In the nutrition world, some vitamins are important to our health, but don’t stand out. While we tend to hear a lot about the importance of vitamins C and D lately, we need to keep in mind that there are other vitamins out there that support the functions of our bodies, and that without them, other vitamins can’t do their jobs.

What Is Vitamin K?

Vitamin K is a fat-soluble micronutrient that is important in protein synthesis and other bodily functions. There are two main types of vitamin K that are found in nature. Vitamin K1 is mostly found in green leafy vegetables and is also called phylloquinone. Vitamin K2, on the other hand, is found mostly in animal products and some fermented foods. These nutrients are not often talked about, but they do play an important role in bodily and specifically cellular functions. Vitamin K1 is more abundantly found in foods, and can be converted to K2 in the gut and then used by the body.

What Does Vitamin K Do in the Body?

Vitamin K functions as a co-enzyme that aids in the synthesis of proteins involved in many different functions. For example, the formation of proteins involved in blood clotting and bone metabolism depend on vitamin K supplies in the body. Vitamin K helps form a protein called osteocalcin which is necessary for high bone mineral density and overall healthy bones. Vitamin K may also help prevent vascular calcification which is a process that can lead to coronary heart disease.1 Vascular calcification occurs when there is an insufficient amount of matrix GLA protein in the body and calcium can build up in the arteries, causing them to stiffen. This can become a problem in many people, especially older people who take calcium supplements, but do not get sufficient vitamin K in their diet. Calcium accumulates in blood vessels throughout the body and leads to a higher risk of heart attack by 86 percent compared to those not taking a calcium supplement.2

What Happens When You Have a Deficiency?

A major result of vitamin K deficiency is low bone mineral density, which can contribute to weak bones and can lead to osteoporosis over time. Vitamin K deficiency often occurs shortly after birth if the nutrient is not properly transferred through the placenta to the fetus during pregnancy. Vitamin K deficiency can be severe, and in such cases will result in hemorrhaging. This can be fatal in some cases, especially if the deficiency is chronic and occurs during infancy.1 In fact, the fatality rate for neonatal vitamin K deficiency is 62 percent, though the occurrence of the deficiency is only about 38.2 out of 100,000 infants on average.

How Do You Get Enough Vitamin K?

Vitamin K is abundant in vegetables like kale, collard greens, spinach, edamame and broccoli in the form of phylloquinone (vitamin K1). This form of vitamin K can then be converted by the body into vitamin K2. Natto (a soy product) along with animal products like salmon, eggs and milk all contain small amounts of vitamin K in the form of menaquinone (vitamin K2). There are also many supplements that contain different forms of vitamin K along with other nutrients like calcium and vitamin D. Vitamin K is also commonly found in daily multivitamins. These forms of vitamin K are well absorbed by the body and tend to be quite bioavailable, though more studies are needed to confirm the extent of their bioavailability.1 Frunutta makes a sublingual line of vitamins, including vitamin K2, that dissolve right under the tongue, and they contain no fillers or additives.

How Much Vitamin K Do You Need and Can You Overdo It?

For adult women, the recommended daily allowance is 90 mcg and for adult men it is 120 mcg. The intake requirement for vitamin K increases sharply over time. During infancy, recommended intake is only 2 mcg, at 8 years old it is 55 mcg and at 14 it becomes 75 mcg.1 There is not much evidence about the effects of vitamin K toxicity, but it is possible for vitamin K to build up in the body, especially in formula-fed infants, resulting in anemia and jaundice. While this is rare, and very few adults will experience vitamin K toxicity, it is still something to be cognizant of with newborns.3

Other Things to Know About Vitamin K

Some medications can have adverse interactions with vitamin K that can be potentially dangerous. Since vitamin K2 is often synthesized in the gut, prolonged use of antibiotics can result in the destruction of gut bacteria that processes phylloquinone into vitamin K2. Over time this can lead to a vitamin K deficiency.

Anticoagulants can also negatively impact levels of vitamin K in the body. Anticoagulants are used to prevent blood clotting and can interact with several clotting factors that depend on vitamin K for their function. For this reason, it is important that those taking anticoagulants keep a close eye on their vitamin K intake to make sure it remains consistent.1

Conclusion

Vitamin K is a little talked about, but vital micronutrient. It helps maintain high bone mineral density and keeps calcium deposits out of arteries and other blood vessels. Chronic vitamin K deficiency can increase risk for osteoporosis as well as heart attacks if left untreated. Fortunately, it is not difficult to get vitamin K from food sources. Phylloquinone, or vitamin K1, is much more abundant in plant foods like kale, broccoli and spinach, but, like many vitamins, it can be converted into vitamin K2 in the body in order to be put to use.

References:

1 National Institutes of Health Office of Dietary Supplements (2021). Vitamin K. Retrieved from: https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/#h7.

2 Maresz K. Proper Calcium Use: Vitamin K2 as a Promoter of Bone and Cardiovascular Health. Integrative Medicine: A Clinician’s Journal (2015). 14(1): 34-39. Retrieved from: www.ncbi.nlm.nih.gov/pmc/articles/PMC4566462/.

3 Johnson LE. Vitamin K Excess. Merck Manual Consumer Version (2020). Retrieved from: www.merckmanuals.com/home/disorders-of-nutrition/vitamins/vitamin-k-excess#:~:text=Vitamin%20K%20is%20necessary%20for,a%20type%20of%20brain%20damage). VR

Dr. Nicole Avena is a research neuroscientist and expert in the fields of nutrition, diet and addiction, with a special focus on nutrition during early life and pregnancy. Her research achievements have been honored by awards from several groups including the New York Academy of Sciences, the American Psychological Association, and the National Institute on Drug Abuse. She is an assistant professor of neuroscience at the Ichan School of Medicine at Mount Sinai, in New York, NY and is a visiting professor of health psychology at Princeton University in New Jersey. Avena has written several books, including What to Eat When You’re Pregnant and What to Feed Your Baby and Toddler. She regularly appears as a science expert on the Dr. Oz Show, Good Day NY and The Doctors, as well as many other news programs. Her work has been featured in Bloomberg Business Week, Time Magazine for Kids, The New York Times, Shape, Men’s Health, Details, as well as many other periodicals. Avena blogs for Psychology Today, is a member of the Penguin Random House Speakers Bureau and has the No. 2 most watched TED-ED Health talk, “How Sugar Affects Your Brain.” You can follow Avena on Twitter (@DrNicoleAvena), Facebook (www.facebook.com/DrNicoleAvena) and Instagram (@drnicoleavena), or visit www.drnicoleavena.com.