Natural Foods Merchandiser

Find out what's so special about vitamin K

by Jack Challem

Long recognized for its role in blood clotting, conventional physicians view vitamin K with caution. That's because excess vitamin K interferes with the activity of Coumadin and related anti-coagulant drugs, which are often prescribed after a heart attack, stroke or heart surgery.

But research shows that vitamin K has other roles in health, such as maintaining bone mass and reversing osteoporosis. Recent research also demonstrates that vitamin K may indirectly influence glucose tolerance, a finding that could shift dietary management of diabetes. But, there's more than one type of vitamin K—and the varieties may actually have different roles in the body.

Several types of vitamin K
Vitamin K1 refers to a single compound, phylloquinone, found in leafy green vegetables. In contrast, vitamin K2 refers to a family of related nutrients known as menaquinones, which are found in meats, dairy, eggs and other foods. One of the most researched members of the K2 family is MK-4.

The research
Most recent research has focused on MK-4. • Bone health. The body needs Vitamin K to synthesize osteocalcin, a protein secreted by bone cells. In turn, osteocalcin helps regulates calcium activity in bone.

In separate studies, Dutch and Japanese researchers used relatively large amounts of vitamin K2—45 milligrams daily—to treat and reverse osteoporosis in women (Osteoporosis International, 2007; Gynecological Endocrinology, 2006). A meta-analysis of seven studies, published in the 2006 Archives of Internal Medicine, found that high-dose vitamin K2 supplements reduced bone fractures in women by more than 60 percent.

  • Heart disease. Vitamin K2, but not K1, blocks the calcification of arteries, which helps maintain more youthful and flexible blood vessels (Journal of Vascular Research, 2003). Theoretically, Coumadin and other anti-coagulant drugs could increase arterial calcification.
  • Cancer. Researchers used either 45 milligrams of vitamin K2 with conventional medical modalities, or conventional modalities alone, to treat 40 women with viral cirrhosis of the liver for eight years. During the study, only two of the 21 women receiving vitamin K2 developed liver cancer, in contrast to nine of 19 women who did not receive the vitamin (Journal of the American Medical Association, 2004).
  • Diabetes. A 2006 study published in Cell reported that osteocalcin also functions as a hormone that regulates the number of insulin-producing cells in the pancreas, the secretion of insulin, sensitivity to insulin and the size of fat cells. Because osteocalcin production depends on vitamin K, this study suggests the vitamin may play an important role in preventing and treating diabetes. More research is under way.

    How to use vitamin K
    Although some research shows benefits in bone health from vitamin K1 supplements, vitamin K2 seems to be far more biologically active and effective in preventing and reversing osteoporosis and other health problems. Consider 5 milligrams daily of vitamin K2 a preventive dose and 45 milligrams daily a therapeutic dose.

    Retailer tips
    When advising customers, remember two more points about vitamin K2 and anti-coagulant drugs such as Coumadin:

  • Always ask your customer whether he or she is taking an anti-coagulant. Vitamin K supplements will reduce the drug's effectiveness and may result in life-threatening blood clots.
  • A recent study found that vitamin K provides greater anti-coagulant stability, as long as the Coumadin dose is adjusted upward accordingly. This adjustment is best left to a knowledgeable physician (Journal of Thrombosis and Haemostasis, 2007). Jack Challem is a personal nutrition coach in Tucson, Ariz. His latest book is The Food-Mood Solution (Wiley, 2008).

    Natural Foods Merchandiser volume XXVIII/number 9/p. 38

  • Hide comments


    • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

    Plain text

    • No HTML tags allowed.
    • Web page addresses and e-mail addresses turn into links automatically.
    • Lines and paragraphs break automatically.