The Nutrition Information Centre of the
University of Stellenbosch (NICUS)
Vitamins: Vitamin K
What is it?
There are three forms of vitamin K
Vitamin K1 comes from plant sources
Vitamin K2 is produced by intestinal bacteria
Vitamin K3 is produced synthetically
Functions - what does it do?
Blood Clotting. Vitamin K plays an essential role in normal blood clotting. It contributes to the synthesis of several blood-clotting factors.
Inactive blood-clotting factors
Action of vitamin K
Active blood-clotting factors
Without sufficient vitamin K, haemorrhaging (bleeding) occurs.
Bone Health. Vitamin K particpates in the synthesis of several bone proteins that are essential for bone formation. Research is in progress to determine the specific roles of these proteins in bone metabolism and the risk of osteporosis.
Requirements - How much do we need?
0 - 0.5 (0 - 6 months)
0.5 - 1 (7 - 12 months)
1 - 3
4 - 8
9 - 13
14 - 18
18 and younger
19 - 30
Ages 31 - 50
*Adequate Intakes (AI) are used as no RDA is established. The AI is a recommended daily intake level based on observed or experimentally determined approximations of nutrient intake by a group of healthy people who are assumed to be maintaining an adequate nutritional state.
Sources - Where is it found?
Liver, Green leafy vegetables (e.g. Kale, Turnip greens, Cabbage, Spinach), Broccoli, Peas, Green beans
Other vegetables, Fruits, Cereals, Dairy products, Eggs, Meat
Vitamin K is naturally produced by bacteria in the intestines.
Deficiency - When you have too little
Newborns lack the intestinal bacteria to produce vitamin K and need a supplement for the first week. A vitamin K injection is given at birth to provide the nutrient until enough bacteria are present in the infant's intestine to make the amounts needed.
In adults, deficiencies can occur in people using antibiotics for prolonged periods, possibly due to the destruction of the intestinal bacteria that produce vitamin K. People on anticoagulant drugs (blood thinners) and those suffering from severe chronic fat malabsorption may also become deficient.
Toxicity - When you have too much
Oral doses of vitamin K poses no risk of toxicity. Megadoses of vitamin K reduce the effectiveness of oral anticoagulant drugs (blood thinners) used by some people.