Vitamin K

Vitamin K is not a single chemical substance, but rather a family of chemically related compounds, which goes by the generic title of "vitamin K." Over the last 20 years, has no vitamin family undergone a major change in the form of our scientific understanding of its chemistry and function. In the past, members of the vitamin K family have traditionally been referred to as vitamin K1, vitamin K2 and vitamin K3. This terminology is largely being replaced by another set of terms to describe what is now determined to be a more complicated set of vitamin K compounds.

All types of vitamin K fall in a large chemical group of substances called naphthoquinones. Within this category naphthoquinone, there are two basic types of vitamin K. The first type, called phylloquinone, is made from plants. The second basic type, called menaquinones, are made of bacteria. (The only exception to this rule involves a special group of bacteria called cyanobacteria, which makes phylloquinone instead of menaquinones.) Contrary to some previous scientific assumptions, we get most of our dietary vitamin K in the form of phylloquinone from plant foods. Actually coming up to 90% of our dietary vitamin K in this form, and within these 90%, more than half comes from vegetables, especially green leafy vegetables. Many different types of bacteria in our guts can make vitamin K in the form of menaquinones. While this synthesis of vitamin K in our digestive system can contribute to our vitamin K requirements, this contribution is less than previously thought.

What can high-vitamin K foods do for you? :

Let the blood to clot normally

Help protect your bones from fracture

Help prevent postmenopausal bone loss

Help prevent the calcification of blood vessels

Give maximum protection against liver and prostate cancer

What events can indicate a need for more high-vitamin K foods?

Excessive bleeding, including heavy menstrual bleeding, gum bleeding, bleeding in the gastrointestinal tract, or nosebleeding

Easy bruising

Problems with the calcification of blood vessels or heart valves

Problems with fractures or bone weakening

Excellent sources of vitamin K include: spinach, Brussels sprouts, Swiss chard, green beans, asparagus, broccoli, kale and mustard greens. Very good sources include green peas and carrots.

What are the functions of vitamin K? :

Promotes healthy blood clotting :

With regard to health, research, vitamin K is best known for his role in healthy blood clots. Indeed, initially using the letter "K" in the name of this vitamin came from the German word coagulation.

Although blood clotting may not sound like a body process that is crucial to our daily health, it is really important. At one end of the spectrum when we get a skin wounds (even a simple cut) we need sufficient blood clotting ability to close the wound and prevent excessive bleeding. At the other end of the spectrum, we do not want too much blood clotting ability, because when we are wounded, we do not want our cardiovascular system to "throw a clot" and mistakenly block a otherwise well-functioning blood vessels. Vitamin K is one of the most important nutrients to keep our blood clotting ability at the right level.

We owe much of our knowledge about vitamin K and clotting of the early experiments with the prescription drug warfarin. Also known as Coumadin, warfarin is a widely used anticoagulant drug that works by inhibiting the body's synthesis of coagulation factors (including coagulation factors II, VII, IX and X).

Vitamin K is sitting right in the middle of this coagulation. If the clotting factors that could close a wound, they need a way to stay at the nearby tissue surfaces. What gives them this "sticky" is a chemical event called carboxylation. One of the amino acids in clotting factors, called glumatic acid, is the part of the clotting factors that are carboxylated. Two enzymes are needed to keep this process running smoothly. Warfarin acts as an anticoagulant and interrupt this process by blocking one of these enzymes (vitamin K epoxide reductase). When this enzyme is blocked, vitamin K can no longer be recycled and "recharged" to help the clotting factors reach their proper stickiness. For people with an excessive tendency to form blood clots, blood thinners such as warfarin may be lifesaving. These warfarin-related discoveries have led to our current understanding of vitamin K as an essential nutrient for healthy blood clots.

Protects bones from weakening or fracture :

The relationship between vitamin K to bone health has been fairly well studied, and in the big picture, the vitamin K proved to be a critical nutrient for bone health. Most convincing is the research showing protection against fractures, which occur when vitamin K is consumed in sufficient quantities. Individuals who are vitamin K deficiency has been clearly shown to have a higher risk of fracture. Moreover, for women who have passed menopause and have begun to experience adverse bone vitamin K has been clearly shown to help prevent future fractures. These bone-related benefits of vitamin C appears to depend on at least two basic mechanisms.

The first of these mechanisms involves a type of bone cells called osteoclasts. Osteoclasts are bone cells responsible for bone demineralization, they help to minerals from the bones and make them available for other bodily functions. While the activity of these cells is important for good health, we do not want too many osteoclasts (or too much activity by osteoclasts) as these imbalances would mean too much bone demineralization. Vitamin K makes it possible for our bodies to keep this process in check. One of the menaquinone forms of vitamin K (MK-4, also called menatetrenone) has repeatedly been shown to block the formation of too many osteoclasts, and perhaps also to start their programmed cell death (a process called apoptosis).

