Do you know one of the functions of vitamin K2 in the human body? Do you know what foods it's found in? Vitamin K2 is not as famous as other vitamins, perhaps because its deficiency is not as common.
It has long been thought that vitamin K2's primary function is to ensure proper blood clotting. Today it is known that this nutrient plays a key role in bone and cardiovascular health. Is it worth taking a vitamin K2 supplement? You will find out throughout this article.
the essentials in brief
- Vitamin K belongs to the group of fat-soluble vitamins. There are two natural forms of vitamin K: phylloquinone K1 and menaquinone K2. It is found in a large number of foods such as fruits and vegetables.
- Vitamin K deficiency is rare but can occur as a result of bariatric surgery, taking a drug that blocks fat absorption, or a medical condition that affects the intestinal absorption of this vitamin.
- The main reason for the lack of knowledge about vitamin K2 is that vitamin K1, the most well-known form of vitamin K, is converted into vitamin K2.
Foods with vitamin K2: What you should know
A sufficient and regular intake of vitamin K2 benefits your health many times over. Your blood vessels and bones in particular benefit from an optimal supply of foods containing vitamin K2.
In order to provide you with comprehensive information about the effectiveness of foods with vitamin K2 and to bring you closer to the current state of science, we have summarized all the important information for you in the following sections.
What is vitamin K?
Vitamin K is a fat-soluble or fat-soluble vitamin. It is a very important nutrient that our body needs for blood clotting, bone health and other bodily functions(1,2,3">.
Which vitamins belong to the vitamin K group?
Vitamin K is a lipophilic vitamin, meaning it is soluble in lipids, and we have three different types of vitamin K:
- Phylloquinone Vitamin K1: Vitamin K1 is found in green leafy vegetables, it accounts for 70 to 90% of total vitamin K.
- Menaquinone-Vitamin K2: Is the result of the conversion of vitamin K1 by intestinal bacteroids and bifidobacteria and activates proteins that regulate the fate of calcium, helping to fix it in the bones.
- Menadione Vitamin K3: Vitamin K3 is synthetic. It was incidentally known around 1920, studies showed that animals that suffered a lot of bleeding were also deficient in vitamin K.
As already mentioned, the main function of vitamin K is very much involved in the role of blood clotting. Consequently in heart and bone health(4).
Foods of plant origin are very good sources, especially green vegetables. They supply the variant vitamin K1. (Image Source: MabelAmber / pixabay)
However, it is known that only a small part of vitamin K1 is converted into K2 and that this is essential for healthy bones, the circulatory system or the nervous system.
The half-life of vitamin K2 in the blood is much longer than that of vitamin K1, making it more effective. Vitamin K1 is transported and used in the liver.
What are the effects of vitamin K2?
Researchers are still studying vitamin K2 to determine how it affects health. Here are some examples of the results of this research:
Coronary heart disease
Scientists are studying whether levels of vitamin K2 in the blood increase the risk of heart disease, possibly by causing the blood vessels leading to the heart to become stiffer and narrower. More research is needed to understand whether vitamin K2 supplements help prevent heart disease(2,5,6">.
osteoporosis
Vitamin K2 is important for healthy bones. Studies show that people who eat more foods rich in vitamin K2 have stronger bones and are less likely to break their hips than people who eat less of these foods(5,4,3">.
Some studies have found that taking vitamin K2 supplements improves bone strength and the likelihood of fracture, but other studies have not come to the same conclusion.
More studies are needed to better determine whether vitamin K2 supplements improve bone health and reduce the risk of osteoporosis(7.8">.
What functions does vitamin K2 have?
One of the most important functions identified for vitamin K2 was its crucial role in blood clotting. Today, vitamin K2 has been shown to be an essential micronutrient for maintaining bone and cardiovascular health.
The following are the main functions of vitamin K2:
blood coagulation and protein synthesis
The role of vitamin K2 is essential in blood coagulation, the synthesis of proteins found in plasma, kidneys and bones. In addition, it is important for the prevention of heart disease. A lack of vitamin K2 promotes diseases such as dental caries, osteoporosis, varicose veins or infectious diseases(4.3">.
hardening of the arteries
This vitamin helps prevent hardening of the arteries, a common factor in heart disease. Scientists suggest that the vitamin may help prevent calcium build-up in the lining of arteries and other body tissues(2,5,6">.
Vitamin K2 helps the body build healthy bones and tissues through protein.
insulin sensitivity
Vitamin K2 improves insulin sensitivity. People who take prescription vitamin K2 supplements are less likely to develop type 2 diabetes. Vitamin K2 also has antioxidant properties, meaning it works with the immune system to prevent oxidative damage to our cells(9).
bone health
Vitamin K2 supports bone health, it's not just about taking calcium, this vitamin acts like a biological "glue" that helps to fix calcium. Studies have been conducted showing the protective effects of this vitamin against osteoporosis(5,4,7,10">.
