- Vitamin K refers to a few molecules that exert cardioprotective and bone-forming benefits.
- Vitamin K supplementation is one of the few supplements that’s ever been linked with reducing death from all causes.
- It’s a good idea to take 500 mcg vitamin K (as K1) or 250 mcg MK-7 per day either from a multivitamin or as a standalone supplement.
Out of all the 24 essential vitamins and minerals, not many need to be supplemented.
I mean, how many readers have done their research on minerals like copper and phosphorus? Most people may not even realize that manganese isn’t a typo of magnesium.
Out of all 24 essential vitamins and minerals one of the few that should be supplemented are vitamin D and, perhaps, zinc and magnesium for athletes. If you’re not athletic and you have a mixed diet with plenty of vegetables then you can drop those minerals as well.
However, recently (past few years) there has been discussion as to whether or not vitamin K could join vitamin D in this niche. They have many similarities:
- They’re both essential to preventing disease states.
- They’re abundant in food, at least when it comes to getting enough to prevent a disease state from occurring.
- True deficiency is rare, but most people fall shy of what scientists think is an optimal intake that’s a few times higher than the RDA.
- This higher, optimal intake is difficult to attain through food and so supplementation becomes the next best option.
The major difference is how they affect the body. With vitamin K you don’t get a wide range of benefits but, what vitamin K benefits, it really benefits—it may be the one supplement to actually reduce your risk of dying.
So on that note, let’s learn more about it, shall we?
- What Is Vitamin K?
- What Does Vitamin K Do?
- The Top 3 Vitamin K Benefits
- Vitamin K and Cardiovascular Disease
- Vitamin K and Bone Health
- Vitamin K and Exercise
- What Does Vitamin K not Do?
- Vitamin K and Cholesterol
- Vitamin K and Bruising
- Vitamin K and Weight Loss
- What Is the Clinically Effective Dosage of Vitamin K?
- What Are the Most Common Vitamin K Side-Effects?
- Should You Take Vitamin K Supplements?
- The Bottom Line on Vitamin K
Table of Contents
Vitamin K initially referred to the molecule called phylloquinone, which was found to be a vitamin required by human diets. Failure to consume vitamin K leads to excessive bleeding as, in reference to its namesake, it is involved in koagulation (the Germans discovered it, as always).
However, after its initial discovery more molecules have been discovered that can help the body in this manner. They have all been classified as vitamin K2, with phylloquinone being given the title of vitamin K1 because it was discovered first.
Vitamin K1 is classically known as the plant-based source of vitamin K. There’s only one vitamin K1 and it works well while serving as a reference for the other forms of vitamin K.
Vitamin K2, rather than being called phylloquinone, is called a menaquinone. There are many of them in a series, ordered by the number of what are called “isoprene” groups (or how long the molecule’s tail is) and numbered accordingly.
For example, one of the most common forms of menaquinone has four isoprene groups, so it’s called MK-4 (aka. Menaquinone vitamin K-4). MK-7 is another menaquinone with a slightly longer tail, and all the other menaquinones are not common supplements.
There’s also a potential “vitamin K3,” aka menadione, which is just a form of vitamin K with all isoprene groups removed. This isn’t used as a supplement so we’ll ignore it for this article.
So to summarize, the term “vitamin K” is an umbrella term for the vitamers K1, MK-4, and MK-7. All of these can be viable but are a bit different from each other, but will henceforth collectively be referred to as “vitamin K” unless otherwise specified.
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Vitamin K works through a group of vitamin K-dependent proteins.
“Vitamin K-dependent protein” refers to any protein that, in order to exert its actions in the human body, needs a molecule of vitamin K to help—think of vitamin K being the tool that the protein needs to do its job.
With a sufficient vitamin K intake, these proteins can carry out their required functions in the human body. With insufficient intake they can’t work optimally, and supplementing extra vitamin K can optimize these functions since more proteins have their tools.
There are many vitamin K-dependent proteins but the most important ones, or at least the most researched ones, are:
- Prothrombin and related clotting proteins, their actions being why vitamin K is called a vitamin and helps with blood clotting.
- Osteocalcin, which reduces soft tissue calcification (prevents arteries from becoming hardened).
- Matrix GLA protein (aka MGP) which aids in bone growth.
