Think back to the last time you were bleeding–papercuts, scraped knees, sliced fingers from overzealous meal prepping. Do you remember how long it took for the wound to stop bleeding? Maybe it was small enough to finish within a minute. Or maybe you covered it with a bandage and didn’t check until hours after it stopped. Either way, unless you have a specific medical condition, the wound stopped bleeding thanks to blood clotting (or coagulation).
Without coagulation, you would still be bleeding now. There’s an agent behind the plug that you need to thank for saving you rolls of expensive gauze and new carpeting. An agent that you can find in your diet but may not be getting enough of.
Meet vitamin K, the essential dietary vitamin that stops you from bleeding out and much, much more.
Vital Signs: Vitamin Basics
Everyone knows what vitamins are. But if someone were to ask you to define a vitamin, what would you say? Simple question, complex concept. Unless you’re a dietitian or other medical professional, you may struggle to give a confident answer. And with the endless discordant sound bites about vitamin deficiencies, vitamin supplements, and vitamin-rich foods we should (or shouldn’t) be eating, it makes this question even more challenging to answer.
What’s a Vitamin?
Even though James Lind1 first discovered lemon juice could treat scurvy in sailors in the mid-eighteenth century, it would be nearly a hundred years before anyone would know why it worked. It was merely a happy accident that he tested vitamin C-rich citrus fruits to those with a vitamin C deficiency. His less successful remedies? Half a pint of seawater daily, a pungent paste made of horseradish and garlic taken thrice daily, and six spoonfuls of vinegar throughout the day.
In the nineteenth century, physiologists identified four nutrient sources from our foods. In addition to the classic macronutrient trio of carbohydrates, proteins, and fats, they identified water as a comparable component of the diet. But it wasn’t until more research was being done into nutritional deficiencies that cause diseases, such as beriberi and rickets, that the physiologists came to identify the major micronutrients we also require.2
In 1913, Polish biochemist Casimir Funk observed that the hulk of unprocessed rice contained something to protect chickens from beriberi. He published his findings regarding the discovery of this “vital amine” with the proposed term “vitamine” to describe essential accessory factors of our diets. It wasn’t until 1926 that this “vitamine” was able to be isolated, named “thiamine,” and renamed vitamin B1 a decade later.2
Fast Facts: Vitamin Edition
In essence, a vitamin is an organic compound (meaning it contains carbon) that is separate from the macronutrients: fats, proteins, and carbohydrates. However, the current definition of a vitamin has several parameters. In addition to being an organic compound, a vitamin is a natural component of foods.
Vitamins are generally present in our foods in very small amounts. These small amounts are essential for our normal physiological function, such as growth and development.
When a vitamin is underutilized or completely absent, it can cause a specific deficiency syndrome. Conversely, vitamins prevent these deficiencies. Lastly, vitamins are not synthesized by their hosts in adequate amounts to meet normal physiological needs, hence the need to obtain them from our foods.2
Vitamins belong to two categories: fat-soluble or water-soluble. The fat-soluble vitamins are those stored in the fatty tissues and the liver. They are much easier for the body to store than water-soluble vitamins, so they’re able to hang out in reserves anywhere from a few days up to a few months. We absorb fat-soluble vitamins through the intestinal tract with the help of fats themselves. The fat-soluble vitamins include A, D, E, and our vitamin VIP, K.
Water-soluble vitamins leave the body pretty quickly. Because we cannot store them the same way we can store our fat-soluble vitamins, they pass through the liquids in our bodies. In other words, we pee them out, so we’ll need to replenish them more often than the fat-soluble vitamins. If you check the missing letters from our fat-soluble alphabet, you’ll figure out that vitamins B and C are water-soluble.
Vitamins vs. Minerals
Now that we’re on the same page with what qualities constitute a vitamin, we can talk about all the different vitamins. One problem we may run into is the inadvertent inclusion of a completely different class of nutrients that are often lumped together with vitamins: minerals.
