Vitamin K


What is vitamin K?

Vitamin K is a fat-soluble vitamin that is needed to build and maintain strong bones. It is necessary for osteoblasts (bone building cells) to activate osteocalcin, a protein that binds calcium to bones. Vitamin K may also block the production of osteoclasts, the cells responsible for breaking down bone. It is also involved in blood clotting.

What is the recommended daily intake for vitamin K?

The adequate intake (AI) for vitamin K is 120 mcg (micrograms) per day for men and 90 mcg per day for women.

What are typical intakes for vitamin K?

Among U.S. adults, the average reported intakes of vitamin K are below the recommended intakes. However, Vitamin K deficiency is very rare and occurs when there is an inability to absorb the vitamin in the intestine. Vitamin K deficiency can also occur after prolonged treatment with antibiotics which disturbs the balance between good and bad bacteria in the intestines. Individuals with vitamin K deficiency usually have an increased tendency to bruise or bleed.

What foods contain vitamin K?Vitamin K

Most healthy individuals can easily consume the recommended amount of Vitamin K by eating a nutrient-rich diet. Foods with generous amounts of vitamin K include certain dark green leafy vegetables (such as kale, collard greens, spinach, mustard greens, turnip greens and brussel sprouts) and certain vegetable oils (soybean, canola, cottonseed, and olive). Kale is one of the richest sources of vitamin K. One cup of cooked kale contains more than 1000 mcg of vitamin K. One cup of cooked broccoli contains about 300 mcg of Vitamin K. Click here for more information about vitamin K provided by USDA National Agricultural Library

How does vitamin K affect bone health?

Some population studies report that low vitamin K intakes appear to be associated with an increased risk of hip fractures among older men and women. However, it is not certain whether the increase in fracture rate is entirely due to low vitamin K intake. In some studies, higher dietary vitamin K intakes were also associated with higher consumption of green leafy vegetables. There may be other characteristics of a diet higher in fruits and vegetables that could be responsible for lower fracture risk. Perhaps it is the other vitamins and/or minerals present in fruits and vegetables or the effect of fruits and vegetables on acid-base balance that works to lower fracture risk. Some scientists believe that higher intake of fruits and vegetables containing vitamin K is simply suggestive of an overall healthy diet. In that case, it could possibly be poor overall nutrition rather than vitamin K alone that increases the risk of hip fracture. Future research is needed to clearly understand the relationship of vitamin K to bone health.

What should I do to make sure that I get adequate vitamin K?

Getting adequate vitamin K in your diet may help promote strong bones. The best way to get the vitamin K you need is to eat a nutrient-rich diet that contains a variety of foods with special emphasis on eating green leafy vegetables. For strong bones and a healthy heart, it is wise to use vegetable oils (that are high in vitamin K), in moderation, as part of your fat intake.

Are vitamin K supplements recommended for strong bones?

There is not enough data to recommend vitamin K supplements for osteoporosis prevention or treatment.

Are there any special considerations about vitamin K?

It is important for people taking blood-thinning medications (such as warfarin, brand name: Coumadin) to know that food containing vitamin K or vitamin K supplements may reduce the effectiveness of their medication. If you take blood-thinning medication, your healthcare provider may tell you to avoid vitamin K from food and/or supplements. It is important to follow the advice of your healthcare provider. Do not stop or change the way you take your medications without your healthcare provider’s direction to do so. It is important to be aware that chronic use of blood thinning medications may increase the risk for bone loss. Speak to your healthcare provider about how to treat your medical condition and promote strong bones, too.

Click the link below to read our factsheet on Vitamin K and bone health.