Vitamin K and bone health (part 1)

The idea of using nutritional supplements to prevent diseases has been gaining currency over the past several years. For osteoporosis, vitamin K has been getting a lot of attention because of its role in bone health. But can vitamin K supplements actually prevent osteoporosis? In a review article published recently in the Journal of Clinical Densitometry, our nutrition expert, Dr. Maryam S. Hamidi along with Dr. Gajic-Veljanoski, our clinical epidemiologist, and Dr. Cheung , a professor of medicine and the director of our program, survey the existing research literature on vitamin K and its effects on bone health. 

Background on vitamin K

Vitamin K is a fat-soluble vitamin that plays different roles in our bodies but  is mostly known for its role in blood coagulation.*

Vitamin K is not just one substance. It represents a group of compounds that are chemically very similar. There are two main forms of vitamin K — vitamin K1 and vitamin K2. Vitamin K1 is made by plants and is also the form of vitamin K that is most present in our diets. The main sources of vitamin K1 include green leafy vegetables, broccoli, brussel sprouts, avacado, kiwi, green grapes, some herbs, and green and herbal teas. Vitamin K2 further represents many different forms of vitamin K, known as menaquinones (MK-n). MK-4 to MK-10 are  the main forms of vitamin K2 that we get in our diet from foods from animal sources or fermented products.  Dietary sources of MK-4 include fish, eggs, liver, kidney, milk, butter, and fermented cheese or vegetables. Although vitamin K1 is the form we ingest mostly, MK-4 is the form of vitamin K that is most present in our bodies, leading some researchers propose that vitamin K1 is being converted in our bodies to MK-4.

Vitamin K and bone function

Vitamin K is involved in three broad areas of bone health:

• vitamin K helps calcium get into bone
• vitamin K is required for osteocalcin, an important bone protein, to function during bone formation
• vitamin K may also be involved in maintaining bone strength

Research on vitamin K, bone density, and fractures

Our knowledge on how vitamin K affects bone health comes from two types of studies — observational studies and clinical trials. In part 2, we will summarize the latest research on vitamin K and osteoporosis and whether current research supports the idea of taking vitamin K supplements for osteoporosis prevention.

*Contrary to general belief, getting too much vitamin K from diet does not cause blood clots in healthy people who are not taking blood thinning medications. That said, vitamin K reduces the effectiveness of blood thinning medications and people who take such medications should monitor their intakes of vitamin K to avoid blood clotting complications.

Reference: Hamidi MS, Gajic-Veljanoski O, Cheung AM. Vitamin K and Bone Health. J Clin Densitom 2013;16(4):409-13. doi: 10.1016/j.jocd.2013.08.017.