There are several micronutrients which are required in small amounts to sustain life. These include a host of vitamins and minerals, each of which play important roles in various biochemical processes. One of these substances is vitamin K. A deficiency or total lack of vitamin K can have a number of effects on the human body, the most notable of which is a disturbance in the blood clotting process which is essential to prevent blood loss.
What is Vitamin K?
Vitamin K (VK) is a fat-soluble vitamin that is found in certain foods and synthesized by the bacteria in the human bowel. As a fat-soluble vitamin it is stored in the liver and fat tissue in the body. Vitamin K is not a single compound but a group of vitamins – K1 (phylloquinone), K2 (menaquinone) and K3 (menaphthone or menadione). Vitamin K1 and K2 are the natural forms of the vitamin while K3 is the synthetic form.
The human body has approximately one week of vitamin K stores so even a total lack of new vitamin K will not yield any clinical features in this time period at least. Almost all of the vitamin K absorbed into the bloodstream is through the end part of the small intestine known as the terminal ileum. As a fat-soluble vitamin, it does not enter the bloodstream directly but rather travels via the lacteals into the lymphatic system and is eventually drained into the bloodstream. Bile plays an integral role in vitamin K absorption.
Food and Other Sources of Vitamin K
Vitamin K is found in a number of food sources including :
- Leafy green vegetables like spinach, lettuce (dark green), cabbage, kale.
- Other vegetables like asparagus and broccoli.
- Meat like liver.
- Oils like olive, canola, soybean.
Vitamin K is sensitive to low temperatures as is seen with freezing foods but is resistant to high temperatures (heat) when cooking.
Vitamin K Supplements
Although a vitamin K deficiency is rare, supplementation may be necessary at times. Vitamin K supplements can be administered in table or capsule form (oral) or injections (parenteral). However, vitamin K is mainly derived from the gut where it produced by the colonic bacteria. Therefore vitamin K supplementation is often not necessary unless there is an existing disease associated with deficiency. Infants derive vitamin K from the mother across the placenta before birth and it is also sourced from the breast milk after birth.
Dose of Vitamin K
The dose of vitamin K varies by the person’s age and needs. Ideally a change in diet to include foods rich in vitamin K should first be considered if the deficiency is not severe. Supplements may be necessary once bleeding disorders are evident. Oral supplements are preferred over parenteral (injection) administration as the latter may cause localized hematomas.
Dietary recommendations by the Food and Nutrition Board at the Institute of Medicine is as follows :
- 0 to 6 months : 2.0 micrograms per day (mcg/day)
- 7 to 12 months : 2.5 mcg/day
- 1 to 3 years : 30 mcg/day
- 4 to 8 years : 55 mcg/day
- 9 to13 years : 60 mcg/day
Adolescents and Adults
- Males and females age 14 to 18 : 75 mcg/day
- Males and females age 19 and older : 90 mcg/day
Effects of Vitamin K
Simply, vitamin K plays a role in the chemical reaction that allows certain proteins to bind to membrane surfaces. This effect known as carboxylation then mediates the relevant part of the biochemical process. Therefore vitamin K acts as a co-factor to activate certain proteins in the body. Most of these proteins are involved the clotting process (coagulation and anticoagulation) but also activates certain proteins in the bone and those manufactured by the cells.
Vitamin K is utilized for the synthesis of clotting factors II, VII, IX and X. Without these clotting factors working efficiently, the coagulation cascade is affected and the formation of a blood clot is delayed. A person may find that even small cuts will bleed profusely. Vitamin K appears to help with maintaining bone strength especially in the elderly. A deficiency may therefore lead to fragile bones (osteoporosis) which breaks easily or results in multiple fractures.
Deficiency of Vitamin K
Since the body absorbs most of its vitamin K in the terminal ileum, diseases that affect this portion of the small intestine and particularly its absorptive functions may lead to a vitamin K deficiency. A small amount of vitamin K is derived directly from the food but most is produced by the colonic bacteria. If the bacterial population and therefore its actions is compromised, there will be insufficient vitamin K availability.
For adults, the following conditions may affect vitamin K availability and absorption :
- Chronic alcoholism
- Long parenteral nutrition – feeding a person intravenously (IV)
- Chronic illness
- Inflammatory bowel disease
- Celiac and tropical sprue
- Chronic pancreatitis
- Bile stasis and biliary disease
- Liver disease
- Drugs like antibiotics (destroy intestinal bacteria), bile acids (prevent VK absorption), warfarin (affects VK supply in the cell) and other drugs where the exact mechanism by which it causes vitamin K deficiency is unknown (barbituates, anticonvulsants).
For infants, the following conditions may affect vitamin K availability and absorption :
- Sterile gut (newborns without the natural intestinal bacteria)
- Lack of vitamin K in the breast milk
- Low supply from mother to fetus across the placenta
- Premature liver
Signs and Symptoms of Vitamin K Deficiency
Vitamin K affects the blood clotting process. This is an essential part of hemostasis – the mechanism which stops or prevents blood loss. In a vitamin K deficiency, the following signs and symptoms may be noticed :
- Easy and/or profuse bleeding
- Easy bruising (hematoma, ecchymosis)
- Petechiae – small red to purple spots under the skin
- Nosebleeds (epistaxis)
- Bleeding gums
- Bleeding from the gut – vomiting up blood (hematemesis), dark blood in stool (melena), fresh blood in stool (hematochezia)
- Heavy menses (menorrhagia)
- Blood in the urine (hematuria)
Vitamin K deficiency in fetal development may lead to birth defects evident as deformities of the face, nose and nose. Fragile bones may be associated with vitamin K deficiency although this is not a major factor as is the case with calcium and phosphorus deficiency. In these instances, there may be a history of repeated fractures.
Toxicity and Side Effects
Vitamin K toxicity is rare and only seen with the synthetic form (vitamin K3) especially if supplementation is by parenteral administration (injection). High doses and excessive administration of vitamin K may cause the following :
- Nausea and vomiting
- Blood clotting
- Hemolytic anemia (newborns)
Side effects of using vitamin K supplements are also rare but may include :
- Diminished appetite
- Swelling of the legs or entire body (edema)
- Difficulty breathing
- Muscle stiffness