Vitamin K is essential for normal blood clotting and bone metabolism, while vitamin K-dependent proteins are also being studied for their potential role in keeping calcium out of arteries and other soft tissues.
By yourNEWS Media Newsroom
Vitamin K may be best known as the nutrient that helps stop bleeding, but its biological reach extends well beyond the clotting process.
The fat-soluble vitamin activates a family of proteins involved in coagulation, bone metabolism and calcium regulation. Researchers have also been studying whether adequate vitamin K — particularly forms known as vitamin K2 — could help support cardiovascular health by activating proteins involved in limiting abnormal calcium deposits in blood vessels.
The evidence is strongest for vitamin K’s indispensable role in blood clotting. Its importance to normal bone function is also well established, although research remains mixed over whether taking additional vitamin K supplements prevents fractures or osteoporosis in otherwise adequately nourished people.
The cardiovascular picture is less settled. Vitamin K activates Matrix Gla-Protein, or MGP, which is involved in regulating calcification, but the National Institutes of Health says it remains unclear whether supplemental vitamin K meaningfully reduces arterial calcification or coronary heart disease risk.
Taken together, the research paints a picture of a nutrient that performs several fundamental jobs while also attracting growing interest for health effects scientists are still working to define.
Vitamin K Is a Family of Compounds
Vitamin K is not one molecule.
The two major forms are vitamin K1, or phylloquinone, and vitamin K2, a group of compounds known as menaquinones.
K1 is the principal dietary form in the United States and is found primarily in green leafy vegetables and some vegetable oils.
K2 includes several forms designated MK-4 through MK-13 according to their chemical structure. Menaquinones are found in fermented foods and modest amounts in certain animal foods, and several forms are also produced by bacteria in the gastrointestinal tract.
How much of the vitamin K produced by intestinal bacteria is actually absorbed and contributes to human requirements remains uncertain.
Natto, a traditional Japanese food made from fermented soybeans, is exceptionally rich in MK-7, one form of vitamin K2. Cheese can contain varying amounts of menaquinones depending on how it is produced, while poultry, eggs and certain other animal foods supply smaller quantities.
The distinction between K1 and K2 is useful, but it can also be oversimplified.
Both belong to the same vitamin family and participate in the activation of vitamin K-dependent proteins. K1 should not be viewed as exclusively a “clotting vitamin,” nor K2 as exclusively a “bone and heart vitamin.”
Their distribution, metabolism and biological availability differ, however, which is why researchers continue investigating whether individual forms have different long-term effects.
The Discovery Began With Unexplained Bleeding
Modern understanding of vitamin K began nearly a century ago through experiments that initially had nothing to do with human nutrition.
Danish scientist Henrik Dam was studying cholesterol metabolism in chickens during the late 1920s and early 1930s when animals fed a severely restricted diet began developing spontaneous bleeding.
Adding purified cholesterol did not correct the problem.
Dam eventually concluded that the chickens lacked another fat-soluble substance required for normal coagulation.
He called it “Koagulationsvitamin,” using the German and Scandinavian spelling for coagulation. The name was eventually shortened to vitamin K.
Dam shared the 1943 Nobel Prize in Physiology or Medicine with American biochemist Edward Doisy, whose work helped identify the vitamin’s chemical nature.
What began as an investigation into bleeding later revealed a nutrient involved in biological processes throughout the body.
Vitamin K Activates the Machinery That Stops Bleeding
Vitamin K acts as a cofactor for an enzyme that chemically modifies — or carboxylates — certain proteins so they can function properly.
Several of the proteins involved are essential components of the blood coagulation system.
They include clotting factors II, VII, IX and X, along with anticoagulant proteins C and S.
Without enough vitamin K, the liver cannot produce fully functional versions of these proteins. Blood consequently loses some of its ability to form an effective clot after an injury.
Severe deficiency can result in bruising or bleeding from the nose, gums, gastrointestinal tract, urinary tract or other sites. Internal hemorrhage can become life-threatening.
Clinically significant deficiency is uncommon among healthy adults eating varied diets.
According to the NIH Office of Dietary Supplements, adult vitamin K deficiency is generally associated with conditions that interfere with absorption or metabolism rather than simply failing to eat enough vitamin K on a particular day.
People with disorders involving fat malabsorption can be at increased risk because vitamin K is fat-soluble.
Conditions that may interfere with absorption include cystic fibrosis, celiac disease, short bowel syndrome and certain other gastrointestinal disorders. People who have undergone bariatric surgery can also develop inadequate vitamin K status.
