With the growing awareness of the importance of vitamin D to health, many people are taking high dose supplemental vitamin D. Unfortunately this may be doing more harm than good to some individuals, particularly those low in vitamin K. These people may be unknowingly increasing their risk for blood vessel calcification, kidney stones and other manifestations of soft tissue calcium deposition. It is becoming increasingly clear that individuals taking large doses of vitamin D need to get their vitamin K levels checked or risk serious consequences.

The Vitamin D & Vitamin K connection

Vitamins D and K work in concert to control the use of calcium by the body. Vitamin D is vital for proper absorption of dietary calcium and retaining it in the kidneys. It helps maintain proper calcium levels in the blood for bone health and proper cell function relating to calcium homeostasis.

Vitamin K helps the body put the calcium in the appropriate places in the body, like bone. If there is not adequate vitamin K available, blood calcium tends to find its way into places besides bone. Recent research is finding this is exactly what is happening.

Measuring Vitamin K 

There is a new way of measuring whether the body has enough vitamin K available. It is a “functional” assay because, rather than measuring vitamin K levels directly (which is not a good measure of adequacy), it measures the biochemical activity vitamin K is involved in. If vitamin K is in adequate amounts, the biochemical activity functions properly. Measurement of blood levels of undercarboxylated (UC) osteocalcin (OC) is one such functional test. It is now available to the public. Vitamin K “carboxylates” the bone protein OC. When this happens, OC can then add calcium to bones. If there is not enough vitamin K present, the amount of “undercarboxylated” OC goes up in the blood. See, "The Many Functions of Vitamin K."

With all the interest in vitamin D and the revelations of all the good things it does for the body, many people will be taking large doses for years to come. I think what we will see developing in the future are signs of soft tissue calcium deposition due the low vitamin K levels. This is already being seen in the medical literature and researchers are finding vitamin K deficiency is more common than once thought. 

Sources of Vitamin K

The primary sources of vitamin K are the gut bacteria (they manufacture it) and green vegetables. If you don’t eat your veggies or if you take antibiotics, you could be in for trouble dosing with vitamin D.