You’ve no doubt heard it before: “vitamins and minerals.” They’re often inseparable in discussions. But when it comes to nutrition, they couldn’t be more distinct. Recall that vitamins are organic compounds. Minerals? Inorganic substances. Vitamins are obtained through plants or animals synthesizing them. For instance, humans can make vitamin A from the beta-carotene we get when we eat carrots.
Minerals are easier to come by; you can literally find them under a rock. Or in one, rather, in addition to the soil beneath it. The delicate nature of vitamins makes them sensitive to destruction through certain cooking techniques. Minerals on the other hand are completely unfazed by not only high heat but also chemical reactions.
While both vitamins and minerals are required for proper body function, you don’t need all minerals the same way you need all vitamins. Remember that if a vitamin is absent or unsatisfactory, you will suffer from a deficiency disease (scurvy, anyone?). You don’t need to consume every mineral to maintain healthy functioning. There are 16 essential minerals listed below. Try to think of as many as possible before you read them.
There are 14 essential vitamins our bodies need, each with its own sources, functions, and deficiency symptoms when lacking.
- Vitamin A
- Vitamins B1-3, 5-9, 12
- Vitamin C
- Vitamin D
- Vitamin E
- Vitamin K
Vitamin K may last, but it is certainly not least.
Vitamin K Essentials
Now that we have a better understanding of what vitamins are and how they work, we can zoom in on our celebrity compound, vitamin K.
Vitamin K was discovered after Danish scientist, Henrik Dam, went searching for the cause of hemorrhaging in chicks being fed low-fat diets in 1929. Several trials and one misdiagnosis of scurvy later, he found that a new fat-soluble factor present in plant and animal tissues was the missing vitamin needed to coagulate the blood. He fittingly (perhaps even unimaginatively) named this new discovery “Koagulations vitamin,” hence the K.3
Vitamin K can be broken down into two different types with very long and pronunciation-flexible titles: Phylloquinone and menaquinone. But if you’re not trying to impress a scientist, you can just refer to them as vitamin K1 and K2, respectively.
Vitamin K may not ring a bell the way other vitamins do. You could no doubt name rich sources of vitamin E, vitamin D, and vitamin A, and if you’re an overachiever, you could probably explain why we need them. But vitamin K gets overshadowed, and with its list of benefits, it’s hard to imagine why.
Vitamin K: Endless Cycle
Process this process: you have your very own vitamin K cycle taking place in your body right now.
In this metabolic process, your vitamin K undergoes some chemical changes, which facilitate the functions of certain proteins. Vitamin K is a cofactor for the enzymes contributing carboxyglutamic acid to proteins until they become a special class called Gla proteins.
Even if these proteins don’t sound familiar, your body knows them well—they’re involved in both blood clotting and bone metabolism, which we’ll discuss more in detail later.
For now, read on for where to find K1 and K2, what supplementing with the vitamin can do for our bodies, and what the future of the vitamin holds for our cognitive performance.
Where to Get Vitamin K
Thanks to Henrik, you won’t have to suffer low-fat diets and hemorrhaging to figure out what food sources contain vitamin K.
Phylloquinone (K1) is the type of vitamin K you’ve been told to eat your entire life. It’s one of many vitamins and minerals packed into the bundles of joy you visit in the produce aisle every week:
- Dark leafy greens: kale, mustard greens, spinach
- Green vegetables: broccoli, cabbage, Brussels sprouts
- Fruits: prunes, kiwi, avocado, blackberries
- Nuts and legumes: walnuts, chickpeas, pistachios, raw sugar peas, kidney beans
K1 is a fat-soluble vitamin, which as we discussed earlier, means it dissolves in fats and should be paired with fatty foods to be properly absorbed. It also means you have an excuse not to skimp on the oil-based dressing or extra sprinkle of nuts.
Menaquinone (K2) is the type of vitamin K you’ve been told to regulate—or even eliminate. That’s because K2 is a bacteria-based vitamin only present in fermented foods and fatty animal products, such as egg yolks and cheese.4 Here’s your excuse to let the waiter continue grating parmesan on top of your pasta.
