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Vitamin K

Posted on 27. Dec, 2010 by .

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Vitamin K is a fat-soluble vitamin, so it is stored in the body’s fat tissue and liver. It is best known for its role in helping blood clot (coagulate) properly (the “K” comes from its German name, Koagulationsvitamin). Vitamin K is known as the clotting vitamin, because without it blood would not clot.Vitamin K also plays an important role in bone health.

It is rare to have a vitamin K deficiency, because in addition to being found in leafy green foods, the bacteria that are found in the intestines can make vitamin K. Sometimes taking antibiotics can kill the bacteria and lead to a mild deficiency. Vitamin K deficiency can lead to excessive bleeding (hemorrhage), which may begin as oozing from the gums or nose. Other circumstances that may lead to vitamin K deficiency include:

* Health problems that can prevent the absorption of vitamin K (such as gallbladder or biliary disease, which may alter the absorption of fat), cystic fibrosis, celiac disease, and Crohn’s disease
* Liver disease
* Use of blood-thinning medications (such as warfarin)
* Continuing hemodialysis
* Serious burns

Other conditions that benefit from vitamin K include:

Excessive Bleeding

Vitamin K is used to reduce the risk of bleeding in liver disease, malabsorption syndromes, or in association with long-term use of antibiotics.

In the U.S., Canada, Great Britain, and many other countries, all newborns receive vitamin K injections to prevent the possibility of hemorrhage (particularly in the brain) just after delivery. Babies are born without any bacteria in their intestines and do not get enough vitamin K from breast milk to tide them over until their bodies are able to make it. (However, if a mother eats lots of green vegetables on a daily basis, she can improve the amount of vitamin K in breast milk.) Even though vitamin K deficiency in newborns is very rare, it is dangerous enough to warrant these measures. Newborns at greatest risk for vitamin K deficiency are those who are born prematurely or whose mother had to take seizure medications during pregnancy. Mothers on seizure medications are often given oral vitamin K for 2 weeks prior to delivery.

Osteoporosis

Vitamin K is needed for proper use of calcium in bones. Higher vitamin K levels correspond to greater bone density, while low levels of vitamin K have been found in those with osteoporosis. There is increasing evidence that vitamin K improves bone health and reduces risk of bone fractures, particularly in postmenopausal women who are at risk for osteoporosis. In addition, studies of other groups (such as male and female athletes) have also shown bone enhancing benefits from vitamin K supplements.

Dietary Sources:

Foods that contain a significant amount of vitamin K include beef liver, green tea,soybeans, turnip greens, broccoli, kale, spinach, cauliflower,cabbage, asparagus, and dark green lettuce. Chlorophyll is the substance in plants that gives them their green color and provides vitamin K.Vitamin K is also made by the bacteria that line the gastrointestinal tract

Freezing foods may destroy vitamin K, but heating does not affect it.
Available Forms:

There are 3 forms of vitamin K:

* Vitamin K1 (phylloquinone, the natural version of K1 and phytonadione, the synthetic type of K1)
* Vitamin K2 (menaquinone)
* Vitamin K3 (menaphthone or menadione)

K1 and K3 are both available as part of multivitamin complexes or alone, in 5 mg tablets. These fat-soluble forms are an excellent source of vitamin K.

Water-soluble chlorophyll is the most common form of vitamin K found over the counter. It is available in tablet, capsule, and liquid forms.
How to Take It:

As with all supplements, check with a health care provider before taking vitamin K or giving it to a child.

People with vitamin K deficiencies related to malabsorption (such as gallbladder or biliary disease, cystic fibrosis, celiac disease, and Crohn’s disease) will benefit most from a multivitamin containing vitamin K, rather than an individual vitamin K supplement. In certain circumstances, your doctor may administer vitamin K by injection.

Daily intake for dietary vitamin K (according to the U.S. RDA) are listed below:

Pediatric

* Infants birth – 6 months: 2 mcg
* Infants 7 – 12 months: 2.5 mcg
* Children 1 – 3 years: 30 mcg
* Children 4 – 8 years: 55 mcg
* Children 9 – 13 years: 60 mcg
* Adolescents 14 – 18 years: 75 mcg

A single injection of vitamin K is also given at birth.

Adult

* Males 19 years and older: 120 mcg
* Females 19 years and older: 90 mcg
* Pregnant and breastfeeding females 14 – 18 years: 75 mcg
* Pregnant and breastfeeding females 19 years and older: 90 mcg

Precautions:

Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider.

At recommended doses, vitamin K has few side effects.

Vitamin K crosses the placenta and is also excreted in breast milk. Therefore, pregnant women and women who are breastfeeding should talk to their doctor before taking vitamin K supplements.

People with an rare metabolic condition called Glucose-6-phosphate dehydrogenase (G6PD) deficiency should avoid vitamin K.
Possible Interactions:

If you are currently being treated with any of the following medications, you should not take vitamin K without first talking to your health care provider.

Antibiotics — Antibiotics, particularly a class known as cephalosporins, reduce the absorption of vitamin K in the body. Long-term use (more than 10 days) of antibiotics may result in vitamin K deficiency because these drugs kill not only harmful bacteria but also beneficial, vitamin K-activating bacteria. This is not likely to occur in people who already have low levels of vitamin K or are at risk for deficiency (such as those who are malnourished, elderly, or taking warfarin). Cephalosporins include:

* Cefamandole (Mandol)
* Cefoperazone (Cefobid)
* Cefmetazole (Zefazone)
* Cefotetan (Cefotan)

Phenytoin (Dilantin) — Phenytoin interferes with the body’s ability to use vitamin K. Taking anticonvulsants (such as phenytoin) during pregnancy or while breastfeeding may deplete vitamin K in newborns.

