Vitamin K is a nutrient that the body needs to stay healthy. It’s important for blood clotting (which means it helps wounds to heal properly) and healthy bones and also has other functions in the body.
Vitamin K deficiency
Vitamin K deficiency is very rare. Most people in the United States get enough vitamin K from the foods they eat. Also, bacteria in the colon make some vitamin K that the body can absorb. However, certain groups of people may have trouble getting enough vitamin K:
- Newborns who don’t receive an injection of vitamin K at birth
- People with conditions (such as cystic fibrosis, celiac disease, ulcerative colitis, and short bowel syndrome) that decrease the amount of vitamin K their body absorbs
- People who have had bariatric (weight loss) surgery
What foods provide vitamin K?
Vitamin K is found naturally in many foods. You can get recommended amounts of vitamin K by eating a variety of foods, including the following:
- Green leafy vegetables, such as spinach, kale, broccoli, and lettuce
- Vegetable oils
- Some fruits, such as blueberries and figs
- Meat, cheese, eggs, and soybeans
How much vitamin K do I need?
The amount of vitamin K you need depends on your age and sex. Average daily recommended amounts are listed below in micrograms (mcg).
|Life Stage||Recommended Amount|
|Birth to 6 months||2.0 mcg|
|7-12 months||2.5 mcg|
|1-3 years||30 mcg|
|4-8 years||55 mcg|
|9-13 years||60 mcg|
|14-18 years||75 mcg|
|Adult men 19 years and older||120 mcg|
|Adult women 19 years and older||90 mcg|
|Pregnant or breastfeeding teens||75 mcg|
|Pregnant or breastfeeding women||90 mcg|
Which vitamin K is the best and where do you find it?
The three types of vitamin K are the following:
- Vitamin K1, or phylloquinone, is found naturally in plants, especially green vegetables; K1 goes directly to your liver and helps you maintain healthy blood clotting
- Vitamin K2, also called menaquinone, is made by the bacteria that line your gastrointestinal tract; K2 goes straight to your blood vessel walls, bones, and tissues other than your liver
- Vitamin K3, or menadione, is a synthetic form I do not recommend; it’s important to note that toxicity has occurred in infants injected with this synthetic vitamin K3
The vitamin K2 is best for supplementation because is natural and not toxic, at even 500 times the RDA. Vitamin K2, which is made in your body and also produced by fermented foods, is a superior form of vitamin K1.
Increasing your K2 by consuming more fermented foods is the most desirable way to increase your levels. Vitamin K2 is mainly found in certain animal foods and fermented foods, which most people don’t eat much of. Rich animal sources include high-fat dairy products from grass-fed cows, liver and other organs, as well as egg yolks.
The food highest in natural K2 is natto, which is a form of fermented soybeans consumed in Asia. Sauerkraut and miso contain K2 too.
Can vitamin K be harmful?
Vitamin K has not been shown to cause any harm. However, it can interact with some medications, particularly with blood thinner warfarin and it can cause bleeding or blod clots. Before you take vitamin K supplements consult your doctor.