, and aortic calcification. However, vitamin K1 has not shown any of the cardiovascular benefits associated with K2 (2).
Vitamin K deficiency
Clinically significant vitamin K deficiency is a rare problem, but sub clinical deficiency is more common. Many people take in sub optimal levels of K2 in particular due to its low availability in the typical Western diet. In fact, it is estimated that 30% of vitamin K-dependent proteins remain inactivated due to low vitamin K2 intake (2). These include proteins that are essential for vascular decalcification and cardiovascular function. It is easy to see how a low intake of vitamin K over time could cause human health to suffer significantly.
There is an additional concern for patients taking the blood thinner warfarin. This medication directly inhibits vitamin K, leading to increased vascular calcification and the associated cardiovascular effects. Based on animal studies, high doses of vitamin K1 or K2 may be able to reverse these effects, but this has not been confirmed in humans (1).
Sources of vitamin K
Although vitamin K is not the most well-appreciated nutrient, hopefully you can now recognize hownecessary it is for your cardiovascular and bone health. So, how can you ensure you are getting enough of this essential vitamin? For phylloquinone (K1), you have many options and it is not difficult to get enough as part of a healthy diet. K1 is found in leafy greens such as kale, spinach and lettuce; vegetables such as broccoli, brussels sprouts, and cabbage; vegetable oils, and some fruits (3). Menaquinone (K2) is more difficult to find, and data is limited regarding its presence in food. K2 can be found in some fermented foods such as a Japanese form of fermented soybeans called natto.
Dietary supplements can help ensure that you obtain enough vitamin K to keep your bones strong and regulate calcium in your blood vessels. Because K1 is closely bound to chloroplasts in whole plant foods, it has a very low bioavailability. More K1 can be absorbed from oils and supplements than from plants. As mentioned, K2 is naturally produced only in certain fermented foods, and few foods are fortified with K2. This means that a supplement is the easiest way to obtain this vitamin K2.
Most multivitamins contain a form of vitamin K, so you might not find it necessary to buy a separate vitamin K supplement. Look for a multivitamin that contains vitamin K2 since this form is the hardest to obtain and the most important for cardiovascular health. If you think a separate vitamin K supplement could be beneficial, you can get some vegan K2 naturally sourced from chickpeas here.
I hope this has given you a better understanding of what vitamin K does for the body and how you might benefit from increasing your intake. The greatest lesson I have learned from researching vitamin K is that optimum health can be achieved only by properly balancing the nutrient levels in our bodies. Certain minerals such as calcium are beneficial only when taken in moderate amounts and balanced with vitamins such as K2. A healthy lifestyle is an ongoing process, but the proper balance of nutrients from both plants and supplements makes it much more achievable.
1. DiNicolantonio, J. J., Bhutani, J., & O’Keefe, J. H. (2015). The health benefits of vitamin K. Open Heart, 2(1), e000300. http://doi.org/10.1136/openhrt-2015-000300
2. Maresz, K. (2015). Proper Calcium Use: Vitamin K2 as a Promoter of Bone and Cardiovascular Health. Integrative Medicine: A Clinician’s Journal, 14(1), 34–39.
3. Office of Dietary Supplements – Vitamin K. (n.d.). Retrieved August 24, 2018, from https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/#h3