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Vitamin K1 Versus K2: The Difference And Their Relevance

The Differences Between Vitamins K1 And K2

Vitamin K1 is abundant in plant sources such as green leafy vegetables like spinach, kale, and broccoli. Vitamin K2 is found in meat, dairy products, eggs, and fermented foods like cheese. Vitamin K is essential for heart health, bone strength, the prevention of bleeding disorders, and treatment of diseases like Alzheimer’s disease. Vitamin K supplements should be used carefully as they may interact with blood-thinning medications.

The recommended dietary intake of vitamin K stands at 122 mcg for women and 138 mcg for men. Not having enough of the vitamin could cause excessive bleeding in wounds, gums, gastrointestinal tract, or nose as well as heavy menstrual periods and bone density loss.1

Whether you are trying to increase your intake of vitamin K, have a deficiency, or are simply curious, it’s worth understanding everything that falls under this essential nutrient.

Vitamin K refers to a group of fat-soluble vitamins (which means they’re stored in fatty tissues and the liver once they’re absorbed and are best had with fatty foods) that share similar chemical structures. Although there are several types of vitamin K, the most common ones found in the human diet are vitamin K1 and K2.  K1, also known as phylloquinone, is a natural form of vitamin K that accounts for 75–90% of all the vitamin K consumed by humans. On the other hand, K2 is produced by certain bacteria in the intestines and has several subtypes called menaquinones (MKs) that are named by the length of their side chain and range from MK-4 to MK-13. Each of these plays a significant role in several critical body functions.2

K1 Regulates Blood Clotting, K2 Protects The Heart

A healthy, balanced diet includes both vitamin K1 and K2. This is because each of them have a role to play in different functions of the body, which include:

  • Blood clotting: Vitamin K1 plays a critical role in the clotting of blood and its deficiency can cause bleeding disorders. That said, recent research has pointed out that vitamin K2 is just as important. In fact, one study found that a single serving of vitamin K2-rich natto altered measures of blood clotting for up to four days. So, be sure to mix up your sources of vitamin K.3

One study suggests that vitamin K supplementation may treat individuals with Alzheimer’s disease by reducing damage to neurons in the body from cardiovascular diseases.4 However, further research is needed to fully understand which of the two K vitamins are more crucial.

  • Bone health: Vitamin K2 takes the cake when it comes regulating the calcium present in the body. It is vital for the bones and their mineralization – a process of laying down minerals on the matrix of the bone. This could be why supplements of vitamin K2 play a role in treating bone-related illness. However, research indicates that low levels of either vitamin K1 or K2 might lead to an increased risk of bone loss, although the evidence is very inconsistent and needs further research. That said, the research has prompted governments to stress on the importance of both vitamin K1 and K2 for bone health.5
  • Heart Health: Vitamin K activates a protein that prevents calcium from depositing in the arteries. These calcium deposits lead to the development of plaque which leads to heart disease. Some studies have shown that vitamin K2 might be more beneficial than vitamin K1 when it comes to this benefit.6 However, quality-controlled studies state that both K vitamins are vital to prevent calcium build-up.7 8

Deficiency of this vitamin may occur in individuals which chronic conditions (like cancer, gallbladder disease, cystic fibrosis, celiac disease, chronic pancreatitis, or Crohn’s disease) which hamper fat absorption and in turn, the absorption of vitamin K. Additionally,  infants who don’t receive a vitamin K injection at birth, who are solely fed breastmilk (which is low in vitamin K), or whose mothers take anticonvulsants (for seizures) and anticoagulants (for clotting disorders) as well as vegans (due to the elimination of animal sources of vitamin K) are at risk of a deficiency.9 Thankfully, knowing the sources of the vitamin can help make better dietary choices.

K1 Is Found In Vegetables, K2 Is Found In Animal Products

Leafy green vegetables, legumes, and vegetable oils are common dietary sources of vitamin K1. The greener the better too, as the outer green layers are richer than the pale inner leaves.

