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Publication #FCS8666

Facts about Vitamin K1

R. Elaine Turner2

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Why do we need vitamin K?

Vitamin K is one of the fat-soluble vitamins. It helps the body make proteins that are needed for normal blood clotting. Vitamin K also is needed for making important bone proteins.

What happens if we don't get enough vitamin K?

Not getting enough vitamin K can cause serious problems with blood clotting. Without vitamin K, blood takes a long time to clot. This can cause excessive blood loss and increased risk of death from injuries.

Anticoagulant medications such as warfarin (Coumadin)interfere with normal use of vitamin K in the body. Eating very large or very small amounts of vitamin K can change how these drugs work. So it's best to limit your intake of foods such as spinach and turnip greens, which are very high in vitamin K. If you take an anticoagulant, keep your vitamin K intake consistent from day to day.

People who take anticoagulants should check with their doctor before taking vitamin E supplements, or herbs such as ginkgo and garlic. High doses of vitamin E can interfere with the action of vitamin K in the body.

How much vitamin K do we need?

The following table lists recommended daily intakes of vitamin K:

Table 1. 

Life Stage

Vitamin K

(µg/day)

Men, ages 19+

120

Women, ages 19+

90

Pregnancy

90

Breastfeeding

90

µg = micrograms

How can we get enough vitamin K?

Vitamin K is found mostly in vegetables, especially green vegetables. Collards, spinach, broccoli, Brussels sprouts, and cabbage contain vitamin K. Some fruits, such as kiwi, blackberries, and blueberries are also good sources.

Here are some foods and the amount of vitamin K they contain:

Table 2. 

Food

Vitamin K

(µg per serving)

Turnip greens, cooked, ½ cup

425

Spinach, raw, 1 cup

145

Broccoli, cooked, ½ cup

110

Cabbage, cooked, ½ cup

37

Kiwi fruit, 1 medium

30

Blackberries, 1 cup

30

Okra, cooked, ½ cup

30

Blueberries, 1 cup

30

Red grapes, 1 cup

25

Green beans, cooked, ½ cup

10

µg = micrograms

We also get some vitamin K from the bacteria that normally live in our large intestines. These bacteria make vitamin K and we are able to absorb some of it.

Newborns have very little vitamin K in their bodies. They usually receive a shot of vitamin K soon after birth. This shot of vitamin K allows normal blood clotting to occur during the first weeks of life.

What about supplements?

Most people get plenty of vitamin K in their diet, so supplements usually are not needed. Multivitamin supplements are available with or without vitamin K. If you take an anticoagulant, avoid supplements that contain vitamin K.

Research has not yet found problems from consuming too much vitamin K from food or supplements, except for people who take anticoagulant medications.

Where can I get more information?

The Family and Consumer Sciences (FCS) agent at your county Extension office may have more written information and nutrition classes for you to attend. Also, a registered dietitian (RD) can provide reliable information to you.

Reliable nutrition information may be found on the Internet at the following sites:

Footnotes

1.

This document is FCS8666, one of a series of the Department of Family, Youth and Community Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: June 2001. Revised: April 2006. Please visit the EDIS Web site at http://edis.ifas.ufl.edu

2.

R. Elaine Turner, PhD, RD, associate professor, Food Science and Human Nutrition Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.