Are You Getting Enough Vitamin K?
For years, vitamin K has been the neglected stepchild in the world of nutrition, while vitamins C, D, E, beta-carotene, and others grabbed all the attention. Groundbreaking research, however, is propelling vitamin K into the limelight.
This is long overdue because vitamin K has a plethora of health benefits. In addition to protecting against osteoporosis, arterial calcification, heart attacks, and cardiovascular death, it also appears to reduce risk of diabetes and some types of cancer. Because most of us don’t get enough vitamin K in our diets, everyone should sit up and take notice. However, if you are one of the millions who are taking Coumadin (warfarin), your life may depend on it.
The “Koagulation” Vitamin
Vitamin K is best known for its role in blood coagulation. Henrik Dam, a Danish biochemist who won a Nobel Prize for this work, discovered a food substance that, when eliminated from the diet, caused uncontrolled bleeding. When he published his findings in a German medical journal in the early 1930s, this substance was identified as “Koagulationsvitamin”—hence the name, vitamin K.
Vitamin K’s specific function wasn’t understood until the 1970s. We now know that it is required for the activation of a family of proteins known as Gla proteins, which bind to calcium. Fourteen Gla proteins have been discovered thus far. One of the best known—to people on Coumadin anyway—is prothrombin. It’s is an essential, calcium-dependent component of blood clotting that is used to help determine Coumadin dosage.
Without adequate vitamin K, however, prothrombin and other Gla proteins cannot be activated and thus are unable to hold onto calcium and carry out their regulatory roles—not only in blood coagulation but also in the bones, vascular system, and other tissues. And that’s where the trouble begins.
The Calcium Paradox
Calcium, as you know, is an essential mineral. More than 99 percent of your body’s calcium is located in your bones, where it provides strength and structure. The remaining 1 percent is involved in muscle and blood vessel contraction, hormone and enzyme secretion, and other functions.
But calcium has a dark side. It may also be deposited in the walls of the arteries, causing them to narrow and lose elasticity, which hampers blood flow and raises blood pressure. It can accumulate in the coronary arteries and heart valves, increasing risk of heart attack and valve calcification. Calcium can also build up in the soft tissues of the joints, kidneys, and other organs, and there is even speculation that excessive levels of intracellular calcium may predispose you to some types of cancer.
This is the calcium paradox. Bottom line, you want calcium to stay in your bones and out of your soft tissues. Some suggest that a high calcium intake is problematic, and a few studies have linked high consumption with increased risk of heart attack, cancer, and other diseases. But excess calcium is not the problem. It’s vitamin K deficiency. If you’re not getting enough of this crucial vitamin, Gla proteins are unable to escort calcium out of the soft tissues and into the bones where it belongs.
Vitamin K Moves Calcium Out of the Arteries
The most exciting new research on vitamin K focuses on its role in cardiovascular health. At the Linus Pauling Institute’s recent conference in Portland, OR, Leon Schurgers, PhD, senior scientist at the University of Maastricht in the Netherlands, gave a compelling talk entitled, “Vitamin K: The Clotting Vitamin That Became Omnipotent.”
He presented information about matrix Gla protein (MGP), a potent inhibitor of soft tissue calcification that is synthesized in the blood vessel walls. MGP protects the arteries against calcium buildup (arteriosclerosis, or hardening of the arteries), which is a risk factor for cardiovascular disease. Before MGP can exert its calcium-binding mechanisms, however, it must first be “turned on” by vitamin K.
Dr. Schurgers discussed results of the Rotterdam Study, a clinical trial involving nearly 5,000 older Dutch men and women, in which strong correlations between vitamin K intake and cardiovascular disease were discovered. Study participants with the highest consumption had 50 percent reductions in arterial calcification and death from cardiovascular disease, and a 25 percent decline in overall mortality.
If You’re on Coumadin, Listen Up!
Dr. Schurgers also shared disturbing—but hopeful—research on Coumadin, the popular blood-thinning drug, and its interaction with vitamin K. If you’re taking this drug, pay attention, because what I’m about to tell you defies conventional wisdom.
People who take Coumadin are often told by their doctors to go easy on broccoli, greens, and other foods that contain vitamin K. The reasoning is that because vitamin K is the “clotting vitamin,” it counteracts Coumadin’s therapeutic effects. However, the inevitable vitamin K deficiencies can have disastrous effects. Studies show that people who take Coumadin have a twofold increased risk of arterial and heart valve calcification within just three years of starting the drug! (Not surprisingly, they also have an increased risk of osteoporosis.)
