Vitamin K: Health Benefits, Sources, and Daily Intake

Vitamin K is an essential nutrient that is important for overall health. Without enough vitamin K, serious complications can occur including poor bone development and uncontrollable bleeding. Most individuals get enough vitamin K; however, individuals at risk for certain conditions, such as cardiovascular disease or osteoporosis, may benefit from consuming more of this nutrient through their diet or supplementation. (5)

What is vitamin K?

Vitamin K refers to a family of fat-soluble compounds that are similar in molecular make-up. These compounds facilitate the synthesis of proteins involved in essential functions, including blood clotting (coagulation) and bone metabolism. There are two main types of Vitamin K: K1 and K2. (13)

Did you know? Vitamin K was discovered in 1936 and comes from the German word, koagulation, referring to its blood clotting capacity. (7)

Vitamin K1, also known as phylloquinone, is a product of photosynthesis and is mainly derived from algae and green leafy vegetables. (16) Vitamin K2 includes several compounds called menaquinones (MKs). These compounds differ slightly and are often classified individually as MK-4 through MK-13, according to their molecular structure. (13) MKs are typically produced by bacteria; however, MK-4 is produced from vitamin K1 within the body. All forms of vitamin K function similarly, but vitamin K1 is mainly present in the liver, while vitamin K2 circulates throughout the body. (7) 

Health benefits of vitamin K

Vitamin K is involved in a variety of essential functions throughout the body, including:

• Bone metabolism
• Brain function
• Blood coagulation (clotting)
• Liver function
• Kidney function
• Pancreatic function (7)
  

Research also shows that vitamin K may be protective against certain chronic diseases, potentially due to its role as an antioxidant and anti-inflammatory agent. (7) The following conditions may particularly benefit from vitamin K. 

Cardiovascular disease

Atherosclerosis, a condition characterized by plaque accumulation and calcification (hardening)  in arteries, is one of the leading causes of cardiovascular disease worldwide. (10)(18) Some proteins that counteract plaque accumulation are vitamin K-dependent. Studies indicate that regular high vitamin K intake may attenuate plaque calcification, providing cardioprotective effects. (11)(17)(18)

Coronary (heart) arteries and renal (kidney) arteries appear to benefit the most from vitamin K. As a result, this nutrient may be protective against coronary heart disease and chronic kidney disease (CKD). (7)(15)

Type 2 diabetes 

Type 2 diabetes is a chronic condition characterized by hyperglycemia (high blood sugar), insulin resistance, and dysfunctional insulin secretion. Controlling blood sugar is one of the key ways to manage type 2 diabetes. Vitamin K may support blood sugar regulation by improving insulin sensitivity. (8) Long-term high intake of vitamin K is also associated with a lower risk for developing type 2 diabetes. (3)(12)

Liver disease

The liver is the main site for the synthesis of coagulation factors and inhibitors. Liver disease causes damage to liver tissue, leading to coagulatory dysfunction. (14) Individuals with liver disease tend to experience prolonged bleeding, increasing mortality risk. (2) In patients with advanced liver disease, vitamin K deficiency and lower plasma levels of blood clotting factors and inhibitors were observed. Administration of vitamin K was not found to significantly improve levels of vitamin K or vitamin K-dependent clotting factors. (14) Further research is necessary to understand the relationship between the liver and vitamin K. 

Osteoporosis 

Nutrition is one of the key ways to support bone health, and several studies show that vitamin C, vitamin D, and vitamin K are important nutrients for optimal bone health. Vitamin K2 regulates bone remodeling and strength, reducing the risk of developing a bone fracture in individuals above the age of 50. (7) Low vitamin K intake and low plasma levels of vitamin K are associated with a high risk of bone fractures. Future investigations regarding proper dosages and forms of vitamin K are necessary to fully understand its role in bone support. (6)

Sources of vitamin K

Most North American diets contain an adequate amount of vitamin K. Many foods contain vitamin K, including beans, dairy products, fruits, vegetables, meat, seafood, and poultry. (13) On average, North American adults consume about 20 mcg above the recommended adequate intake of 90 mcg for females and 120 mcg for males. (13) 

Trends indicate that vitamin K intake declines with age, with only one-third of males over 70 years old meeting recommendations. (15) Regularly consuming vitamin K-rich foods and considering vitamin K supplements may be beneficial for some individuals. (7) 

Dietary sources

In North America, spinach and broccoli are among the most common sources of vitamin K1. (13) Good sources of vitamin K2 include fermented foods such as blue cheese, kimchi, and sauerkraut. (4) No toxicity has been reported for vitamin K consumption from food; therefore, there’s no established tolerable upper limit for vitamin K, so eating plenty of these nutrient-rich foods is generally considered safe. (9) 

Did you know? Eating vitamin K foods with a healthy fat source, such as avocado, may help improve vitamin K absorption. (13)

Supplements

Vitamin K is included in many multivitamin supplements, and various forms of vitamin K1 and K2 are also sold as single-ingredient products. (13) Vitamin K1, MK-4, and MK-7 are a few of the most popular vitamin K supplement types. Most studies using vitamin K supplements report no serious adverse effects; however, some individuals indicate experiencing gastrointestinal side effects. (16)(18) If you’re a patient, check with your healthcare provider before adding a new supplement to your regimen. 

Vitamin K precautions

Vitamin K levels can impact coagulation, which may lead to dangerous levels of blood loss. Being an infant, having a malabsorption disorder, or taking certain medications can lead to vitamin K-related complications. (13)

Vitamin K deficiency 

Individuals with vitamin K deficiency can experience excessive bleeding, poor bone development, and an increased risk of cardiovascular disease and osteoporosis. (5) For most, clinically-significant vitamin K deficiency is unlikely; however, select groups have a greater risk. 

Infants during the first few weeks of life are more likely to experience vitamin K deficiency-related bleeding.  (16) Vitamin K deficiency bleeding can be fatal in infants. Fortunately, a single administration of vitamin K1 at birth was discovered to effectively prevent this condition for most newborns. (1) 

For all ages, certain health complications may also lead to vitamin K deficiency. Individuals with malabsorption disorders may not absorb adequate vitamin K. Gastrointestinal conditions such as cystic fibrosis, ulcerative colitis, and short bowel syndrome, may lead to low vitamin K absorption. A high vitamin K diet or vitamin K supplements may be necessary to reach nutritional goals. (13)

Vitamin K medication interactions

Vitamin K may have serious interactions with certain medications, so it’s important to communicate with your healthcare provider before adding vitamin K supplements to your regimen or making changes to your diet. The following medications may impact vitamin K status and lead to health complications:

• Antibiotics
• Anticoagulants (i.e., warfarin, Coumadin)
• Bile acid sequestrants (i.e., cholestyramine, colestipol)
• Orlistat (13)

The bottom line 

Vitamin K is an essential nutrient with an important role in the body, providing an array of health benefits including bone strength and cardioprotection. Try to eat plenty of green leafy vegetables and fermented foods as they are some of the best sources of vitamin K. If you’re considering a vitamin K supplement, be sure to check with your healthcare provider as vitamin K can have potentially dangerous interactions with certain medications.