Vitamin K: Dietary Sources, Benefits and Deficiency
Vitamin K is a fat soluble nutrient that is needed for the blood to clot. Clotting is necessary following an injury to prevent uncontrolled bleeding. Blood clotting (or coagulation) is the end of a complex process which involves numerous proteins, enzymes and vitamin K.
The three existing forms of vitamin K include:
- Phylloquinone (K1). Found in plant foods, including oils.
- Menaquinone (K2). Produced by the body and found in animal foods (e.g., egg yolks or liver).
- Menadione (K3). Manufactured “synthetic” form.
RDA of Vitamin K
The daily recommended allowance (RDA) of vitamin K is 120mcg per day for adult men and 90mcg per day for adult women (over 19 years of age). There are no special allowances for pregnant or breastfeeding women. Although most adults living in the industrialized world get enough vitamin K through their diets to meet these recommendations, studies show that some children and older adults may not be getting as much as they should.
Vitamin K Deficiency
Vitamin K is different from other fat soluble vitamins, which can be easily stored in the liver and the fatty tissues of the body, in that the body stores very little of this particular vitamin. Therefore, deficiency may occur when certain diseases or medications prevent proper absorption of vitamin K. Examples include conditions such as bile-production failure, celiac disease, cystic fibrosis, Crohn’s disease, ongoing diarrhea or prolonged use of antibiotics and use of anticoagulant medications. Other possible causes of vitamin K deficiency include serious burns, ongoing hemodialysis, long-term use of total parenteral nutrition (TPN is provided intravenously) and ingesting too much mineral oil.
Elderly people are often at an increased risk of vitamin K deficiency because of taking too many medications, eating inadequate diets and possibly suffering from bacterial overgrowth which inhibits the production of vitamin K in the gut. Individuals with a deficiency of vitamin K may have problems with blood clotting and may also bruise easily.
Potential Health Benefits of Vitamin K
Vitamin K’s most important role in the body is in helping the blood to clot after an injury by activating proteins that cause blood to coagulate. This prevents a person from bleeding to death. In addition, vitamin K helps the body to synthesize proteins needed by the kidneys, bones and blood and plays an essential role in helping bones develop normally. Without enough vitamin K, bone density is low, which increases the risk of osteoporosis.
When the diet cannot provide enough vitamin K supplements may be used to reduce the risk of bleeding due to liver disease or malabsorption disorders. Women who experience heavy menstrual bleeding may also be prescribed vitamin K supplements. Other conditions that may be treated with increased intake of vitamin K include:
- Osteoporosis. Taking vitamin K supplements helps strengthen bones and reduce the risk of fractures, especially in post-menopausal women.
- Cystic fibrosis. Patients with cystic fibrosis often also have vitamin K deficiency due to prolonged use of antibiotics and may benefit from taking vitamin K supplements.
- Skin wounds. Water-soluble forms of vitamin K can be used to treat skin wounds.
- Heart disease. Studies indicate that vitamin K2 may help keep calcium out of artery linings and that vitamin K2 can be used in conjunction with vitamin D to prevent calcification of coronary arteries.
- Kidney stones. Supplementation with vitamin K may help prevent formation of kidney stones.
- Snake bites. Since some snake venoms destroy vitamin K to promote bleeding, an injection of vitamin K can arrest this process.
- Body odor. Vitamin K is sometimes also used to control body, fecal and urinary odor.
Too much vitamin K is not known to cause health problems or symptoms on its own. However, eating excessive amounts of foods rich in vitamin K should be avoided by people who use anticoagulants because vitamin K can prevent these medications from working properly.
Dietary Sources of Vitamin K
Bacteria in the body’s intestines can produce vitamin K, which is then stored in the liver. This accounts for about one half of a person’s needs. The remaining half must come from dietary sources. However, newborn infants need several weeks to begin producing these vitamin K-generating bacteria. Therefore, newborns typically receive a shot of vitamin K, which, though, is not without controversy.
The best dietary sources of vitamin K include liver and green leafy vegetables, especially the members of the cabbage family (cruciferous vegetables). Other good sources include eggs, fruits, vegetables (e.g. asparagus), cereals, milk and dairy products, meat and some unsaturated oils, especially the fish oil. Heating vitamin K does not destroy it but freezing does so.
Supplementation with Vitamin K
People with bleeding and bruising disorders may be prescribed vitamin K supplements. Supplements may also be beneficial to women who are at risk of osteoporosis. Although high doses of vitamin K do not seem to cause major health issues, certain populations may be at risk of adverse effects. For instance, pregnant women taking these supplements may cause jaundice in their children. In addition, vitamin K supplements cannot be recommended to people with certain medical conditions, including:
- Chronic diarrhea
- Cystic fibrosis or other diseases affecting the pancreas
- Gallbladder disease
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency
- Intestinal problems
- Liver disease
As it was mentioned earlier, certain medications, such as anticoagulants, antibiotics, laxatives and some cholesterol-reducing drugs, may interact poorly with increased intake of vitamin K. Therefore, you should not take vitamin K or any other supplement without first consulting a doctor.