These ones are most important since we know how supplementation affects them, and their actions seem to be the relevant ones in human studies.
Now, what exactly are these benefits? Let’s investigate.
The top benefits of vitamin K are all due to interacting with it’s proteins, and are:
- Improved cardiovascular health.
- Improved bone health.
- Cardiovascular exercise capacity.
The major benefit of vitamin K, which by itself is enough to warrant supplementation, is improved cardiovascular health.
Sometimes calcium can get deposited on blood vessels, hardening them and making them less able to adapt to blood flow. Normally this leads to an increase in cardiac events, but vitamin K can reduce this process.
Levels of calcium on the arteries are an independent risk factor for death by cardiovascular disease, and all cause mortality even among young adults—basically, excessive levels of arterial calcium are bad for everybody regardless of goals, diet, or demographics.
MGP is the most potent vitamin K-dependent protein that can remove calcium from arteries, although osteocalcin can also do this. Supplementation of vitamin K can increase the activity of MGP, which is thought to be why long term vitamin K supplementation can reduce calcification.
There’s still a few questions floating around as to the mechanisms of how vitamin K reduces calcification, since sometimes calcification is reduced even if MGP isn’t affected (and cancer patients may also have their lives extended a bit with vitamin K).
However, the fact vitamin K may reduce all cause mortality is pretty damn notable and alone should warrant supplementation.
Vitamin K supplementation, at some dose, is prudent for a long and healthy life as it seems capable of reducing cardiovascular death and death overall across all demographics.
Vitamin K is highly synergistic with vitamin D in regards to maintaining proper bone health. This is in part due to their diverging roles.
Vitamin K, via osteocalcin, plays a major role in bone maturation—not necessarily growth, which means that it’s more likely to play a role in bone mineral density rather than overall size. As vitamin D helps with bone growth, the two complement each other.
Given how vitamin K has the role of strengthening the bone, we see that reflected in human studies on the topic as vitamin K supplementation is associated with significantly less fractures in the elderly (due to falls). Even if your bones don’t grow, they may become a bit stronger.
Studies on bone mineral density and bone loss, however, are mixed.
Some studies using MK-4 at 1.5 mg per day have found a reduction in bone loss, which has also been observed with MK-7 (375 mcg) so there’s some positive data, but it’s met by a few failures of vitamin K to reduce bone loss on it’s own.
It seems that if you want to use vitamin K for protecting your bones then, while it can work on its own, it would be best to pair it with vitamin D and perhaps some calcium in the diet.
Alternatively, there are a collection of studies using MK-4 showing that supplementation in older women is able to not only reduce further bone losses but may increase bone mass—this relatively rapid benefit is seen at astonishingly high doses of 40 to 45 mg a day. However, this is an obscenely high dose given how microgram dosages are effective.
Vitamin K is similar in concept to vitamin D when it comes to bone tissue. Just take it every day, perhaps in your multivitamin, and it will pay off in the long term.
A lesser known benefit, yet an intriguing one—vitamin K may help exercise capacity.
The study in question found that taking 300 mg of K2 for four weeks and then reducing it to 150 mg for another four weeks was able to increase cardiac output by 12%.
Cardiac output is the ability of the heart to pump blood throughout the body (usually measured in a “liters per minute” measurement) and increasing cardiac output means either the heart is stronger or the vessels more accomodating of flowing blood.
More research is needed to understand exactly how vitamin K is doing this but it’s thought to strengthen the heart tissue itself.
Vitamin K and its benefits to the heart may also extend to cardiovascular exercise.
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If there’s one difference between vitamin K and D, practically speaking, it would be that people don’t run around claiming vitamin K is a panacea. What it does, it does well, but it can only do a few things. As such, it has failed to:
- Have any effect on other parameters of cardiovascular health.
- Have any effect on bruising when used as a skin cream.
- Have any effect on body weight management.
Despite it being known as a cardiovascular health supplement, vitamin K does not influence cholesterol metabolism much if at all.
People may believe this due to the arterial calcification stuff. Arterial stiffening (which vitamin K reduces) can make arterial plaque and atherosclerosis worse, so vitamin K could indirectly help prevent plaque build-up by minimizing stiffening of the arteries.
However, the actual cholesterol molecules we talk about? The good and bad stuff? HDL, LDL, and vLDL are all unaffected—even triglycerides play no role here. Similarly, insulin sensitivity (which plays a major role in cardiovascular health) appears to be unaffected.