However, taking a modest amount of supplemental vitamin K may protect against these adverse effects. In Dr. Schurgers’ animal studies, vitamin K not only blocked but actually reversed Coumadin-induced arterial calcification. A handful of small human studies demonstrate that vitamin K also stabilizes Coumadin’s anticoagulant effects and helps maintain consistent therapeutic blood levels.
Additional studies are underway, but in the meantime, if you’re on this drug, talk to your doctor about taking supplemental vitamin K while keeping close tabs on your INR. Be aware that he may not yet be familiar with this research, so be sure to share the starred references on page 6, which explain and support this recommendation.
From Bones to Cancer
Vitamin K, as I mentioned, is also involved in bone metabolism. It activates another Gla protein called osteocalcin, which “cements” calcium into the bone. Deficiencies are clearly linked with low bone density and increased risk of fracture. Japanese women who eat lots of vitamin K–rich natto (a fermented soy food) and American women with high intakes of K-dense leafy greens have stronger bones than their peers who don’t eat much of these foods. Studies also show that supplemental vitamin K protects postmenopausal women against fracture risk.
Supplemental vitamin K may also reduce insulin resistance. In a 2008 study, men who took daily vitamin K supplements, along with a multivitamin, calcium, and vitamin D, had significantly slower progression of insulin resistance than those whose regimens did not include vitamin K.
Early research suggests that vitamin K also retards the development of rheumatoid arthritis and facilitates the healing of fractures. It benefits patients with chronic kidney disease, who have high rates of vascular calcification and cardiovascular death. It may even protect against some types of cancer. German researchers published data last year showing that men who consumed the most vitamin K were 63 percent less likely to develop advanced prostate cancer.
K1 Versus K2
Vitamin K is actually a group of fat-soluble compounds divided into two primary groups: K1 and K2, and they’re not exactly the same. K1 is abundant in broccoli, kale, chard, and other leafy greens; there’s also a little in olive and vegetable oils. K2 is found in fatty meat, egg yolks, and fermented products such as cheese, sauerkraut, and natto (by far the richest source), plus it is synthesized by bacteria in the large intestine. Although Americans get more dietary K1, it’s poorly absorbed. K2, on the other hand, is taken up rapidly.
These two types of vitamin K also have somewhat different physiological actions. K1 is more active in clotting, while K2 is the preferred form in the soft tissues and bones. In the Rotterdam study mentioned above, vitamin K2 intake reduced risk of arterial calcification, heart attack, and death, while K1 consumption had no protective effect. K2 is also the form that has been shown in animal studies to protect against Coumadin-induced vascular calcification.
Kick Up Your K Level
So, how do you increase your levels of this vitamin? For starters, beef up your dietary intake, especially of vitamin K2. But be aware of factors that may contribute to vitamin K deficiencies. Intestinal problems such as celiac disease and ulcerative colitis hinder absorption, as do very high intakes of vitamin A—the two vitamins compete for absorption. A number of drugs also deplete vitamin K levels, including broad-spectrum antibiotics, salicylates, and Questran and related cholesterol-lowering drugs.
That leaves nutritional supplements. Both K1 and K2 are available in supplement form, and each has its merits. Vitamin K1 is used in the injections most newborns receive shortly after birth to prevent hemorrhage, as well as in many bone formulas. And for years, it was the only vitamin K supplement available.
But vitamin K2 is gaining in popularity. Dr. Schurgers is excited about a newer form of K2 called menaquinone-7 (MK-7). This natural compound, derived from natto, has a much longer half-life, meaning it stays in the body longer. Therefore, when taken just once a day and at lower doses, more stable blood levels can be attained. (Don’t confuse it with the synthetic MK-4 form of vitamin K2. MK-4 has a short half-life and thus requires larger doses that must be taken multiple times a day. Because of this, it may interact adversely with Coumadin.)
The “Omnipotent” Vitamin
I guarantee you’ll be hearing much more about vitamin K in the future. Studies suggest that this vitamin may also help patients with cystic fibrosis, reduce risk of varicose veins, discourage kidney stone formation, and dampen inflammation—to mention just a few of the research frontiers. It also appears to enhance some of the therapeutic effects of vitamin D.
As you can see, I’m very enthusiastic about safe, inexpensive, “omnipotent” vitamin K. I’ve made it part of my daily supplement regimen, and I urge you to consider doing the same
From: Health & Healing with permission from Healthy Directions, LLC. Photocopying, reproduction, or quotation strictly prohibited without permission from the publisher. To subscribe to Health & Healing, click here.