Vitamin K is a vitamin that is mainly found in green leafy vegetables, broccoli and Brussels sprouts.

Vitamin K is most commonly used for blood clotting problems, and its intake must be controlled in the case of anticoagulant medication because it affects the treatment and should not be taken in combination with warfarin, coumarin anticoagulants. Vitamin K is also used to prevent coagulation problems in neonates that do not have enough vitamin K but also to prevent vitamin K deficiency.

Increased understanding of the role of vitamin K in the body beyond blood coagulation has led some researchers to suggest that the recommended amounts for vitamin K diet should be increased. In 2001, the National Institute of Medical Food and Nutrition increased the recommended amounts of vitamin K slightly.

Vitamin K is effective for:
  • Prevention of bleeding problems in neonates with low levels of vitamin K (hemorrhagic disease).
  • Treatment and prevention of bleeding problems in people with low levels of blood coagulation protein (prothrombin).
  • In a hereditary hemorrhagic disorder called Vitamin K Dependent Deficiency Factor (VKCFD). Taking vitamin K orally or as an injection into the vein can help prevent bleeding in people with VKCFD.
  • Reversing the effects of overdose of warfarin used to prevent blood clotting.
Possibly effective for:
  • Weak bones (osteoporosis). Taking a certain form of vitamin K2 appears to improve bone strength and reduce the risk of fracture in most elderly women with weak bones. Taking vitamin K1 seems to increase bone strength and can prevent fractures in older women. Vitamin K1 does not appear to improve bone strength in women who have not gone through menopause or in people with Crohn's disease.
Possibly ineffective for:
  • Bleeding in areas of the brain fluid (intra-abdominal bleeding). Providing vitamin K to women at risk of premature birth does not seem to prevent bleeding in the brains of infants. It also does not seem to reduce the risk of nerve damage caused by these bleeds.
Insufficient evidence to rate effectiveness for:
  • Blood disorder (β-thalassemia). Research shows that taking vitamin K2 orally along with calcium and vitamin D can improve the bone mass in children with this blood disorder.
  • Breast cancer. Studies show that higher dietary intake of vitamin K2 is associated with a lower risk of developing breast cancer.
  • Cancer. Some studies have linked a higher intake of vitamin K2, but not vitamin K1, with a reduced risk of death from cancer. But another research has linked a higher vitamin K1 intake, but not vitamin K2, with a reduced risk of death from cancer.
  • Colorectal cancer. Early studies show that higher dietary intake of vitamin K is not associated with reduced risk of colon and rectal cancer.
  • Lung cancer. Early studies show that higher vitamin K2 intake from food is associated with a reduced risk of lung cancer and death associated with lung cancer. The nutritional intake of vitamin K1 does not seem to be associated with a reduced risk of these events.
  • Heart disease. Higher dietary intake of vitamin K2 has been associated with a reduced risk of heart disease, risk factors for heart disease and death due to heart disease in elderly men and women, but vitamin K2 intake from food does not seem to be associated with a reduced risk of heart disease in people high risk for this condition. Nutritional uptake of vitamin K1 is not associated with a reduced risk of heart disease. However, increased vitamin K1 intake from food has been associated with a reduced risk of death due to heart disease. Also, taking vitamin K1 as a supplement seems to prevent or reduce the progression of coronary calcification, a risk factor for heart disease.
  • Cystic fibrosis. People with cystic fibrosis may have low levels of vitamin K. Taking a combination of vitamins A, D, E and K seems to improve vitamin K levels in people with cystic fibrosis who have problems with fat digestion. Early research also shows that taking vitamin K orally may enhance osteocalcin production. Osteocalcin plays a role in bone growth and metabolism. But there is no reliable evidence to suggest that vitamin K improves overall health in people with cystic fibrosis.
  • Diabetes. Research has shown that taking a vitamin K supplemented multivitamin does not reduce the risk of developing diabetes compared to taking regular multivitamin.
  • High cholesterol. There are first indications that vitamin K2 can lower cholesterol in people on dialysis with high cholesterol levels.
  • Rheumatoid arthritis. Early studies show that taking vitamin K2 along with arthritis treatment reduces bone markers better than by taking medication alone.
Is vitamin K safe?
The two forms of vitamin K (vitamin K1 phylloquinone and vitamin K2 menaquinone) are very safe for most people when taken orally or by appropriate infusion into the vein. Most people do not experience side effects when they take vitamin K at the recommended amount every day. However, some people may experience stomach upsets or diarrhea.

  • MedlinePlus – Trusted Health Information for you NIH, U.S. National Library of Medicine.
Related product: Complete D3, K2 & Co factors
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