The vitamin K family and bone health

The holidays are that time of year for family gatherings. Some of us have big families while some of us have small families. The much ignored(until recently) vitamin K is actually a big family and not just one lonely vitamin. In this respect, it is similar to the B vitamin complex, which is made up of several distinct vitamins under the vitamin B umbrella, all of which are needed for proper energy metabolism.

So what is so special about vitamin K? Vitamin K, which is fat-soluble, is essential for blood clotting(coagulation), as well as optimal calcium metabolism. A deficiency of vitamin K can lead to excessive bleeding. Unfortunately for vampires, vitamin K deficiency is rare.

Phylloquinone chemical structure

Menaquinone chemical structure

There are two main forms of vitamin K – vitamin K1(phylloquinone), and vitamin K2(menaquinone). Vitamin K1 is found mostly in plants while vitamin K2 is found more in meat and produced in the body. This gets even more fun when you consider that there are also many sub-forms of menaquinone, which seem to have somewhat different effects. The overall effect of vitamin K is the synthesis of proteins needed for proper coagulation and the proper metabolism of calcium and bone tissue. This makes vitamin K important both for bone growth and maintenance, as well as the prevention of arterial calcification.

According to Schurgers LJ, Cranenburg EC, Vermeer C. at Maastricht University:

Among the proteins involved in vascular calcium metabolism, the vitamin K-dependent matrix Gla-protein (MGP) plays a dominant role. Although on a molecular level its mechanism of action is not completely understood, it is generally accepted that MGP is a potent inhibitor of arterial calcification. Its pivotal importance for vascular health is demonstrated by the fact that there seems to be no effective alternative mechanism for calcification inhibition in the vasculature. An optimal vitamin K intake is therefore important to maintain the risk and rate of calcification as low as possible.

So vitamin K looks very promising as a treatment for calcification of the arteries(a very common problem among the elderly). Basically, the vitamin K family ensures calcium goes where it belongs(the bones), so it doesn’t get stuck where it can cause problems(the arteries).

According to the same vitamin K researchers quoted above:

Prolonged sub-clinical vitamin K deficiency is a risk factor for osteoporosis, atherosclerosis, and cancer. Present recommendations for dietary intake are based on the daily dose required to prevent bleeding. Accumulating scientific data suggests that new, higher recommendations for vitamin K intake should be formulated.

It also appears that vitamin K may help prevent osteoporosis, and surprisingly, cancer. It also says the scientific data suggests new, higher recommendations for vitamin K intake. It doesn’t say exactly how much more, and I am not recommending we all take vitamin K pills. However, if you are at risk for osteoporosis or have atherosclerosis(of which calcification of the vessels plays an important part), it may be a good idea to talk with your doctor about vitamin K.

Vitamin K is also associated with a decreased risk of type 2 Diabetes, according to Diabetes Care:

This study shows that both phylloquinone and menaquinones intakes may be associated with a reduced risk of type 2 diabetes.

So how can you be sure you are getting enough of both forms of vitamin K? Eating a varied diet that includes a lot of green leafy vegetables can help ensure you get enough. Vitamin K is also produced by gut bacteria. So eating fermented food may ensure optimal vitamin K levels. People with chronic gastrointestinal diseases are at a much higher risk for vitamin K deficiency, according to – Am J Clin Nutr. 1985 Mar;41(3):639-43.

Here is some interesting research from Italy on the different biological effects of the various forms of vitamin K:

Vitamin K (vitamin K1 or phylloquinone and vitamin K2, a series of menaquinones [MKs]) is involved in the production of bone and matrix amino acid γ-carboxy-glutamic acid (Gla) proteins, regulating bone and vascular calcification. Low vitamin K concentrations are associated with increased risks of fractures and vascular calcification, and frequent complications in hemodialysis patients. We carried out an observational study to establish the prevalence of vitamin K deficiency and to assess the relationship between vitamin K status, vertebral fractures, vascular calcification, and survival in 387 patients on hemodialysis for ≥1 year. We determined plasma levels of vitamin K compound, bone-Gla-protein, matrix-Gla-protein, and routine biochemistry. Vertebral fractures (reduction in vertebral body height by ≥20%) and aortic and iliac calcifications were also investigated in a spine (D(5) -L(4)) radiograph. Three-year patient survival was analyzed. Important proportions of patients had deficiency of MK7 (35.4%), vitamin K1 (23.5%), and MK4 (14.5%). A total of 55.3% of patients had vertebral fractures, 80.6% had abdominal aorta calcification, and 56.1% had iliac calcification. Vitamin K1 deficiency was the strongest predictor of vertebral fractures (odds ratio [OR], 2.94; 95% confidence interval [CI], 1.38-6.26). MK4 deficiency was a predictor of aortic calcification (OR, 2.82; 95% CI, 1.14-7.01), whereas MK5 deficiency actually protected against it (OR, 0.38; 95% CI, 0.15-0.95). MK7 deficiency was a predictor of iliac calcification (OR, 1.64; 95% CI, 1.03-2.60). The presence of vertebral fractures was also a predictor of vascular calcifications (OR, 1.76; 95% CI, 1.00-3.08). Increased alkaline phosphatase and C reactive protein (CRP), age, and cerebrovascular events were predictors of mortality. Our study suggests that the vitamin K system may be important for preserving bone mass and avoiding vascular calcification in hemodialysis patients, pointing out a possible role of vitamin K in bone and vascular health. Based on our results, we suggest that the general population should also be studied for vitamin K deficiency as a possible cause of both vertebral fractures and vascular calcification.
Copyright © 2012 American Society for Bone and Mineral Research.

So, have you figured out yet which is your favorite form of vitamin K? Don’t stress yourself out over whether or not you are getting enough of the MK7 form of vitamin K or enough phylloquinone. If you don’t have liver problems, or gastrointestinal problems, or if you are not on dialysis and you are young, eat right and get plenty of exercise, you have little to worry about. But if you are at risk for diabetes, osteoporosis or atherosclerosis, speak with your doctor about vitamin K.

Vitamin D may improve athletic performance

It may not be the cold air or Old Man Winter’s roar that keeps even seasoned athletes indoors during the winter. According to the scientific literature, vitamin D may improve athletic performance, but only in athletes who are deficient in vitamin D.

So who is most likely to be deficient in vitamin D? Since vitamin D is produced in the body when the skin is exposed to sunlight, it shouldn’t worry people who get at least some sun exposure throughout most of the year, unless they live north of 37 degrees latitude during the winter. The sun’s rays are too weak north of 37 degrees, and it’s even worse if your skin is dark, since melanin can block sunlight.

The elderly also have problems making vitamin D, even if they get sufficient sunlight. Vitamin D(a misnomer, it is actually a hormone) is necessary for calcium absorption, which helps build strong bones, and may also boost the immune system, among other things. Scientists have found links between vitamin D deficiency and certain forms of cancer, but a lot more research needs to be done.

Eating a healthy, varied diet can provide just about all the nutrients the average person needs, but hardly any foods contain sufficient quantities of vitamin D to meet new nutritional guidelines. Even multivitamins fall short of the new guidelines. So it looks like eating food fortified with vitamin D(like milk) or vitamin D supplements may be the answer, for those who live north of 37 degrees latitude from autumn to spring.

A rather interesting possible solution which doesn’t involve supplements is to get some mushrooms(button mushrooms, shiitake, and many other mushroom species, but do not pick any wild mushrooms unless you know what you are doing) and place them in the sun for a few hours. When exposed to sunlight, they will manufacture vitamin D, just like humans, in quantities that are as good as or even better than supplements. This is certainly a wild solution!

I take a 5,000 I.U vitamin D supplement about twice a week during the winter since I am in the north-east U.S. I don’t take them at all during the summer, since I get enough sunlight during that time of year. I take it twice a week since vitamin D is fat-soluble, which means it can be stored in the liver and fatty tissue, unlike water soluble nutrients like vitamin C, which are quickly removed from the body which is why you need to get it every day.

So if you’re an athlete or even if you’re not an athlete, and you feel sluggish and you live in the northern U.S, see if you can get your vitamin D levels checked by your doctor. Or, you can just eat more mushrooms that have been sun-bathed as suggested above if you suspect you’re deficient. Like many nutrients, Vitamin D can be toxic in large quantities, so be careful.

For my fellow vegetarians and vegans – vitamin D-3, also called “cholecalciferol” is not vegan since it is derived from animal sources. However, vitamin D-2, also called “ergocalciferol” is vegan since it comes from plant sources. The type of vitamin D that is in mushrooms is D-2/ergocalciferol.