Here are the most common sources of vitamin K1 along with the amount of the vitamin you will get per cup of the cooked vegetable:10

  • Spinach: 888.5 mcg11
  • Broccoli: 110.1 mcg12
  • Iceberg lettuce: 20.0 mcg13
  • Kale: 493.8 mcg14
  • Collard greens: 772.5 mcg15
  • Brussels sprouts: 109.4 mcg16

Fruits and vegetable peels are also believed to be rich in vitamin K so try to incorporate them into your meals and not throw them out.17

Vitamin K2 is found mostly in animal-based foods such as meat, dairy foods, and eggs.18 That said, these sources vary depending on the subtypes of the vitamin that we’d mentioned earlier. For instance, good sources of MK-4 are animal products. This is is the only form of vitamin K2 that is not produced by bacteria. Here’s a list of the sources of vitamin K2 with the subtype MK-4:

  • Chicken, leg and thigh: 60 mcg
  • Egg yolk: 32 mcg
  • Whole milk: 3.4 mcg

That aside, MK-5 through MK-15 have longer side chains, are produced by bacteria, and are often found in fermented foods. Here’s a list of foods that will give you this nutrient along with the specific subtype:

  • Natto, a Japanese dish made from fermented soybeans: 1,062 mcg (subtype MK-7)19
  • Pork sausage: 383 mcg (subtype MK-10 and MK-11)20
  • Hard cheeses: 76 mcg (subtype MK-8 and MK-9)21
  • Soft cheeses: 57 mcg (MK-8 and MK-9)22

Hydrogenated plant oils decrease the absorption of vitamin K in the bones due to the presence of trans-fatty acids. Regular use of certain drugs such as antibiotics and a poor diet can deplete the levels of vitamin K in your body.

Note: The only vegan source of vitamin K2 is natto. If you’re vegan, do consider including this dish in your diet or talk to a medical professional about supplementation.

K2 Is Better Absorbed And Circulated In The Body Than K1

As we’d mentioned earlier, the main function of all the different types of vitamin K is to ensure that all the proteins that are involved in the process of blood clotting, heart function, and bone health are activated. That said, they differ when it comes to:

  • Absorption: Depending on the amount of fat in the food source of the vitamin, the absorption rates for both types vary. Vitamin K1 found in plants is poorly absorbed by the body. In fact, research indicates that less than 10% of the vitamin found in plant sources is absorbed.23 Alternatively, while very little is known about the absorption of vitamin K2, researchers state that considering how most sources of this specific vitamin are high in fat, vitamin K2 might be better absorbed than K1.24
  • Circulation time in the blood: The length of the side chain can determine how long each specific K vitamin circulates in the blood.25 Vitamin K2’s long side chain allows it to circulate in the blood longer than K1, with the former remaining in the blood for days. This allows it to be better used in tissues located throughout the body. Alternatively, vitamin K1 may stay in the blood for several hours during which it is primarily transported to and used by the liver.26

These differences are crucial to the benefits that vitamin K provides with each contributing differently.

A Word Of Caution: Vitamin K and Medications

Vitamin K is known for its anti-clotting properties. For this reason, supplements of vitamin K and prescribed blood thinners like anticoagulants such as warfarin and heparin or other drugs may counteract with each other.27 If you are on blood thinners, keep your doctor informed when vitamins are prescribed and even if you need to pop an additional aspirin.

In addition, certain cholesterol-lowering medications may reduce the amount of fat your body absorbs and may also reduce the absorption of fat-soluble vitamins like vitamin K.

Therefore, vitamin K is an essential nutrient for the normal functioning of the human body and can be provided in adequate amounts through a balanced, healthy diet. In case of a deficiency, always consult your doctor before taking supplements.

References   [ + ]

