Ask the Pharmacist

Q) I read somewhere that having low levels of vitamin K might increase my risk of early death. I have never heard of vitamin K before; What exactly is it and how do I prevent being deficient in it?

A) Most people are familiar with vitamins A, C and E but less so with vitamin K. Compared to the others, its role in your body and possible therapeutic benefits are more obscure.

This however may be changing as research first published in the June 2020 issue of the American Journal of Clinical Nutrition is gaining a little traction with the mainstream media making this vitamin more and more difficult to ignore. In this paper, researchers looked at approximately 4,000 adults aged 54 to 76 who were involved in three studies.

The researchers looked at essentially two data points. One was their blood levels of vitamin K and the other was their rate of heart disease or death over the next 13 years. It should be noted that prior to the start of the analysis, all participants were judged to be free of heart disease.  While the results showed no definitive link between vitamin K and the incidence of heart disease, researchers did note that those people with the lowest levels of vitamin K were 19% more likely to die during the study period when compared to those with adequate levels.

While the reason for this possible link remains unknown, scientists are familiar with the ability for vitamin K to prevent calcium buildup in our bleed vessels. Blood vessel calcifications are mineral deposits that build up on the walls of our arteries and veins causing these vessels to harden and become narrower decreasing the amount of blood flowing through them and forcing our heart to work harder in order to try and maintain an adequate blood supply. These resultant damaged blood vessels are unquestionably associated with an increased risk of suffering a cardiovascular accident such as a heart attack.

The hypothesis behind these significant results is that vitamin K is known to activate a protein in our body known as Matrix Gia (MGP). Activated MGP binds calcium circulating within our bloodstream thereby protecting our vessels from this damaging calcification. However, a deficiency in vitamin K results in inadequate MGP activation and therefore a greatly impaired calcium removal process. This study corroborates an earlier observational study based in Rotterdam that showed a high dietary intake of vitamin K reduced arterial calcification by 50%, overall cardiovascular risk by 50% and all-cause mortality by 25%. These are far from insignificant numbers!

And yet while we once thought most people had abundant levels of vitamin K circulating through their bodies, new research indicates this may not in fact be true. Guidelines for an adequate intake vary according to age and gender (and different countries have slightly different recommendations) but it is generally accepted that women over the age of 19 should aim for 90mcg of vitamin K daily and men of the same age group should strive for 120mcg a day.

The same researchers who conducted this study found that, according to their survey results, more than 60% of men aged 70 and older (who are, perhaps not surprisingly, our highest risk group for cardiovascular incidents) do not hit these dietary markers. This may not be incredibly shocking when one considers the best sources of this vitamin. While meat, cheese and eggs are on this list, the very best sources of vitamin K are found in green leafy vegetables such as spinach, kale broccoli and lettuce, vegetable oils and some fruits such as blueberries and figs.

Vitamin K actually comes in 2 forms conveniently called vitamin K1 (phylloquinone and phytonadione) and vitamin K2 (menaquinone-4 and menaquinone 7). It is understood that the K2 form brings the heart health benefits but vitamin K’s role in our body is not simply limited to our cardiovascular system, It also plays a strong role in our bone health. Some research has shown (“some” is used intentionally as it is a near impossibility to get a consensus on anything when it comes to nutrition or the use of dietary supplements) that people who eat more vitamin-K rich foods are less likely to suffer a hip fracture than others. A few studies (but not all) have also found that taking a vitamin K supplement can improve bone strength and reduce the risk of breaking a bone.

Vitamin K has not been shown to be harmful but those who take the blood thinner warfarin (Coumadin) need to ensure they maintain a relatively stable intake of vitamin K foods as sudden increases or decreases in their consumption could drastically alter the blood levels of this drug putting their health in serious jeopardy.

There are also certain drugs that can put you at risk of being deficient in vitamin K such as the bile acid sequestrants cholestyramine or colestipol which are used to reduce cholesterol levels or treat chronic diarrhea. As well, people who are on antibiotics for more than a few weeks may be lacking in vitamin K as well as these drugs can destroy the good bacteria in your gut that is essential in making our own supply of vitamin K.

While it is preferable for people to get their vitamins and minerals from “real” food, vitamin K is available in supplements both by itself, in many of the daily multivitamin formulations and sometimes paired with other nutrients such as calcium, magnesium and/or vitamin D.

So, do your heart a favour and add a hearty serving of kale to your plate. Strive for those greens to fill half of your plate! If you are struggling with recipes to incorporate these vitamin K rich roods into your diet, we would be happy to share some. For more information about this or any other health topics, contact your pharmacist.