Which foods contain vitamin K2?
Vitamin K is abundant in many fruits and vegetables, especially greens(3). The foods that are the richest in vitamin K include sun-dried tomatoes, celery, okra, cranberries, dried sage, kale, collards, blueberries, spinach, broccoli, green onions, Brussels sprouts, and others that we will mention below.
There is no recommendation for vitamin K2 as it is expected to be produced by the gut flora.
There are some foods that provide vitamin K2 directly. This is found, for example, in whole milk products and in the fat of grass-fed animals.
However, it is also found in fermented vegetables such as soybean curd, which contains up to 900 micrograms in 100 grams. Sauerkraut provides about 4-5 micrograms.
The best strategy for increasing your vitamin K2 intake is to eat plenty of fruits and vegetables every day, as they contain vitamin K1, which is converted to K2 by digestive bacteria.
Foods richer in vitamin K1:
broccoli
When consumed regularly, broccoli contributes to nervous system, eye, heart, bone, blood pressure, and skin health. It is also a very powerful food to boost your immune system.
Vitamin K2 deficiency occurs very rarely in a healthy and balanced diet. Because most foods contain so much vitamin K that you can easily cover your recommended daily amount. (Image source: Saurav Rastigi / unsplash)
Adding more broccoli to your diet can help you meet your daily zinc, calcium, potassium, vitamin C, and vitamin K needs. Just half a cup provides more than the recommended daily amount of vitamin K.
Serving Size: 1/2 cup, 110.06 micrograms of Vitamin K (138% of the Daily Value).
spinach
One of the healthiest foods to add to your diet is spinach. Whether raw or cooked, spinach is a unique source of various vitamins, minerals, and antioxidants, including vitamin C, iron, calcium, and vitamin K.
If you're not sure how to add more spinach to your diet, start by using it as a base for your salads, sautéing it with olive oil and garlic, adding it to your pizza as a topping, or grinding it and cook it in your favorite pasta sauce.
Serving Size: 1 cup, 144.87 micrograms of Vitamin K (181% of the Daily Value).
raspberries
Raspberries are high in vitamins and minerals, including vitamin K, so they can be an essential part of your daily diet.
Many other types of berries contain similar benefits. So make it a habit to add them to a fruit salad or shake for breakfast, lunch or a snack and give your mind and body a nutritional boost.
Serving Size: 1 cup, 9.59 micrograms of Vitamin K (12% of the Daily Value).
carrots
A medium-sized carrot provides more than eight micrograms of vitamin K, enough to help you meet 10% of your recommended daily value.
That same carrot adds only 25 calories to your diet, and the wealth of other vitamins and minerals makes carrots a great food to enjoy on a regular basis.
asparagus
There are many reasons to put more asparagus on the menu. It has anti-aging properties, may help prevent Alzheimer's disease and is rich in antioxidants that protect against free radicals and certain types of cancer.
They are also rich in many vitamins and minerals that our bodies need to stay healthy. These include vitamin A, vitamin C, folic acid, fiber, vitamin E and vitamin K.
Serving Size: 4 units, 48 micrograms of vitamin K (60% of the daily value).
chili powder
If you use chili powder more often in your cooking, you will receive the benefits of vitamin A, vitamin C, potassium, phosphorus, calcium, manganese, zinc and selenium.
If vitamin K is a problem in your diet, chili powder is a great source; just one spoonful of this bright red spice contains 11% of the recommended daily value.
gherkins
Pickles contain small amounts of a number of vitamins and minerals. An average pickle contains 34% of the recommended daily value.
Pickles are also a good source of fiber and contain a small but useful source of antioxidants like vitamin A and lutein.
blackberries
Rich and dark in color, blackberries contain many antioxidants found within. In addition, they are rich in minerals such as copper and manganese, as well as vitamins such as vitamin C and vitamin K.
A cup of these juicy berries contains 36% of the vitamin K the average adult should be consuming per day.
cabbage
Raw or steamed cabbage is a food that helps treat high cholesterol, stomach ulcers, arthritis, weight gain, and constipation. A cup of chopped cabbage contains 76 micrograms of vitamin K, which is almost 100% of the recommended daily value.
Eating more cabbage increases your intake of vitamin K, vitamin C, fiber, vitamin E, calcium, magnesium, and potassium.
Kale
If you're not used to eating kale as a side dish, make a change and give it a place with some of your favorite foods.
A cup of chopped kale provides your body with almost 700% of the total recommended daily intake of vitamin K. It is also rich in other vitamins such as A and C, as well as iron and calcium, which are very beneficial to your health.
