The Essential Function of Vitamin K

The Essential Function of Vitamin K: What You Need to Know About the Vitamin You Probably Don't Know You Need

When most of us think about vitamins, we think of vitamin C, or maybe A, B, D, or E. The vitamin everybody needs but many of us don't know about is vitamin K. Here's what you need to know about vitamin K in maintaining good health.

The sole vitamin K function in your body is to make the proteins that control calcium. The physiological function of vitamin K is to convert the amino acid glutamate into gamma-carboxyglutamic acid (GCA). There are only about a dozen proteins known to contain GCA, but the tasks they perform are vital to good health. Here is the function of vitamin K in terms of this modified amino acid:

Vitamin K makes the proteins that allow blood to clot.

The K in the name of this vitamin is short for the German word "Koagulation." Vitamin K makes it possible for GCA to "siphon" calcium out of the bloodstream. The combination of calcium and specialized proteins forms a floating net in the bloodstream. This floating net forms a framework for the clot that in turn keeps blood in its proper channels. Clots prevent excessive bleeding.

If your diet or supplement program doesn't support the function of vitamin K, you are at risk of excessive bleeding. Vitamin-K rich foods and supplements are useful in keeping cuts, scratches, and other wounds from becoming "gushers" that cause an serious loss in blood volume.

Another function of vitamin K is to get calcium into bones.

The creation of mineral-dense, strong bones results from an interplay between the function of vitamin K and vitamin D. The bone making cells called osteoblasts move calcium in response to a hormone called osteocalcin. This hormone is regulated by vitamin D.

Vitamin D can't activate osteocalcin, however, except in the presence of three byproducts of glutamate. Making these three proteins from glutamate requires vitamin K. You can't get calcium into your bones if you aren't getting calcium in your diet, but too little calcium usually isn't the real reason bones are weak. Your bones can't use calcium without the function of vitamin K and D.

Another function of vitamin K is keeping calcium out of your arteries.

Everyone's heard of "hardening of the arteries," more technically termed atherosclerosis or arteriosclerosis. Hardened arteries result from calcium replacing cholesterol in the lining of a blood vessel.

This process of calcification occurs when a very small, microscopic amount of cholesterol becomes lodged in the arterial wall. A specialized group of white blood cells called macrophages feed on bacteria when there's an infection and on cholesterol when there's not. They patrol the bloodstream looking for cholesterol to surround, digest, and remove from the arteries.

In atherosclerosis, however, a macrophage gets imbedded in the arterial wall. A series of changes caused by antioxidant deficiency keep it from getting out.. It dies trying to remove, and other macrophages are signaled to act as "undertakers" and remove both the dead macrophage and the oxidized cholesterol.

Sometimes they die, too. Eventually there can be a visible mass (usually the size of the dot on top of an i, but sometimes a lot larger) consisting of a tiny bit of cholesterol and a whole lot of dead macrophages.

Over a period of weeks, months, or years, depending on antioxidant status, the detritus of macrophages and cholesterol usually is slowly replaced by artery-hardening calcium. Vitamin K, however, keeps that from happening. Just as vitamin K makes sure calcium moves into bones, another function of vitamin K is to keep calcium out of arterial clogs.

When arteries aren't clogged up with calcified cholesterol, they move more blood at a lower pressure. When arteries are open, any clots that do form are far less likely to lead to heart attack or stroke. There's a growing body of science that suggests that a function of vitamin K is to maintain the linings of blood vessels in a flexible condition - so even if there is a clot to lodge to cause a heart attack or stroke, the effects of the event will not be catastrophic.

Clinically significant vitamin K deficiency isn't very common. The definitive sign of vitamin K shortages in diet or supplementation is problems with blood clotting. It's very easy for your doctor to diagnose a vitamin K-related deficiency in blood clotting factors with a simple blood test.

Deficient function of vitamin K may also manifest itself as nosebleed, bleeding gums, heavy menstruation, blood in the stool, blood in the urine, black or tarry stools, tinted urine, or easy bruising. In the very rare case of vitamin K deficiency in infants, there can be life-threatening bleeding in within the skull.

This condition doesn't occur without other obvious symptoms, however, and it's most likely in babies who are breastfed by mothers who take anti-seizure medications.

