Back
This micronutrient is tiny but mighty. Vitamin K is critical to creating proteins that our body needs to properly function including helping our heart and blood health.
Learning how to regulate vitamin K intake is especially important in healthcare because it dramatically influences blood thinner medication commonly used for many chronic conditions including heart disease and stroke.
Here's all about vitamin K: what it does, where to find it, and how much you need to support your health.
Vitamin K Benefits
1. Blood Clotting
Cuts and other wounds eventually stop bleeding because our bodies form a patch on the area that is often referred to as a ‘clot’.
Vitamin K is required to make proteins that allow blood to properly clot. While clotting too much can be a bad thing and cause catastrophes like strokes and heart attacks, clotting enough is also important in order to prevent dangerous bleeding.
Any cut or wound you’ve had heal has been, in part, because of vitamin K.
Because of this effect on blood clotting, vitamin K can also interfere with blood thinner medications (anticoagulants). This is why it’s so important for people on blood thinners to learn about how to manage their vitamin K intake when taking medications like warfarin.
As you might expect we need a balance. Our blood needs to effectively flow to supply our whole body with nutrients and oxygen. But we also need to be able to stop bleeding by clotting off injuries when they occur.
2. Heart Health
Because vitamin K helps make a protein that supports blood vessel health (matrix G1a proteins) it’s theorized that it also contributes to helping heart disease and helps to prevent blood vessel disease (atherosclerosis). However this has not yet been proven by well done studies.
3. Healthy Bones
Bones also benefit from vitamin K. It contributes to making proteins needed for bone health, in particular osteocalcin. Although some studies show conflicting results, it seems that getting enough of this micronutrient improves bone strength including bone mineral density and potentially helps to reduce the risk of broken bones (1).
What is Vitamin K
Vitamin K is a fat soluble vitamin, along with vitamins A, D and E. This means it can easily be absorbed into body tissues. There are two forms of vitamin K, called phylloquinone (K1) and menaquinone (K2).
Our bodies naturally produce a small amount of the menaquinone form. However, the amount we produce isn’t enough and we need to get the rest from what we eat.
Vitamin K Foods
A variety of foods contain adequate amounts of vitamin K. Green leafy vegetables are rich in phylloquinone (K1). Animal products and fermented foods contain menaquinones (K2).
Foods High in Vitamin K
Vitamin K Deficiency
Because it is so important for blood clotting, people without enough vitamin K can suffer from excessive bleeding.
| Vitamin K Minimum Recommended Daily Intake | |
| Adult Women | 90 mcg |
| Adult Men | 120 mcg |
Main Effects of Vitamin K Deficiency:
- Bleeding
- Bone Problems (osteopenia & osteoporosis)
With so many diverse nutrient rich foods, vitamin K deficiency is overall very rare. Like most vitamins, deficiencies can be seen in developing countries that don’t have readily accessible diverse nutrient dense foods.
Other populations at risk for a deficiency include infants and those with intestinal absorption disorders (ie: celiac disease, cystic fibrosis, inflammatory bowel disease, and people who have had bariatric surgery) (2).
Other Sources of Vitamin K
Vitamin K Shot
Because newborns have so little of this vitamin when they are first born, they are at risk for bleeding in a condition called ‘hemorrhagic disease of the newborn’. This is because their bodies make very little and breast milk contains lower than ideal levels for what babies usually need.
Newborns often get a vitamin K shot to help prevent them from suffering potentially life threatening bleeding.
Vitamin K Supplements
Most people can easily get enough of this micronutrient by eating a well balanced diet. Others prefer using dietary supplements to help ensure they are getting enough.
Most multivitamins contain enough vitamin K. There are of course individual supplements that exclusively contain the vitamin or combinations of a variety of micronutrients.
However, studies performed on adults in the United States found that most people were getting adequate intakes of this micronutrient. Both men and women were already consuming >120 mcg daily just from what they were eating. When supplements were added this number boosted >160 mcg of daily intake (3).
Therefore supplements can be most helpful in people with specific medical conditions, including those with problems absorbing nutrients.
Too Much Vitamin K
There actually haven’t been any dangerous effects found by taking in too much vitamin K from either food or supplements (4). A very important exception to this is people on anticoagulants (blood thinners) due to the potentially dangerous interactions vitamin K has with these medications.
As long as someone isn’t taking blood thinner medication, eating more of the vitamin doesn’t cause too much blood clotting or other dangerous conditions (2).
However, anyone who is taking blood thinning medications (anticoagulants), especially warfarin (coumadin) must carefully regulate how much vitamin K they consume to prevent dangerous side effects.
Warfarin & Vitamin K
Warfarin (aka coumadin) is a medication that helps to prevent blood clots. It does this by directly blocking the action of vitamin K, and therefore preventing the formation of many of the proteins that help blood to effectively form clots.
How effective the medicine is at preventing blood clots can be directly related to how much vitamin K someone eats. If large amounts of vitamin K are consumed, it may not be effective at preventing dangerous blood clots. Alternatively, if not enough vitamin K is consumed it can accentuate the effects of warfarin and cause dangerous bleeding.
Warfarin dosing can be adjusted to each individual based on how much vitamin rich foods they like to consume. It’s therefore less important how much of the vitamin someone on warfarin eats. Instead, what’s important is that people taking these medications eat the same amount of vitamin K consistently each day.
Because these effects can still be variable and influenced by many other factors (including many antibiotics), everyone taking warfarin must regularly get their blood tested to ensure that the levels are within a safe range.
Bleeding can be so dangerous and out of control in these populations that anyone taking blood thinner medications with any significant bleeding should seek immediate medical advice from their doctor or local emergency room.
To learn more about how to take warfarin safely read this article.
Bottom Line: Getting enough vitamin K is important for both our blood and bone health. It’s not something you need to worry about getting too much of. People who are on blood thinners like warfarin need to be very careful about consistently consistent amounts of vitamin K each day.