Dried Sage
Many people use dried herbs to spice up their cooking from time to time, but not everyone is aware of the many health benefits they can offer.
Dried sage is a great source of vitamin K, and one tablespoon provides 43% of the recommended daily amount. For additional benefits, such as antioxidants and anti-inflammatory agents, consider adding dried sage to your cooking.
okra
Half a cup of okra slices provides 34 micrograms of vitamin K in your diet, which is about 43% of your daily recommended intake. If you're not sure how to get more vitamin K from this vegetable, try serving it with tomato soup, corn, rice, or shrimp.
blueberries
Blueberries are a very healthy food to add to your diet. They are full of fiber, potassium, iron, copper, zinc and various antioxidants.
To get more vitamin K into your diet, enjoy a cup of blueberries each day and you'll get 36% of the recommended daily value.
For some ideas, we recommend adding blueberries to yogurt, salad or oatmeal for a healthy and tasty snack.
celery
Celery is a bold flavored vegetable that's easy to prepare when you want a quick healthy snack. Celery can be eaten as a snack along with hummus or nut butters. It also tastes very good in salads, especially in sweet and sour ones.
An average celery stalk provides 15% of the recommended intake of vitamin K and is also a great source of folate, antioxidants, calcium and potassium. And at just 6 calories per stalk, you can enjoy it in abundance without worrying about calorie intake.
Sun-dried tomatoes
Sun-dried tomatoes are an excellent ingredient for salads, sauces, pasta dishes, sandwiches and pizza. There are many ways to enjoy them, so start experimenting and try to find a way to best incorporate this healthy vegetable into your diet.
Sun-dried tomatoes can be soaked and then used in a variety of ways. A cup of sun-dried tomatoes contains 29% of the recommended daily amount of vitamin K. They are also a great source of lycopene, vitamin A, vitamin C, calcium and iron.
How much vitamin K is useful per day?
The amount of vitamin K needed depends on age and gender. The average daily amounts, expressed in micrograms (mcg), are as follows:
| life stage | Recommended dose |
|---|---|
| Infants up to 6 months | 20 mcg |
| 1 to 3 years old | 30 mcg |
| 4 to 8 years old | 55 mcg |
| 9 to 13 years old | 60 mcg |
| 14 to 18 years old | 75 mcg |
| Adult males over 19 years old | 120 mcg |
| Adult females over 19 years old | 90 mcg |
| Pregnant or breastfeeding teenagers | 75 mcg |
| Pregnant or lactating women | 90 mcg |
What happens with vitamin K deficiency?
The main symptom of vitamin K1 deficiency is the tendency to bleed and bruise, as well as blood spots under the nails.
Early and deep wrinkles on the face and neck can be a symptom of vitamin K2 deficiency and a risk for developing osteoporosis, according to a study published in Endocrine Reviews(5,4,8,6">.
Vitamin K deficiency is rare. Most people usually get enough vitamin K through the food they eat.
In addition, bacteria in the large intestine produce a certain amount of vitamin K, which is absorbed by the body.
However, some people may have trouble getting enough vitamin K due to certain health conditions:
- People who have undergone bariatric surgery.
- People who decrease the amount of vitamin K their body absorbs because they may have one of the following conditions: short bowel syndrome, cystic fibrosis, celiac disease, or colitis.
- Newborns who have not yet received a vitamin K vaccine.
What happens if you overdose on vitamin K?
There are not many studies evaluating vitamin K toxicity, and hypervitaminosis levels cannot be reached by diet alone(5).
The consequences could occur after supplementation if it is administered in very high doses and triggers hypervitaminosis. The effects can be:
- liver problems
- Hemolytic anemia
- Neurological diseases in infants
- Interference with some antioxidants
- Irregular blood clotting
- Jaundice in the skin and eyes from excess bilirubin
Therefore, we recommend consulting your doctor before taking any supplements so you can confirm if you have any health issues related to this micronutrient.
Why take vitamin K2 with vitamin D3?
According to the researchers, there could be a significant synergy between vitamins D3 and K2. Some in vitro studies suggest that vitamin D3 has a positive impact on certain vitamin K2-dependent bone proteins by increasing their levels to induce bone formation(4).
The combination of vitamin D3 and K2 is ideal for promoting bone health.
Animal and human studies further support these findings by showing that taking vitamin D3 and vitamin K2 together has a greater effect than taking vitamin K2 alone. Taking vitamins D3 and K2 with calcium also has a greater effect than taking calcium alone, especially when it comes to bone health.
What alternatives are there to vitamin K?
Our ability to enjoy an energetic and healthy life depends heavily on our eating habits and daily activity level. For healthy blood circulation, taking vitamin K is ideal as it provides us with the nutrients that help our blood to clot(2.5">.
