Vitamin K is required for proper blood clotting and bone formation, as it helps in transporting the calcium in the body. Doctors usually prescribe vitamin K to treat an overdose of the anticoagulant drug called warfarin. It is also used as a preventive measure against excessive bleeding in patients taking warfarin who need to undergo a surgery. The letter 'K' stands for 'koagulering', the Danish word for 'clotting', since it was a Danish scientist, Dr. Henrik Dam, who discovered this vitamin.
Different Types of Vitamin K
The intestines can produce this vitamin, a function that can be enhanced by including cultured milk, such as yogurt in the diet.
There are two types of vitamin K that occur naturally: K1, also known as phylloquinone, occurs in plants K2, also known as menaquinone, is synthesised by the bacteria in intestines. Another type called vitamin K3, also known as menadione, is a synthetic type of this vitamin, which is produced by pharmaceutical companies.
This vitamin is categorised as a fat-soluble vitamin, which means that it is absorbed by the body and is deposited in the fat tissues, thus, reducing the requirement of ingesting it in large quantities. This can lead to two possibilities: Firstly, taking too much of this vitamin may result in toxicity, and secondly, the symptoms observed due to the deficiency of this vitamin may take years to manifest itself.
Recommended Dietary Allowance
The recommended dietary allowance (RDA) for vitamin K is 120 micrograms (mcg) per day for men and 90 mcg for women between the age of 19 and above and 75 mcg for both boys and girls between the ages of 14 to 18. For children:
- Between 0 to 6 months: 2 mcg
- Between 7 to 12 months: 2.5 mcg
- Between 1 to 3 years: 30 mcg
- Between 4 to 8 years: 55 mcg
- Between 9 to 13 years: 60 mcg
In pregnant or breastfeeding women between the age of 19 to 50, it is 90 mcg, and it is 75 mcg in those whose age is less than 19. While some of the vitamin K is produced by the microbes in the intestines, most of it is obtained from the food we eat. While, care must be taken to be aware that this recommended dosage is just the minimum that is required each day in order to avoid deficiency of this nutrient however, it should not be consumed in excess of the recommended amounts, except under stringent medical supervision. This is because it has the potential of raising the toxicity levels, as it is a fat-soluble vitamin.
Vitamin K Deficiency Symptoms
In adults, a deficiency of this vitamin can result in internal haemorrhage
, whereas in newborn babies, it causes hemorrhagic disease, hematuria
, and postoperative bleeding. It can also result in intracranial haemorrhages and muscle hematomas.
Vitamin K Overdose Symptoms
In otherwise healthy people, toxicity rarely occurs due to the dietary ingestion of vitamin K however, it can take place if vitamin K3, the synthetic form of the vitamin, is taken. Excessive intake and toxicity of this vitamin can result in sweating and flushing. Anaemia
may also occur. People who are on medication for the prevention of blood clotting need to consult their doctors before taking a supplement of vitamin K.
Effects of Vitamin K in the Diet
Why is vitamin K important for people on warfarin?
- As has been mentioned above, vitamin K is required by the body for controlling blood clotting. It is essential for the creation of the liver protein, prothrombin, which precedes the formation of thrombin (a vitally important factor in blood clotting).
- Also, since this vitamin is associated with the formation and repair of bones, it is thought to alleviate the severity or incidence of osteoporosis as well as the slow loss of bones.
- It also helps in converting glucose into glycogen in the intestines, which is then stored in the liver.
There are several medical conditions which require the prevention of excessive clotting in the body. Blood clots in the arteries, veins, and heart can cause phlebitis, strokes, and heart attacks. Warfarin, a blood thinner, is one such drug that is used for preventing clot formation
in such patients. This drug does this by interfering with prothrombin produced in the liver. Every patient prescribed warfarin has to undergo a blood test known as prothrombin time
, P.T., or pro time in order to determine the correct dosage. An excessive dosage results in bleeding, while a dosage that is too low does not prevent clotting.
So, the reason why vitamin K in the diet is important for people on warfarin is because if too much of it is consumed, it can interfere with the effects of warfarin
, resulting in the formation of blood clots.
However, people on anticoagulant medications need not avoid foods that contain vitamin K altogether. Rather, they need to keep the consumption more or less consistent, instead of ingesting a lot in a single day and very little the next day. This will help the anti-clotting drug to control the formation of blood clots. Maintaining a food diary to monitor the potential interaction between the medication and diet can prove to be beneficial. In case the P.T., gets too low, the doctor will be able to determine if the consumption of foods containing vitamin K was high, by referring to the food diary.
Foods Rich in Vitamin K
Green leafy vegetables are the richest source of vitamin K. Some of these are celery, spinach, Swiss chard, kale, collard greens, watercress, Brussels sprouts, scallion, endive, broccoli, lettuce, turnip greens, cabbage, mustard greens, spring onions, and asparagus. It is also found in cheese, liver, bacon, coffee, and green tea.