Prolonged antibiotic use may reduce vitamin K-producing intestinal bacteria, particularly when combined with poor dietary intake, although antibiotics do not ordinarily cause clinically significant deficiency in otherwise healthy adults.
Vitamin K Helps Activate Osteocalcin in Bone
The connection between vitamin K and the skeleton centers heavily on osteocalcin, one of the major proteins produced by bone-forming cells.
Osteocalcin requires vitamin K-dependent carboxylation to function normally.
That biochemical process allows osteocalcin to interact with calcium and the mineral component of bone, helping explain why vitamin K has attracted considerable interest in osteoporosis research.
Some observational research has associated higher vitamin K intake or better vitamin K status with greater bone mineral density or lower fracture risk.
Studies of K2 have drawn particular attention.
Earlier trials involving pharmacological doses of MK-4, many conducted among postmenopausal women in Japan, reported reductions in certain fractures. A later trial using MK-7 found improvements in some measures of bone strength among postmenopausal women.
Other randomized trials, however, have found that vitamin K supplementation lowers levels of undercarboxylated osteocalcin without producing significant improvements in bone mineral density.
That means the biological relationship is clearer than the supplement question.
Vitamin K is required for normal osteocalcin activation and bone metabolism. But evidence does not establish that everyone will strengthen bones or prevent fractures by taking extra K2 beyond an adequate diet.
The NIH therefore says it remains unclear whether supplementation with any form of vitamin K reduces the risk of osteoporosis.
Adequate calcium, vitamin D, resistance and weight-bearing exercise, sufficient protein and other nutritional and lifestyle factors remain important components of maintaining skeletal strength.
K2 and Arterial Calcification Remain an Active Area of Research
Another vitamin K-dependent protein has generated considerable interest in cardiovascular research.
Matrix Gla-Protein is present in vascular smooth muscle, cartilage and bone and appears to help regulate abnormal mineral deposition.
Like osteocalcin, MGP must be activated through a vitamin K-dependent process.
That has led researchers to investigate whether inadequate vitamin K could leave more MGP inactive, potentially making it easier for calcium to accumulate in arterial walls.
Vascular calcification is associated with arterial stiffness and cardiovascular disease.
Several observational studies have found associations between higher menaquinone, or K2, intake and lower levels of coronary or aortic calcification.
Some studies have also reported lower cardiovascular mortality among people consuming more dietary K2.
Those findings have generated claims that K2 “keeps calcium out of the arteries.”
The science is more cautious.
MGP appears to participate in controlling calcification, but observational associations cannot prove that higher K2 intake itself caused better cardiovascular outcomes. People who consume different diets may also differ in numerous other health behaviors.
Clinical trials have so far produced insufficient evidence to recommend vitamin K supplements specifically for preventing heart disease.
“At this time, the role of the different forms of vitamin K on arterial calcification and the risk of coronary heart disease is unclear,” the NIH concludes.
That does not make the biological mechanism unimportant. It means scientists have not yet established that manipulating vitamin K intake through supplements produces the cardiovascular outcomes suggested by laboratory and observational research.
Newborns Face a Very Different Vitamin K Problem
Vitamin K deficiency is rare in healthy adults but represents a particular danger for newborn babies.
Infants are born with very small vitamin K stores because relatively little crosses the placenta during pregnancy.
Their intestines also do not yet contain the established bacterial population found in older children and adults, and breast milk contains relatively little vitamin K.
That combination creates a risk of vitamin K deficiency bleeding, or VKDB.
A newborn with VKDB may bleed into the gastrointestinal tract, skin or other tissues. In severe cases, bleeding can occur inside the brain without obvious warning beforehand.
The Centers for Disease Control and Prevention says infants who do not receive vitamin K after birth can develop VKDB as late as 6 months of age and that about half of babies who develop the condition experience bleeding in the brain.
The American Academy of Pediatrics has recommended routine vitamin K prophylaxis at birth since 1961.
A single intramuscular vitamin K injection shortly after delivery dramatically reduces the risk of VKDB.
The CDC says infants who do not receive the injection are 81 times more likely to develop late vitamin K deficiency bleeding than babies who do receive it.
Maternal dietary supplementation does not provide enough vitamin K through breast milk to substitute reliably for newborn prophylaxis.
Leafy Greens Are Among the Richest Sources
For adults, obtaining vitamin K from food generally is not difficult.
Some of the richest sources of K1 are dark green vegetables.
Collard greens, turnip greens, spinach, kale, broccoli and similar vegetables can provide substantial amounts.
Soybean and canola oils also contribute K1, as do smaller amounts from foods such as blueberries, grapes and certain nuts.
Eating vegetables with some dietary fat can improve absorption because vitamin K is fat-soluble.