Regardless of whether we have a vitamin K deficiency or whether we want to supplement our diet with the necessary amount of vitamins, we have the option of taking vitamin K supplements.
Vitamin K supplements are marketed in capsule, powder, or liquid solution form. In order to purchase a suitable product, it is important to evaluate the type of vitamin K, added ingredients, suitability for vegans, and quality certifications.
Conclusion
A sufficient content of vitamin K2 is very important for many bodily processes, eg for maintaining the flexibility of the blood vessels, for strengthening the bones, for blood clotting and for protecting the heart. Although vitamin K deficiency is rare, some medical conditions and medications can affect its absorption.
Most foods are high in vitamin K1, which converts to vitamin K2, making it easy to meet your recommended daily intake. It is mainly found in green leafy vegetables. Green cabbage, spinach, lamb's lettuce or chard are therefore good suppliers. Other types of fruit and vegetables also contain comparatively large amounts of vitamin K.
References
- Bruce Furie, Beth A Bouchard, Barbara C Furie. Vitamin K-Dependent Biosynthesis of γ-Carboxyglutamic Acid, Mar 1999, Volume 93, Issue 6
- Martin J. Shearer 1, Paul Newman 2. Metabolism and cell biology of vitamin K, 2008, Epithelial Cell Biology Laboratory, Cancer Research UK, Cambridge Research Institute, Cambridge
- Maya KAMAO, Yoshitomo SUHARA, Naoko TSUGAWA, Masako UWANO, Noriko YAMAGUCHI, Kazuhiro UENISHI, Hiromi ISHIDA, Satoshi SASAKI, Toshio OKANO. Vitamin K Content of Foods and Dietary Vitamin K Intake in Japanese Young Women, 2007, Journal of Nutritional Science and Vitaminology, Doi.org/10.3177/jnsv.53.464
- Diane Feskanich, Peter Weber, Walter C Willett, Helaine Rockett, Sarah L Booth, Graham A Colditz. Vitamin K intake and hip fractures in women: a prospective study, Jan 1999, The American Journal of Clinical Nutrition, Volume 69, Issue 1, Pages 74-79, Doi.org/10.1093/ajcn/69.1.74
- Ellen CM Cranenburg, Leon J Schurgers, Cees Vermeer. Vitamin K: The coagulation vitamin that became omnipotent, Thromb Haemost 2007; 98(01): 120-125, DOI: 10.1160/TH07-04-0266
- Ralf Westenfeld MD 1, Thilo Krueger MD 2, Georg Schlieper MD 2, Ellen CM Cranenburg MD & PhD 3, Elke J. Magdeleyns BSc 3, Stephan Heidenreich MD 4, Stefan Holzmann MD 5, Cees Vermeer PhD 3, Willi Jahnen-Dechent PhD 6, Markus Ketteler MD 7, Jürgen Floege MD 2, Leon J. Schurgers PhD 8. Effect of Vitamin K2 Supplementation on Functional Vitamin K Deficiency in Hemodialysis Patients: A Randomized Trial, Feb. 2012, American Journal of Kidney Diseases, Volume 59, Issue 2, Doi.org/10.1053/j.ajkd.2011.10.041Pages 186-195
- Sarah L Booth, Katherine L Tucker, Honglei Chen, Marian T Hannan, David R Gagnon, L Adrienne Cupples, Peter WF Wilson, Jose Ordovas, Ernst J Schaefer, Bess Dawson-Hughes, Douglas P Kiel. Dietary vitamin K intakes are associated with hip fracture but not with bone mineral density in elderly men and women, May 2000, The American Journal of Clinical Nutrition, Volume 71, Issue 5, Pages 1201-1208, Doi.org/10.1093/ajcn/ 71.5.1201
- Devyani Misra, Sarah L Booth, Irina Tolstykh, David T Felson, Michael C Nevitt, Cora E Lewis, James Torner, Tuhina Neogi.Vitamin K Deficiency Is Associated with Incident Knee Osteoarthritis , Mar. 2013, The American Journal of Medicine, Volume 126, Issue 3, Pages 243-248, Doi.org/10.1016/j.amjmed.2012.10.011
- Lily MT Vervoort, Jacintha E Ronden, Henk HW Thijssen. The potent antioxidant activity of the vitamin K cycle in microsomal lipid peroxidation, Oct. 1997, Biochemical Pharmacology, Volume 54, Issue 8, Pages 871-876, Doi.org/10.1016/S0006-2952(97)00254-2
- Nicolaidou P, Stavrinadis I, Loukou I et al. The effect of vitamin K supplementation on biochemical markers of bone formation in children and adolescents with cystic fibrosis. Eur J Pediatr 165, 540-545 (2006). Doi.org/10.1007/s00431-006-0132-1