Preserving Vitamin K Content
Earlier, we discussed the delicate nature of vitamins, which means excessive heat can damage them. Food preparations such as roasting, steaming, and microwaving can all affect the nutrient profile of your food.5 Each method has its merits and shortcomings.
Take vitamin K-rich broccoli, for example. Most of us aren’t interested in eating it raw. For good reason: even a simple steaming of this cruciferous veggie leads to an increase in its total amount of glucosinolates, which are sulfur-containing sugars with a powerful flavor,6 and even more powerful health benefits, such as assisting in the protection against cardiovascular disease and cancer progression.7
But if you choose to microwave broccoli instead, you may damage its vitamin C content.8 On the upside? Its vitamin K supply will remain largely intact, as vitamin K appears to stand up well to the pressure of cooking via gamma-irradiation.9
In greens such as spinach, broccoli, and lettuce, the bioavailability of phylloquinone (K1) appears to be roughly the same when eaten raw or cooked.
Supplementing with vitamin K1 in tandem with consuming the greens, however, appeared to increase the bioavailability of the nutrient.10
Vitamin K Deficiency
Whether food is cooked or raw, the problem is that many people don’t get the right amount of vitamin K through food alone. Children’s dietary vitamin K1 intake was significantly higher in 1950 than it is today because kids aren’t eating as many food sources containing phylloquinone.11 Even American adults are consuming less vitamin K1and K2 than the dietary reference intakes set by the US Food and Drug Administration.12
These daily targets become even more difficult to hit with specialized diets, food allergies, and processed foods, which is why vitamin K supplementation is an efficient way to ensure you have an adequate intake of vitamin K1 and K2.
Serious vitamin K deficiency has some not-so-subtle symptoms associated with a lack of clotting factors: bruising easily, bleeding excessively, blood clotting underneath your fingernails, and very dark stool that contains blood.
To test for a vitamin K deficiency, a healthcare professional will usually perform a blood test measuring how long it takes for your blood to clot, otherwise known as the prothrombin test (PT). After taking a small blood sample with a needle, the professional will add chemicals to (hopefully) observe quick clotting. It usually takes about 11 to 13.5 seconds for the blood to clot. If you’re vitamin K deficient, yours will likely take longer.
Outside Influencers on Vitamin K
Let’s say you’re getting a proper amount of vitamin K through your diet alone. You could still be at risk of vitamin K deficiency if you have malabsorption syndrome.
Malabsorption syndrome is an umbrella term for numerous disorders in which the small intestine is unable to absorb adequate levels of nutrients and fluids.13 Often, it’s the micronutrients that go amiss: vitamins and minerals.
Unfortunately, there are several factors that can lead to malabsorption syndrome. Diseases such as celiac, Crohn’s, cystic fibrosis, and chronic pancreatitis are some common culprits. Others include long-term use of antibiotics, surgery or trauma-induced damage, congenital defects, radiation therapy, and the inability to produce certain digestive enzymes.13
If you’re a newborn, first of all, how are you reading this, and second of all, you have an even greater chance of developing a vitamin K deficiency. Newborn babies’ bodies are not set up for vitamin K success because they’re unable to produce any vitamin K2 on their own in their initial days of life, and even when they do, the liver doesn’t utilize the vitamin efficiently. Outside sources? Tough luck—vitamin K isn’t exactly known for its smooth transfer from the mother’s placenta. Even breast milk is no help. The solution is usually a small shot of vitamin K administered at birth.14
What Has Vitamin K Done for You Lately?
While obtaining your daily recommended intake of vitamin K is necessary for proper coagulation and staving off hemorrhagic disease, vitamin K is also important for bone and cardiovascular health, with particular benefits noted when taken in higher doses.
The key here is higher doses. You could always eat half a pound of Natto, the menaquinone-rich fermented soybean dish of Japan whose taste is lovingly described as bitter, pungent, and above all, acquired. But until you’ve acquired that taste, you’re welcome to vitamin K supplementation over obtaining it through food.