So how do you get your vitamin K?

There was a time when nutritionists believed that most of the body's vitamin K was made by bacteria living in the colon. On the basis of this theory, pediatricians gave babies vitamin K shots. The theory was that injections were necessary because the newborn's digestive tract hadn't had enough time to make vitamin K.

There were headline reports in the 1980's and 1990's that giving newborn babies vitamin K shots could cause leukemia later in childhood. The scare mongering simply wasn't based on facts.. A follow-up study of 1.3 million babies in the United Kingdom found that this dreaded childhood disease was no more likely among children who received vitamin K in the delivery room than among children who didn't.

Nutritionists did, however, eventually learn that the best way to get your vitamin K is day by day. To maintain normal function of vitamin K, women need up to 90 micrograms a day and men need up to 120 micrograms a day.

Life StageAge Males(micrograms/day)Females(micrograms/day)
Infants0-6 months22
Infants7-12 months2-32-3
Children1-3 years3030
Children4-8 years5555
Children9-13 years6060
Adolescents14-18 years7575
Adults19 years and older12090
Pregnancy18 years and younger-75
Pregnancy19 years and older-90
Breastfeeding18 years and younger-75
Breastfeeding19 years and older-90
Adequate Intake (AI) for Vitamin K
(Source for Function of Vitamin K information : Institute of Medicine, Food and Nutrition Board, January 2001.)

A terrific source of vitamin K is leafy green vegetables.

A so-so source of vitamin K is cooking oil of plant origin. Here's a brief list of foods with vitamin K.

FoodServingVitamin K (micrograms)
Broccoli, cooked1 cup (chopped)420
Canola oil1 Tablespoon19.7
Kale, raw1 cup (chopped)547
Leaf lettuce, raw1 cup (shredded)118
Mayonnaise1 Tablespoon11.9
Olive oil1 Tablespoon6.6
Parsley, raw1 cup (chopped)324
Soybean oil1 Tablespoon26.1
Spinach, raw1 cup (chopped)120
Swiss chard, raw1 cup (chopped)299
Watercress, raw1 cup (chopped)85

Experts agree that green leafy vegetables are tops for vitamin K. A top-ten line-up of sources of vitamin K would rank vegetables in this order: Raw amaranth leaves, raw parsley, raw Swiss chard, cooked kale, raw watercress, cooked spinach, raw spinach, cooked turnip greens, raw collards, and cooked collards are the most highly concentrated foods with Vitamin K, in that order. Next on the list would be a few exotic foods, lamb's quarters (the plant, not the meat), chrysanthemum leaves (served with Japanese food) and chicory among them. Almost any vegetable contains at least a little vitamin K.

To make sure your body absorbs vitamin K from food, use at least a little oil in cooking or dressing your leafy greens. Vitamin K dissolves in fat, not water, so you need fat to carry vitamin K to your colon. Olive oil works best.

What's your RDA of vitamin K? Generally speaking, you need to eat enough foods with vitamin K to get about a milligram (1,000 micrograms) a week.

That's the vitamin K 2 cups of chopped raw kale. Or the vitamin K in 10 cups of lettuce. It's also theoretically to get all your vitamin K for a week by eating a small jar of mayonnaise, but it isn't necessary to slather on the mayo or to turn green with chlorophyll just to ensure you get your RDA of vitamin K. Just take supplemental vitamin K.

In North America, Australia, and New Zealand, vitamin K is available without prescription. It's a safe supplement. Although there is a remote chance of an allergic reaction, vitamin K1, the kind of vitamin K found in food (phylloquinone), and vitamin K2, a form of the vitamin found in supplements made in Japan (menaquinone), are essentially impossible to overdose.

Where care is required is in taking supplements made with vitamin K3. This is the chemical also known as menadione. This form of the vitamin, however, is only available by doctor's prescription in North America or Europe.

It's better if your K is part of a complete nutritional supplement that's easy to remember. Getting your vitamin K isn't the only reason to eat your greens, so it's a good plan to include some kind of dark, green leafy vegetable in your diet several times week. For your "vitamin insurance," take supplemental K.



More than the function of vitamin K at the home page.

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