Warfarin (Coumadin) — Vitamin K reduces the effects of the blood thinning medication warfarin, rendering the medication ineffective. You should not take vitamin K, or eat foods containing high amounts of vitamin K, while you are taking warfarin.

Orlistat (Xenical, Alli) and Olestra — Orlistat, a medication used for weight loss, and olestra, a substance added to certain food products, prevent the absorption of fat and can reduce the body’s absorption of fat-soluble vitamins. The Food and Drug Administration now requires that vitamin K and other fat-soluble vitamins (A, D, and E) be added to food products containing olestra. In addition, physicians who prescribe orlistat add a multivitamin with fat soluble vitamins to the regimen.

The fact that vitamin K is now added to olestra-containing foods is important to know if you should not be taking vitamin K (if you are on the blood thinner warfarin, for example).

Bile acid sequestrants — These medications, used to reduce cholesterol, reduce the overall absorption of dietary fats and may also reduce absorption of fat-soluble vitamins. If you take one of these drugs, your doctor may recommend a vitamin K supplement:

* Cholestyramine (Questran)
* Colestipol (Colestid)
* Colsevelam (Welchol)

How Vitamin K Deficiencies Occur

Human intake of vitamin K comes from two main sources – our diets and synthesis from intestinal bacteria. Vitamin K deficiencies can be caused by a variety of factors. These include:

* Not consuming enough vitamin K from one’s diet can contribute to a deficiency. Dietary vitamin K is highest in leafy green vegetables such as lettuce, kale, broccoli and collard greens. These are foods that many people don’t eat frequently.

* A diet with high intakes of salicylates can block vitamin K. Salicylates are found in foods such as nuts, fruits, spices and mints. Aspirin is a salicylate. Blocking vitamin K is why aspirin can “thin” the blood – it basically keeps blood from coagulating. This is why too much aspirin may be a factor in bleding related health issues such as epistaxis (nose bleeds), as well as brain and intestinal bleeding.
* Antibiotics can cause bleeding problems from vitamin K deficiencies. Antibiotics destroy not only harmful digestive tract bacteria, but also the beneficial intestinal bacteria that is needed to create vitamin K. In order to replace the beneficial intestinal bacteria after a course of antibiotics it is often recommended to eat yogurt with active cultures or have to take probiotic supplements containing acidophilus. In the U.S. You can usually get the supplements at most drug stores or health food stores. The refrigerated kind is often best because the cultures last the longest when they have been kept cold.

Replacing beneficial bacteria after antibiotics is standard conventional medical advice in many European countries, but does not seem to be common medical advice in the United States.

*Candida (systemic yeast) infections have been linked to vitamin K deficiencies. An overgrowth of candida albicans or other kinds of yeast can crowd out the helpful bacteria in the digestive tract that make vitamin K. People who eat a lot of sugary foods, an unusually high proportion of alkaline foods and/or take antibiotics tend to be at high risk for Candida infections.

*Malabsorption syndromes that prevent the proper absorption of nutrients can cause vitamin K deficiencies. Celiac disease, an intolerance to gluten, can cause deficiencies of a wide variety of nutrients, especially vitamin K. Crohn’s disease can also cause vitamin K and other deficiencies.

*Anticoagulants like Warfarin block the action of vitamin K. In turn, vitamin K blocks the action of anticoagulants. This is why people taking these types of medications have to limit how much vitamin K they get in their diet.

*High amounts of vitamin A and/or vitamin E can also block vitamin K. I get nosebleeds whenever I take a multivitamin or eat one of the popular nutrition bars, even if I choose one with vitamin K. I think it may be at least in part because the multivitamins and nutrition bars always contain high amounts of vitamin A and E–probably too much for someone like me who bleeds easily.

*The bacteria that synthesize vitamin K thrive in an acidic digestive environment. Antacids, if taken in sufficient quantity, may cause a vitamin K deficiency, as well as irritable bowel syndrome and various nutritional deficiencies, because they neutralize the hydrochloric acid in a person’s stomach. Hydrochloric acid is needed to digest food and create the acidic environment in which the beneficial bacteria thrive.

(For more information on this topic, see my section on Acidic Foods – Alkaline Foods.

*One study found vitamin K deficiencies to be common in male alcoholics. (Perhaps not coincidentally, children born with fetal alcohol syndrome share many overlapping borth defects linked to vitamin K deficiencies.)

*In rats, butylated hydroxytoluene (BHT), a food preservative, was shown in tests to induce vitamin K deficiencies. BHT is a common preservative. Many commercial cereal boxes are sprayed with BHT to extend the shelf life of the product.

Regular aspirin use may raise the risk of bleeding strokes in healthy people. A study from Oxford University found that large numbers of older people suffered from bleeding in the brain when they took aspirin or other antithrombotic drugs. Another study from the Wolfson Institute of Preventive Medicine in London found that aspirin use caused a risk of serious bleeding in men with high blood pressure.

Alternative Names:

Menadione; Menaphthone; Menaquinone; Phylloquinone

thank you and references

http://www.umm.edu
http://www.nlm.nih.gov/medlineplus/ency/article/002407.htm
http://www.ctds.info/vitamink.html

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