Sources of Vitamin K

Vitamin K is a group of fat-soluble vitamins involved in the synthesis of proteins needed for blood coagulation and for calcium binding in bones and other tissues.

Chemically, the vitamin K family is made up of 2-methyl-1 derivatives. Two natural forms of Vitamin K exist, namely Vitamin K1 and Vitamin K2. Vitamin K1 is also called phylloquinone, phytomenadione or phytonadione and is synthesized in plants, particularly green, leafy vegetables, because it is involved in photosynthesis. Vitamin K1 is also abundant in various fruits such as avocado and kiwi fruit and some herbs contain very high amounts of vitamin K. For example, two tablespoons of parsley is known to contain more than 150% of the recommended daily amount of vitamin K.

Vitamin K2, which is the main form stored in animals, has is a number of subtypes referred to as menaquinones, homologues of the vitamin that are characterized by the different lengths of their isoprenoid side chains. Bacteria in the large intestine can convert vitamin K1 into vitamin K2 , as well as being able to lengthen the isoprenoid side chains of vitamin K2, to give a range of vitamin K2 homologues.

There are also three synthetic forms of vitamin K, which are vitamins K3, K4, and K5, although vitamin K3 has shown toxic effects in some studies.

As a fat-soluble vitamin, absorption of vitamin K1 is often greater in the presence of butter or oil. The tight binding of vitamin K1 to thylakoid membranes in chloroplasts means its bioavailability is poor unless fats are added. The bioavailability of vitamin K is 5% in cooked spinach, for example, whereas adding fat to the spinach increases the bioavailability to 13%.

According to the U.S. Dietary Reference Intake, the intake of vitamin K a 25 year old man requires each day is 120 micrograms. For a woman, the amount would be 90 micrograms/day; for infants 10–20 micrograms/day and for children and teenagers, the daily requirement would be 15–100 micrograms/day.

Although it is possible to have an allergic reaction to vitamin K supplementation, there is no known risk of vitamin K1 or vitamin K2 having toxic effects and no tolerable upper intake level has therefore been set.

Newborn babies are at risk of vitamin K deficiency because they do not possess the gut bacteria required to help synthesise this vitamin. Furthermore, vitamin K does not cross the placenta to reach the fetus during pregnancy and human milk is low in this vitamin, meaning breast feeding does not supply adequate amounts to the newborn.

Breast-fed babies can be low in vitamin K for several weeks until their guts start to develop the bacteria required to synthesize vitamin K2. These babies are at risk of a condition called hemorrhagic disease of the newborn, which can lead to severe bleeding that sometimes causes brain damage. As a preventative measure, babies are routinely given vitamin K injections after birth. Infant formula is made to contain vitamin K, but even formula-fed babies may be low in vitamin K for a few days.

Further Reading

Last Updated: Jun 21, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Mandal, Ananya. (2023, June 21). Sources of Vitamin K. News-Medical. Retrieved on October 31, 2024 from https://www.news-medical.net/health/Sources-of-Vitamin-K.aspx.

  • MLA

    Mandal, Ananya. "Sources of Vitamin K". News-Medical. 31 October 2024. <https://www.news-medical.net/health/Sources-of-Vitamin-K.aspx>.

  • Chicago

    Mandal, Ananya. "Sources of Vitamin K". News-Medical. https://www.news-medical.net/health/Sources-of-Vitamin-K.aspx. (accessed October 31, 2024).

  • Harvard

    Mandal, Ananya. 2023. Sources of Vitamin K. News-Medical, viewed 31 October 2024, https://www.news-medical.net/health/Sources-of-Vitamin-K.aspx.

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
Post

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
New pro-oxidant supplement shows promise in slowing prostate cancer progression