Vitamin K In Strawberries For Blood Clotting

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Our blood is crucial in our body as it provides nutrients, such as oxygen to our cells and tissues, allowing them to survive. The human body protects against blood loss by clotting. Too much blood loss can result in death, due to blood being critical in providing nutrients to our cells. Platelets, coagulation factors and proteins are a few of the substances that have a key role in blood clotting.1 However, this article will focus on the importance of vitamin K in blood clotting.

Vitamin K in blood clotting

Vitamin K is crucial in the process of blood clotting. Blood clotting occurs when a blood vessel is damaged and stops too much blood being lost from the body. Severe blood loss can be fatal to us. Vitamin K is needed to make proteins, such as prothrombin, which are needed in the blood clotting process.2

Understanding blood clotting

Blood clotting in our body begins when chemical signals are sent from the blood vessel which is injured, causing the blood vessel to narrow. The narrowing of the blood vessels helps to prevent lots of blood from being lost. Chemical signals are sent to our spleen, this is where platelets are stored. Platelets have a key role in our blood clotting. As a result, platelets are released into our blood and flow towards the site of the injury. Where the injury was sustained to our blood vessel the walls of this blood vessel become sticky, this allows platelets to be caught at the injury site as they flow past in our blood. The platelets will start to change shape and become stickier, allowing the platelets to clump together within our blood vessels, forming a platelet plug. The platelets in our blood release molecules which turn on clotting factors. One very important clotting factor is fibrin, which helps hold the platelet plug in place in the blood vessel, where the injury has been sustained. This forms a fibrin clot. The platelets will begin to contract to pull the two sides of the blood vessel that has been injured closer together, this makes the repair process easier (National Heart, Lung and Blood Institute).

Role of vitamin K

Vitamin K is a nutrient that was discovered in 1929. There are two different forms of vitamin K: K1 and K2, which are sourced from different foods. K1 is found in plant foods, whereas K2 is found in animal and fermented foods 

Importance of vitamin K in blood clotting

Vitamin K is needed to produce prothrombin, which is a key protein in the blood clotting process in our bodies.2

How vitamin K supports the clotting process

Prothrombin is a protein that is directly involved in the blood clotting process. However, vitamin K is needed to produce prothrombin in our body. If there is no vitamin K, there is no prothrombin. As a result, prothrombin cannot be converted into thrombin. Thrombin is an enzyme in our blood which cleaves the soluble protein fibrinogen to form an insoluble protein known as fibrin. Fibrin is needed to create stabilized cross-links in the blood clot. Ultimately, fibrin defines how strong a blood clot is.3

Sources of vitamin K

Vitamin K exists as both K1 and K2, with K1 being the most common form of the vitamin, and this can be found in green leafy vegetables.

Natural dietary sources of vitamin K

There are foods that are naturally high in vitamin K, and these include the following 

  • Collard greens
  • Raw kale
  • Raw spinach
  • Cooked broccoli
  • Dry roasted cashew nuts
  • Carrot juice
  • Blueberries
  • Grapes
  • Olive oil
  • Pomegranate juice

How much vitamin K do I need a day?

You should be taking 1 milligram of vitamin K for every 1 kg of your body weight, daily. For example, if you weigh 70kg you would need 70 milligrams of vitamin K per day.

Importance of a balanced diet for vitamin K intake

Vitamin K1 is important for blood clotting and is sourced mainly from green leafy vegetables, such as kale and broccoli, with approximately 75-90% of the vitamin K we need in our body being vitamin K1. Vitamin K2 is also important for blood clotting but is found in certain animals and fermented foods. Therefore, a balanced diet is needed to make sure we are absorbing both vitamin K1 and vitamin K2 as they are both needed for blood clotting.

Vitamin K content in strawberries

One strawberry contains approximately 3 micrograms (mcg) of vitamin K.

This is more compared to other fruits, such as watermelons, bananas and pineapples, which all contain less than 1.5 mcg of Vitamin K. Compared to leafy greens such as kale, which contain  565 mcg of vitamin K per half a cup, when it is cooked this amount is very low.