The food profile for K2 is quite different.
Natto is by far one of the richest known dietary sources of MK-7. Fermented cheeses provide varying amounts of other menaquinones, while chicken, eggs, pork and some dairy products can supply smaller quantities.
The vitamin K composition of fermented foods can vary substantially depending on the bacteria and production methods involved.
That variability is one reason nutritional databases contain far more complete information for K1 than for K2.
Cooking does not automatically eliminate vitamin K. Leafy vegetables remain excellent sources when steamed, boiled or sautéed.
Because cooked greens lose water and shrink dramatically, a serving of cooked greens can actually contain a large amount of vitamin K simply because more leaves fit into the same volume.
Adults Need Relatively Small Daily Amounts
Unlike many nutrients, vitamin K does not have a formal Recommended Dietary Allowance because researchers lacked enough evidence to establish an Estimated Average Requirement.
Instead, the National Academies established an Adequate Intake.
For adults 19 and older, the AI is:
- 120 micrograms per day for men.
- 90 micrograms per day for women, including during pregnancy and breastfeeding.
Those recommendations refer to total vitamin K rather than setting separate requirements for K1 and K2.
A diet regularly containing leafy green vegetables can easily provide those amounts.
The NIH lists a half-cup of boiled collard greens at about 530 micrograms of K1, a half-cup of boiled turnip greens at roughly 426 micrograms and a cup of raw spinach at about 145 micrograms.
Natto provides very high amounts of K2, particularly MK-7.
For most healthy adults, food can therefore supply ample vitamin K without supplementation.
Supplements Come in Several Forms
Vitamin K supplements can contain K1, MK-4, MK-7 or combinations of those forms.
MK-7 has become common in supplements marketed for bone and cardiovascular support because it remains in circulation longer than some other forms.
However, a supplement’s ability to increase blood concentrations or activate vitamin K-dependent proteins does not automatically mean it has been proven to prevent fractures, heart attacks or other clinical outcomes.
That distinction matters when evaluating health claims.
There is no established Tolerable Upper Intake Level for naturally occurring K1 or K2 because vitamin K has shown a low potential for toxicity.
But that does not mean supplementation is appropriate for everyone.
The most important caution involves anticoagulant medications.
Warfarin Users Should Keep Vitamin K Intake Consistent
Warfarin works by interfering with vitamin K activity.
As a result, large or sudden changes in vitamin K consumption can change the medication’s anticoagulant effect.
Someone taking warfarin should not suddenly eliminate leafy greens, nor should that person begin taking high-dose K1 or K2 supplements without discussing the change with the clinician managing the medication.
The key is consistency.
The NIH advises people taking warfarin or similar vitamin K-antagonist anticoagulants to maintain a consistent intake of vitamin K from both foods and supplements.
That advice applies even to otherwise healthy foods such as spinach and kale.
Newer anticoagulants work through different mechanisms and are not all affected by vitamin K in the same manner, but medication-specific guidance should come from a physician or pharmacist.
What the Evidence Supports — and What It Does Not
Vitamin K’s essential role in human health is not in question.
Without it, normal coagulation fails.
The vitamin also activates osteocalcin and other proteins involved in bone metabolism, supporting its recognized role in maintaining normal bone.
Its involvement with MGP provides a plausible biological link to regulation of vascular calcification.
Where the evidence becomes less certain is in turning those mechanisms into broad claims about supplementation.
Research does not yet establish that taking K2 supplements prevents cardiovascular disease in the general population.
Studies of bone health have produced promising findings, particularly in some groups of postmenopausal women, but randomized trials have not been uniformly positive.
And although intestinal bacteria manufacture menaquinones, scientists still do not know precisely how much of that vitamin K becomes available to the body.
For most healthy adults, the practical approach remains relatively simple: eat a varied diet that regularly includes vitamin K-rich vegetables and other whole foods.
Those who have malabsorption disorders, take medications that affect vitamin K or are considering concentrated K2 supplements for a specific health condition may need individualized guidance.
Vitamin K may no longer be known solely as the clotting vitamin discovered through bleeding chickens nearly a century ago.
Modern research has revealed a much broader biological role — activating proteins that help control blood clotting, participate in bone mineralization and regulate where calcium is deposited in the body.
The science surrounding some of its proposed benefits continues to evolve, but its fundamental importance does not: vitamin K is an essential nutrient whose effects reach from the bloodstream to the skeleton and potentially into the health of the cardiovascular system.
Source: Natural News
Watch and learn about the health benefits of Vitamin K.
This video is from Holistic Herbalist channel on Brighteon.com.
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