Vitamin K is a nutrient essential to life. It participates in many important functions of the body, such as blood clotting and bone health.
What is Vitamin K?
It is an essential liposoluble vitamin, which requires fat in order to be absorbed by the body. The term vitamin K refers to a group of molecules of similar chemical structure and action. In its natural form, it is present in a wide variety of foods as well as in dietary supplements.
What forms of Vitamin K exist?
It is categorized into two forms, vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Vitamin K1 is mainly found in plant sources such as green leafy vegetables (spinach, broccoli, lettuce, etc.), in vegetable oils as well as in some fruits (blueberries, figs, etc.).
In contrast, vitamin K2 is of microbial origin, as it can be produced by intestinal bacteria. In nature, menaquinone is present in moderate amounts in animal products, such as meat, milk, soy or eggs, as well as in fermented products such as traditional food Natto.
Although both types of vitamin K are equally beneficial to health, vitamin K2 (menaquinone) seems to have greater activity and bioavailability.
Deficiency of Vitamin K
The lack of vitamin K is relatively rare. If there are low levels, there are major health problems such as bleeding, bruising, reduction of bone density and increased risk of osteoporosis. People with increased risk for vitamin K deficiency are those who have/are:
- inflammatory bowel diseases (e.g., ulcerative colitis)
- malabsorption syndrome (eg short bowel syndrome or after bariatric surgery)
- poor diet
- liver disease
- cystic fibrosis or celiac disease
- newborns and premature infants who breastfeed
- under long-term antibiotic treatment
What are the effects of vitamin K?
Vitamin K acts as a coenzyme in many biochemical reactions of the organism as well as in the synthesis and proper function of various proteins, such as prothrombin and osteocalcin.
Vitamin K helps in blood clotting, in stopping bleeding, reduces faster wound healing and prevents bruising. The blood clotting process is a particularly complex. Many of the proteins involved in clotting need vitamin K for their proper action. Without the required amount of vitamin K, there is an increased risk of bleeding.
One of the main causes of heart attack is calcium deposition in the arteries. The calcification of the arteries makes them stiffer and narrow, with reduced elasticity. Taking vitamin K prevents the deposition of calcium in the vessels and tissues. However, larger and better-designed studies are needed to elucidate the role of vitamin K in cardiovascular disease prevention.
Osteocalcin is a vitamin K-dependent hormone, which is responsible for bone health and deposition of calcium in the bones. In particular, vitamin K helps the calcium that circulates in the blood to be stored in the bones. Studies suggest that people who consume large amounts of vitamin K through food or dietary supplements have stronger bones and are less likely to suffer a bone fracture. The aforementioned effect of vitamin K was also observed in people with osteoporosis. The action of vitamin K is enhanced by vitamin D.
Brain health and inflammation
It is now established that chronic diseased such as Alzheimer’s disease, cancer, Parkinson’s disease and heart failure are inflammatory conditions. In recent years, more and more studies have shown that vitamin K has anti-inflammatory properties, protecting the brain cells from oxidative stress and the harmful effects of free radicals.
Nutritional supplements with vitamin K
Vitamin K is available either in dietary supplements or in formulas with calcium, magnesium and/or vitamin D. The most common forms of vitamin K in food supplements are synthetic and are either vitamin K1, phylloquinone and phytonadione, as well as vitamin K2, menaquinone-4 (MK-4) and menaquinone-7 (MK-7), which are the most studied forms. Studies suggest that vitamin K2 supplements in the form of MK-7 have greater bioavailability and time of action.
How much Vitamin K do I need?
The needs vary according to the stage of development and gender. For men, the daily requirement for vitamin K is 120 mcg while for women 90 mcg. The therapeutic dosage ranges from 50-150 mcg.
Are there any interactions and contraindications with vitamin K?
Supplementation of vitamin K in healthy individuals is safe. However, people who take anticoagulants should receive a certain amount of vitamin K per day, through both food and supplements, as there is an increased risk of a bleeding episode.
Additionally, people who take antibiotics, orlistat or bile acid sequestrants may have increased needs of vitamin K, as they either reduce the production of vitamin K by the intestinal bacteria or the absorption of vitamin K by the body.