Role of Vitamin K

Vitamin K refers to a group of fat-soluble vitamins similar in chemical structure. Vitamin K is critical for blood function acting as coenzymes which play an essential role in blood coagulation (aka blood clotting). Blood-clotting proteins are continuously circulating in the blood. Upon injury to a blood vessel, platelets stick to the wound forming a plug. Without vitamin K, blood would not clot.

Vitamin K is also required for maintaining bone health. It modifies the protein osteocalcin, which is involved in the bone remodeling process. All the functions of osteocalcin and other vitamin K-dependent proteins in bone tissue are not well understood and are under further investigation. Some studies do show that people who have diets low in vitamin K also have an increased risk of bone fractures.

Dietary Reference Intake for Vitamin K

The AI of vitamin K for adult females is 90 micrograms per day, and for males, it is 120 micrograms per day.

Dietary Sources of Vitamin K

Vitamin K is present in many foods. It is found at the highest concentrations in green vegetables such as broccoli, cabbage, kale, parsley, spinach, and lettuce. Additionally, vitamin K can be synthesized via bacteria in the large intestine. The exact amount of vitamin K synthesized by bacteria that is actually absorbed in the lower intestine is not known but likely contributes less than 10 percent of the recommended intake. Newborns have low vitamin K stores and it takes time for the sterile newborn gut to acquire the good bacteria it needs to produce vitamin K. As a result, it has become a routine practice to inject newborns with a single intramuscular dose of vitamin K. This practice has basically eliminated vitamin K-dependent bleeding disorders in babies.

Consuming Too Little Vitamin K

A deficiency in vitamin K causes bleeding disorders. It is relatively rare, but people who have liver or pancreatic disease, celiac disease, or malabsorption conditions are at higher risk for vitamin K deficiency. Also, prolonged use of antibiotics may play a role in vitamin K deficiency as they reduce bacterial populations in the large intestine. Signs and symptoms include nosebleeds, easy bruising, broken blood vessels, bleeding gums, and heavy menstrual bleeding in women. While there is some evidence to suggest that vitamin K consumption is related to bone fractures in women, there is not enough evidence to suggest that it causes osteoporosis.

Taking into account age-related considerations is crucial for understanding the impact of vitamin K deficiency and bleeding disorders across different stages of life. While the text mentions the importance of newborns receiving a vitamin K injection, it is also relevant to highlight the vulnerability of older adults to vitamin K deficiency. Age-related factors, such as changes in nutrient absorption and medication use, can increase the risk of vitamin K deficiency and other associated bleeding disorders in older adults.

Consuming Too Much Vitamin K

A UL for vitamin K has not been set. There is no UL for vitamin K because it has a low potential for toxicity. No adverse effects associated with vitamin K consumption from food or supplements have been reported in humans or animals. The function of the anticoagulant drug warfarin is impaired by excess vitamin K intake from supplements.