1. Vitamin K. US Department Of Health And Human Services.
2. El Asmar, Margueritta S., Joseph J. Naoum, and Elias J. Arbid. “Vitamin k dependent proteins and the role of vitamin k2 in the modulation of vascular calcification: a review.” Oman medical journal 29, no. 3 (2014): 172.
3. Schurgers, Leon J., Martin J. Shearer, Karly Hamulyák, Elisabeth Stöcklin, and Cees Vermeer. “Effect of vitamin K intake on the stability of oral anticoagulant treatment: dose-response relationships in healthy subjects.” Blood 104, no. 9 (2004): 2682-2689.
4. Allison, A. C. “The possible role of vitamin K deficiency in the pathogenesis of Alzheimer’s disease and in augmenting brain damage associated with cardiovascular disease.” Medical hypotheses 57, no. 2 (2001): 151-155.
5. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). “Scientific Opinion on the substantiation of health claims related to vitamin K and maintenance of bone (ID 123, 127, 128, and 2879), blood coagulation (ID 124 and 126), and function of the heart and blood vessels (ID 124, 125 and 2880) pursuant to Article 13 (1) of Regulation (EC) No 1924/2006.” EFSA Journal 7, no. 10 (2009): 1228.
6. Weber, Peter. “Vitamin K and bone health.” Nutrition 17, no. 10 (2001): 880-887.
7. Gast, Gerrie-Cor M., Nicole M. de Roos, Ivonne Sluijs, Michiel L. Bots, Joline WJ Beulens, Johanna M. Geleijnse, Jacqueline C. Witteman, Diederick E. Grobbee, Petra HM Peeters, and Yvonne T. van der Schouw. “A high menaquinone intake reduces the incidence of coronary heart disease.” Nutrition, Metabolism and Cardiovascular Diseases 19, no. 7 (2009): 504-510.
8. Shea, M. Kyla, Christopher J. O’Donnell, Udo Hoffmann, Gerard E. Dallal, Bess Dawson-Hughes, José M. Ordovas, Paul A. Price, Matthew K. Williamson, and Sarah L. Booth. “Vitamin K supplementation and progression of coronary artery calcium in older men and women–.” The American journal of clinical nutrition 89, no. 6 (2009): 1799-1807.
9. Vitamin K Deficiency. American Association For Clinical Chemistry.
10, 18. Vitamin K. National Institutes of Health.
11. Full Report (All Nutrients): 11458, Spinach, cooked, boiled, drained, without salt. United States Department Of Agriculture.
12. Basic Report: 11091, Broccoli, cooked, boiled, drained, without salt. United States Department Of Agriculture.
13. Full Report (All Nutrients): 45064006, FRESH SHREDDED ICEBERG LETTUCE, UPC: 071430010655. United States Department Of Agriculture.
14. Basic Report: 11234, Kale, cooked, boiled, drained, without salt. United States Department Of Agriculture.
15. Basic Report: 11162, Collards, cooked, boiled, drained, without salt. United States Department Of Agriculture.
16. Full Report (All Nutrients): 11099, Brussels sprouts, cooked, boiled, drained, without salt. United States Department Of Agriculture.
17. Booth, Sarah L., James A. Sadowski, John L. Weihrauch, and Guylaine Ferland. “Vitamin K1 (phylloquinone) content of foods: a provisional table.” Journal of Food Composition and Analysis 6, no. 2 (1993): 109-120.
19. Kamao, Maya, Yoshitomo Suhara, Naoko Tsugawa, Masako Uwano, Noriko Yamaguchi, Kazuhiro Uenishi, Hiromi Ishida, Satoshi Sasaki, and Toshio Okano. “Vitamin K content of foods and dietary vitamin K intake in Japanese young women.” Journal of nutritional science and vitaminology 53, no. 6 (2007): 464-470.
20. Fu, Xueyan, Xiaohua Shen, Emily G. Finnan, David B. Haytowitz, and Sarah L. Booth. “Measurement of multiple vitamin K forms in processed and fresh-cut pork products in the US food supply.” Journal of agricultural and food chemistry 64, no. 22 (2016): 4531-4535.
21. Schurgers, Leon J., and Cees Vermeer. “Determination of phylloquinone and menaquinones in food.” Pathophysiology of Haemostasis and Thrombosis 30, no. 6 (2000): 298-307.
22. L. Booth, Sarah. “Vitamin K: food composition and dietary intakes.” Food & nutrition research 56, no. 1 (2012): 5505.
23. Gijsbers, Birgit LMG, Kon-Siong G. Jie, and Cees Vermeer. “Effect of food composition on vitamin K absorption in human volunteers.” British Journal of Nutrition 76, no. 2 (1996): 223-229.
24. Beulens, Joline WJ, Sarah L. Booth, Ellen GHM van den Heuvel, Elisabeth Stoecklin, Athanasia Baka, and Cees Vermeer. “The role of menaquinones (vitamin K 2) in human health.” British Journal of Nutrition 110, no. 8 (2013): 1357-1368.
25. Schurgers, Leon J., Kirsten JF Teunissen, Karly Hamulyák, Marjo HJ Knapen, Hogne Vik, and Cees Vermeer. “Vitamin K–containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7.” Blood 109, no. 8 (2007): 3279-3283.
26. Vermeer, Cees Vermeer. “Vitamin K: the effect on health beyond coagulation–an overview.” Food & nutrition research 56, no. 1 (2012): 5329.
27. Vitamin K. University of Maryland Medical Center.

Disclaimer: The content is purely informative and educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.