While very good for health, vitamin K isn’t a supplement that can act on many pathways at once. It can reduce arterial calcification but that’s about it, cholesterol is unaffected.
Vitamin K actually makes it into skin creams quite frequently alongside vitamin A.
It can be absorbed through the skin relatively easily, and there’s some evidence that it can help reduce abnormal reddening of the skin known as purpura. This, however, extended to the notion that it can help with any manner of discoloration.
When it comes to bruising, it doesn’t matter whether your cream has vitamin K in it or not but the bruises will still happen to the same severity—applying it after is quite unreliable and ineffective. It’s also claimed that vitamin K cream can help reduce symptoms of the skin pigmentation disorder vitiligo, but there’s no evidence of this.
Vitamin K has certain niche roles in a skin cream, but the idea that it can help with all discoloration is incorrect; just some help with purpura, and maybe some reddening.
Most studies that assess vitamin K intake over a long period of time also measure weight, mostly just because it’s easy to do and, well, everyone wants to lose weight.
Whenever weight is measured as a potential biomarker it’s consistently found to not be affected by vitamin K supplementation. Another study found that vitamin K supplementation had no effect on appetite, hunger, and voluntary food intake
Vitamin K plays no role in weight loss.
Supplementing vitamin K depends on both your own dietary intake of vitamin K and the specific form of vitamin K you choose to supplement.
To start with, and mostly get it out of the way, if you choose to supplement vitamin K as MK-4 for increasing bone mass then you will need to supplement 40 to 45 mg of it each day. This is the dose used by the studies on MK-4 and lower doses may not get the same benefits.
For all other purposes, any other form works at a lower dose. For MK-4 this seems to be somewhat arbitrarily set at 1.5 mg based on a few studies (which seems about comparable in benefits to 375 mcg MK-7).
Current effective doses are anything that can push you above the recommended daily intake (RDI) of vitamin K.
Naturally we need an upper limit, of course, and the best limit on intake we have right now is the particular vitamin K dependent proteins known as osteocalcin and Matrix GLA protein (MGP).
These two proteins mediate many of the benefits of vitamin K supplementation and it’s very much a “more is better” situation until they get saturated. When does this occur?
- 1,000 mcg (or 1 mg) of vitamin K1 (maximum osteocalcin activity)
- 320 to 500 mcg of vitamin K2 in the form of MK-7 (maximum MGP activity)
- 1,500 mcg (or 1.5 mg) of vitamin K2 in the form of MK-4.
There’s currently no known need to exceed either of those numbers, and you don’t necessarily need to supplement those exact numbers since you will get some vitamin K in your diet. A prudent approach may be to hit them half way—perhaps 500 mcg K1 or 250 mcg MK-7.
Vitamin K isn’t known to have any side-effects except when it comes to interacting with anti-clotting medication, particularly warfarin (brand name Coumadin) and other drugs that act in a similar manner.
This class of drugs works by preventing vitamin K from being able to clot blood, and are given to people who want to reduce clotting. A high vitamin K intake, of any form, can override and negate the drug from working.
If you want to take vitamin K, but you are on one of these drugs, then talk to your doctor first and see if an alternative can be prescribed that doesn’t negatively interact with vitamin K. Don’t, under any circumstances, use them at the same time.
Personally, I think most people should take vitamin K. It isn’t every day that we can make a claim that something is likely to reduce all cause mortality in all demographics.
The lack of side-effects to anybody not using warfarin or related pharmaceuticals is also a factor, so if you can just get a source of vitamin K that doesn’t cost a lot of money then supplementation will go a long way in your daily “stack.”
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Ultimately, vitamin K is a supplement that may not be as widespread as vitamin D but follows many parallels.
There was an RDI value established, later researched showed that while sufficient to prevent disease it’s not optimal, and bridging the gap through diet is quite difficult so supplements move in to fill the niche.
While more limited in scope than vitamin D, the benefits of vitamin K to the heart and bone health is quite notable while the ability of vitamin K to reduce arterial calcification and perhaps increase lifespan (via reducing all cause mortality) is very enticing.
It would be best to check to see if your multivitamin has, at least, 500 mcg K1 (555% of the RDA) or perhaps more.
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