Regulated Bone Mineral
You have a bone to pick with vitamin K2. All of them, actually, because vitamin K plays a large role in supporting bone health through its modification of the osteocalcin protein involved in bone formation.
Without K2, osteocalcin is unable to bind with calcium, the main mineral found in your teeth and bones.15 Thus, low dietary intake of vitamin K is associated with lower bone mineral density and accelerated bone loss (BMD). Vitamin K is especially effective at protecting two areas from low BMD: the femoral neck and the lumbar spine.15,16
Reduced Risk of Osteoporosis
Picture your bones this way. They’re porous, brittle, and screaming “osteoporosis” at you with every creaking movement.
Osteoporosis greatly increases the risk of a fracture, no matter how small the movement is. Something as minor as a cough could put enough strain on osteoporotic bones to cause them to crack under pressure.
Luckily, an analysis of 80,982 subjects found a significant inverse association between vitamin K status and fracture risk. Subjects who reported the highest dietary intake of vitamin K had a 22% reduction in the risk of bone fractures.17 What’s more, when vitamin K was added to a mineral supplement administered for bone loss protection, it led to complete femoral neck protection for the first year with a 35% reduction in bone loss rate in the subsequent three years.16
Reduced Risk of Heart Disease
Recall that vitamin K2 regulates calcium deposition through vitamin K-dependent proteins, one of which is the calcium-binding osteocalcin. Another protein, the matrix Gla protein (MGP), also regulates calcium deposition by inhibiting the calcification of arteries and cartilage,18 known as vascular calcification.19
Think of this vitamin K cycle as a scavenger hunt for calcium ions in the blood.
When proteins express glutamate, it’s like a clue for vitamin K to target these proteins in order to collect the calcium ions floating around in the blood.
But this scavenger hunt carries a hefty prize as calcification around the heart is a huge risk factor for the most-wanted killer in the United States: heart disease.
A 2009 study found that higher menaquinone intake was closely associated with reduced coronary calcification,20 and another 2009 study further observed that higher menaquinone intake reduced the risk of coronary heart disease.21
Try saying this section title five times fast. Sphingolipids are major components of all mammalian cell membranes; they’re present in high concentrations in cells of the peripheral and central nervous system.22 These lipids play an important role in major cellular events, including: proliferation, cell to cell interaction, transformation, and differentiation.23
Much like the protein regulation of bone and heart health, vitamin K modulates sphingolipid metabolism through two key proteins: Gas6 and Protein S. Gas6 is primarily involved in cell growth and cell survival, while Protein S is involved with neuronal protection.23
Though research on vitamin K and its effects on cognition is in its infancy, current findings point to vitamin K as a crucial nutrient for the central and peripheral nervous systems,23.
Vitamin D: How is it Related?
Maybe you haven’t started addressing a vitamin K deficiency because you’re focused on a vitamin D deficiency.
Vitamin D is another fat-soluble vitamin that plays a role in maintaining bone health, supporting the immune and nervous systems, regulating insulin levels, and supporting lung and cardiovascular functions.24 We produce the vitamin most efficiently in the skin through regulated exposure to UVB rays from the sun. Secondarily, we get it through eggs, mushrooms, and fatty fish.
Like vitamin K, however, many people simply aren’t getting enough of this vitamin through their diet and sun exposure alone.25
An estimated 36% of healthy young adults in America are getting inadequate levels of vitamin D.
The numbers are even higher in places with limited sunlight. Think Denmark26 and Sweden during the winter. This percentage has increased significantly since the 1990s, to the point that several researchers describe the deficiency as an epidemic.27,28,25,24
Vitamin D deficiency symptoms are fitting for a lack of sunshine: increased risk of certain illnesses,29 lower back pain,30 depression,31 bone loss,32 and fatigue.33 To prevent these dreary symptoms, many people supplement with vitamin D.
