Vitamin K

What is vitamin K ?

Vitamin K is a fat-soluble vitamin that is needed to build and maintain strong bones. Vitamin K is necessary for osteoblasts (bone building cells) to activate osteocalcin, a protein that binds calcium to bones. It may also inhibit the production of osteoblasts, the cells responsible for breaking down bone. Vitamin K is also involved in blood clotting. It is easy for most healthy individuals to consume the recommended amount of Vitamin K by eating a nutrient-rich diet.

What is the recommended daily intake for vitamin K?

The adequate intake (AI) for vitamin K is 120 ug per day for men and 90 ug 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. For example, vitamin K deficiency can occur after prolonged treatment with antibiotics when the bacteria in the intestinal tract is disturbed. Individuals with vitamin K deficiency usually have an increased tendency to bruise or bleed.

What foods contain vitamin K?

Dietary sources 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). It's easy to get enough vitamin K from green vegetables. Kale is one of the richest sources of vitamin K. One cup of cooked kale contains more than 1000 ug of vitamin K. One cup of cooked broccoli contains about 300 ug of Vitamin K. Click here for more information about the vitamin K content of selected foods listed according to nutrient content or listed alphabetically.

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 enough vitamin K?

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 to know that vitamin K supplements or food containing vitamin K may reduce the effectiveness of their medication. If you take blood-thinning medication, your healthcare provider may tell you to avoid vitamin K from dietary and/or supplemental sources. The long-term use of high doses of blood-thinning medication may be a risk factor for osteoporosis. It is important to speak to your healthcare provider about how to treat your medical condition and promote strong bones, too. Always follow the advice of your doctor or healthcare provider.