Deficiency and excess of vitamin K

Vitamin K deficiency can occur when we are not receiving the required amount of vitamin K in our diet, or health conditions such as liver disease, cystic fibrosis, or alcoholism. Enteric diseases may also mean that vitamin K is not absorbed by our body too. Vitamin K deficiency can result in an increased risk of bone fractures.4 There is also a risk of osteoporosis as vitamin K has a key role in our body in keeping our bones healthy.

Other symptoms of vitamin K deficiency are excessive bleeding, blood clots underneath the nails, as well bruising easily. If you are diagnosed with vitamin K deficiency the treatment is usually the oral delivery of a drug called phytonadione, which is vitamin K1. However, this may also be delivered via an injection.

Certain individuals are at higher risk of having vitamin K deficiency, which includes the following

  • Individuals who have had weight loss surgery
  • Newborns who don’t get a vitamin K injection after their birth
  • Individuals with cystic fibrosis and coeliac disease
  • Individuals with short bowel syndrome

There is not enough evidence to confirm what will happen if excess vitamin K is taken.

Vitamin K and its interaction with certain medications

Antibiotics kill bacteria that are present in our gut and produce vitamin K. If you are on a course of antibiotics you may also have to take vitamin K supplements if your vitamin K intake is very low. A certain group of drugs known as anticoagulants, which stop blood clotting, can reduce the amount of vitamin K-dependent clotting factors. If you take an anticoagulant medication you are advised to keep your vitamin K intake consistent.  An over-the-counter medication known as Orlistat is used for weight loss, and works by reducing fat absorption. However, as vitamin K is a fat-soluble vitamin this could reduce how much vitamin K is being absorbed by your body and result in vitamin K deficiency. It is advised to take a multivitamin, which contains vitamin K, in conjunction with this medication. Bile acid sequestrants are used to lower blood cholesterol levels, and may also affect how much vitamin K is absorbed by the body.

Vitamin K supplements

You may be advised to take vitamin K supplements if you are taking another medication which may affect your absorption of vitamin K in the body, such as anticoagulants or Orlistat. However, it is important to note that it is not advised that you should need additional supplements of vitamin K in your diet if there is not a medical reason behind this.

It is important to check that vitamin K supplements to not interact with other types of medication you are taking before you start the supplements. This is due to the risk of potential side effects from vitamin K and drug interactions.


Vitamin K is important for blood clotting as it is needed to produce prothrombin, which is needed in the blood clotting process

Vitamin K has the subtypes K1 and K2

Vitamin K1 can be found in green, leafy vegetables

Vitamin K2 can be found in animal and fermented foods

Both vitamins K1 and K2 have roles in blood clotting

Certain medications interact with vitamin K

Vitamin K deficiency can lead to bone fractures, bruising and excessive bleeding

The effects of excessive vitamin K intake are currently not known

The vitamin K content in strawberries is low compared to leafy green vegetables, such as kale


  1. Garmo C, Bajwa T, Burns B. Physiology, clotting mechanism. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Nov 2]. Available from:
  2. Stępień A, Koziarska-Rościszewska M, Rysz J, Stępień M. Biological role of vitamin k—with particular emphasis on cardiovascular and renal aspects. Nutrients [Internet]. 2022 Jan 8 [cited 2023 Nov 2];14(2):262. Available from:
  3. Palta S, Saroa R, Palta A. Overview of the coagulation system. Indian J Anaesth [Internet]. 2014 [cited 2023 Nov 3];58(5):515–23. Available from:
  4. Rodríguez-Olleros Rodríguez C, Díaz Curiel M. Vitamin k and bone health: a review on the effects of vitamin k deficiency and supplementation and the effect of non-vitamin k antagonist oral anticoagulants on different bone parameters. J Osteoporos [Internet]. 2019 Dec 31 [cited 2023 Nov 3];2019:2069176. Available from:

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Alisha Solanki

BSc Biomedicine, Lancaster University

Current biomedical science student with a keen interest in medical communications. I have a passion for producing scientifically correct articles in plain language, and communicating advances in the biomedical field to the public. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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