Directing Calcium Traffic
When you’re getting enough of it, vitamin D enhances calcium absorption from the foods you eat to use for bone health.34 But this organic compound is no miracle worker. If the calcium levels in your blood are still low, there’s only so much it can do. Vitamin D is forced to get crafty with other sources of calcium in your body if you don’t consume enough through your foods. The best source? The very bones it can help you build.35
When vitamin D takes calcium from your bones’ tempting treasure trove, it keeps your blood levels in check. But it doesn’t have much of a say in what happens to the calcium in your bloodstream. Can you guess who does?
Vitamin K activates that special protein, osteocalcin, which you may recall stimulates the gradual gathering of calcium in your teeth and bones.15 The other potent protein it regulates, the matrix Gla protein (MGP), also directs this calcium traffic by inhibiting the calcification of your arteries and cartilage.18
If you are supplementing with vitamin D or plan to, adding vitamin K to the mix may be important for more than just getting the most out of the calcium in your blood; it may be good for getting all that excess calcium out of your blood.
Recall that vitamin D’s role is to introduce calcium into your bloodstream. If you’re assisting this process with a vitamin D supplement, your vitamin D levels could rise above what your blood can handle. As for the blood’s calcium content? That could spike as well, leading to a condition called hypercalcemia.36
Hypercalcemia denotes extremely high levels of calcium and phosphorous in the blood, which means the combination (calcium phosphate) starts squatting in your blood vessels. This accumulation is called blood vessel calcification, or BVC.37
Blood vessel calcification is particularly undesirable because it can contribute to heart disease.38 BVC has also been associated with vitamin K deficiency.39 That’s the bad news. The good news is high dose vitamin K supplements have been able to prevent BVC in animal studies. Better yet?
Human studies on the effects of vitamin K on the rates of coronary artery calcification have yielded promising results in elderly patients.
Those taking vitamin K1 experienced 6% less coronary artery calcification progression than those who did not.40 But vitamin K wasn’t alone in its quest—it was administered alongside recommended amounts of vitamin D and calcium, lending further evidence into the important relationship between these bone-strengthening compounds.40
A 2002 study about the combined effects of vitamin K and vitamin D found a significant increase in bone mineral density in postmenopausal women.41 The participants in the study all had osteoporosis or osteopenia. Osteopenia indicates reduced protein and mineral content in the bones but not to the degree of osteoporosis. After two years of continuous supplementation of both vitamins, subjects experienced nearly a 5% increase in bone mineral density.41
Supplementing with Vitamin K1 and K2
When taking vitamin K dietary supplements, make sure you’re getting both vitamin K1 and K2. To feel 100%, you should take at least 50mcg of K1 and no more than 1,000mcg. For K2, you’ll need at least 100mcg.
Because vitamin K is fat-soluble, it should be taken at mealtimes containing a fat source. These benefits can accrue over time. So setting up a consistent, daily-use routine encourages better results. Every morning, when you sit down for breakfast (or lunch), try adding a vitamin K supplement to your routine. Plus, it’s a nice excuse to eat some healthy fats! Maybe try an avocado, cheese, nuts, or, if you’re feeling crazy—some dark chocolate.
Keep in mind that vitamin K is a coagulant and should not be combined with antihemorrhagic medications such as Coumadin unless instructed by your healthcare provider.
Vitamin K Leads the Way
The Institute of Medicine lists vitamin K alongside other essential micronutrients, such as zinc, copper, iron, and chromium, which we now know are considered to be minerals. But vitamin K’s benefits go up with the dosage.
Whether your blood is clotting normally or not, let’s quickly review how you can benefit from higher vitamin K intake.
Higher amounts of vitamin K can:
- Regulate bone minerals and bone metabolism
- Reduce risk of osteoporosis
- Reduce risk of bone fracture
- Inhibit vascular calcification
- Reduce risk of heart disease
- Synthesize sphingolipids involved in cognitive functions
Next time you find yourself bleeding, save the swear words and try saying “thank you” to vitamin K.