December 19 2008 post. Premise: my interest in most vitamins, except for vitamin D and (occasionally) a few others, has always been marginal. I also do not take a multivitamin or any individual vitamins.

 

Recently, though, I happened upon a Japanese study on vitamin K and myeloma: http://tinyurl.com/4tg824. I had already read about vitamin K on Don’s “Myeloma Hope” blog. But what this particular study revealed was news to me. As follows:

 

Vitamin K inhibits the growth of myeloma cells.

 

Before taking a look at the study, though, what is vitamin K, and can we obtain it from our diet? It’s a fat-soluble vitamin known as the “clotting” vitamin (the “K” in fact derives from the German word Koagulation), because our blood would not clot without it. (Note: warfarin, or Coumadin, is a vitamin-K antagonist because it inhibits coagulation.)

 

There is a lot of helpful but very technical information on the Linus Pauling Institute website: http://tinyurl.com/33dlfy

 

A few observations. Vitamin K is essential for the health of our bones. One of the consequences of vitamin K deficiency is, in fact, a reduction in osteoblast, i.e. bone-building, activity (see the LP Institute’s “Disease Prevention” section). And, surprise surprise!, I read that vitamin K deficiencies frequently occur in multiple myeloma patients. Hah.

 

Our bodies are unable to store vitamin K for long periods of time or in large amounts, which is why it is crucial to eat foods that contain it (unless you are taking warfarin). Vitamin K is present in cabbage, kale, broccoli, cauliflower, spinach and leafy vegetables in general. A partial vitamin K food list can be found on the LP Institute website (scroll down to “Sources”).

 

Interesting excerpt: To consume the amount of vitamin K associated with a decreased risk of hip fracture in the Framingham Heart Study (about 250 mcg/day), an individual would need to eat a little more than 1/2 cup of chopped broccoli or a large salad of mixed greens every day. Well, that’s not too difficult!

 

 

Okay, let’s go back now to the Japanese study that I mentioned at the beginning of the post. It examines the effect of vitamin K2 (aha!) specifically on myeloma cells. Previous studies showed that vitamin K2 can kill cell lines derived from patients with myelodysplastic syndrome (MDS) and acute leukemia, as well as freshly isolated leukemic cells.

 

An excerpt from the study’s Discussion: VK2 may be a good candidate therapeutic agent for myeloma patients since it caused growth inhibition, induced apoptosis via the mitochondrial pathway, activated apoptosis-inducing p38 MAPK,37-39 and generated reactive oxygen species.

 

Another important result was that vitamin K2 and dexamethasone were found to work synergistically against myeloma cells. And, by the way, the study mentions our old enemy, Bcl-x. When exposed to vitamin K2, Bcl-x was reduced. Hah!

 

Before filling up on vitamin K2, though, we should know that high doses could cause adverse effects such as thromboembolic events. This is of particular clinical relevance, because it is now recognized that thalidomide leads to increased rates of thromboembolic events in MM patients, especially when used in combination with other anti-myeloma agents (e.g., dexamethasone or alkylators). Therefore, if VK2 were to be used clinically as one of the therapeutic agents, it would have to be started at a low dose and with meticulous care to avoid thrombotic events.

 

Final considerations. The researchers point out that these were in vitro experiments done at high-dose concentrations for short periods. The long-term effects of vitamin K2 are not known. However, they add, supplementation with vitamin K2 might be useful in the treatment of elderly patients or patients who are unable to undergo harsh conventional treatments.

 

I will not take a vitamin K supplement, but I will print the WHF chart of vitamin K food sources and hang it up in my kitchen…just to make sure now and again that my vitamin K intake is adequate. I am so glad I did this bit of research today!