A second mechanism involves the role of vitamin K in a process called carboxylation. (This process is the same as discussed earlier in relation to the stickiness of coagulation proper blood clotting.) For our legs to be optimally healthy, one of the proteins found in bone-a protein called osteocalcin-be chemically altered through the process of carboxylation. (Osteocalcin is not just a typical bone proteins. It is a protein that is particularly linked to our bone mineral density-BMD and for this reason, it is often measured in our blood when doctors try to determine the health of our bones.) When too few of the osteocalcin protein in our bones are carboxylated, our bones and increased risk of fractures. This unwanted risk seems to be particularly important in connection with hip fracture. Scientists refer to this bone problem as one involving "undercarboxylated Osteocalcin," and they have found that vitamin K can greatly improve the situation. Since vitamin K is necessary for proper activity of carboxylase enzyme that allows carboxylation of osteocalcin protein in our bones, vitamin C can restore these bone proteins to their proper place in our bone structure and strength of the composition of the bone. It is menaquinone MK-4 form of vitamin K, which has been best studied in this respect.

Prevents calcification of blood vessels or heart valves :

A common problem in many forms of cardiovascular disease is unwanted calcification, the build up of calcium inside a tissue that is normally soft. This accumulation of calcium sheep tissue to harden and stop functioning properly. When calcium builds up inside arteries, it is typically called arteriosclerosis. A direct way to inhibit the development of calcium along the arteries is to maintain ample supplies of a special protein called MGP in the body. MGP, or matrix Gla protein that directly blocks the formation of calcium crystals inside the blood vessels. For MGP to function in this way, it must first be present in its carboxylated form, vitamin K is necessary for this carboxylation process. In other words, heart-protective benefits of MGP in preventing calcification depend on vitamin K. In animal studies, both basic forms of vitamin K i.e., phylloquinone and menaquinones-found to provide excellent calcification-prevention benefits. Researchers have found that people with vitamin K deficiency are at greater risk for atherosclerosis than people with healthy vitamin K intake.

Other roles for vitamin K :

Researchers continue to investigate a wide range of health-supportive roles for vitamin K. At the forefront of this research has roles in three major areas: (1) protection against oxidative damage (2) proper regulation of the inflammatory response, and (3) support of brain and nervous system structure. With regard to protection against oxidative damage, has Vitamin K does not seem to function directly as an antioxidant in the same manner as other antioxidant vitamins (like vitamin E and vitamin C) do. But both phylloquinone and menaquinone forms of vitamin K seems useful in protecting cells, especially nerve-cells from oxidative damage. In terms of inflammatory response, several markers of pro-inflammatory activity, including, for example, release of interleukin-6 (IL-6)-are significantly reduced by healthy vitamin K levels. Finally, with regard to the brain and nervous system structure, Vitamin K is known to be required for the synthesis of a very important family of the brain and nervous system fats called sphingolipids. These fats are important in the formation of the myelin sheath, which forms an outer packaging around the nerves, and both phylloquinone and menaquinone forms of vitamin K have been found effective in supporting the synthesis of these central nervous system components. All of the above roles of vitamin K have been studied primarily in laboratory experiments on animals or in laboratory experiments on human cell samples.

What are deficiency symptoms for vitamin K? :

People who lack vitamin K is primarily likely to have symptoms related to the problematic blood clots or bleeding. These symptoms can include heavy menstrual bleeding, gum bleeding, bleeding in the gastrointestinal tract, nose bleeding, easy bruising, blood in urine, prolonged clotting, hemorrhaging, and anemia. Another set of vitamin K-deficiency symptoms involving skeletal problems. These symptoms may include loss of bone (osteopenia), decrease in bone mineral density (osteoporosis) and fractures, including common age-related fractures as in the hips. Another set of vitamin K deficiency symptoms include the deposition of calcium in soft tissues. These calcifications-based problems include arteriosclerosis or calcium-related problems with heart function.

What are the current public health recommendations for vitamin K? :

In 2000 established the National Academy of Sciences following Adequate intake (AI) levels for vitamin K:

Males and females 0-6 months: 2 micrograms

Males and females, 7-12 months: 2.5 micrograms

Males and females 1-3 years: 30 micrograms

Males and females 4-8 years: 55 micrograms

Males and females 9-13 years: 60 micrograms

Men and women 14-18 years: 75 micrograms

Men 19 years and older: 120 micrograms

Females 19 years and older: 90 micrograms

Pregnant or lactating females 18 years and younger: 75 micrograms

Pregnant or lactating females 19 years and older: 90 micrograms