Vitamin K image Vitamin K is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body in the liver and fatty tissues. Unlike the other fat-soluble vitamins, the body actually stores very little vitamin K, making regular dietary intake important. Bacteria in the large intestines help out by making a range of vitamin K forms called menaquinones. Vitamin K is also produced by plants (phylloquinone) and is primarily found in green vegetables (collards, spinach, salad green, broccoli), Brussels sprouts, cabbage, and plant oils. The manmade vitamin K found in supplements is called menadione.

Functions

Vitamin K’s functions include:

  • Playing an essential role in the blood-clotting process by making the proteins that stop bleeding
  • Helping your body make other proteins essential for blood, bones, and kidneys

Recommended Intake:

Age Group
(in years) 		Adequate Intake (AI)
(in micrograms)
FemalesMales
1-33030
4-85555
9-136060
14-187575
14-18 Pregnancyn/a
14-18 Lactation
19+90120
19+ Pregnancyn/a
19+ Lactation

Vitamin K Deficiency

If you don’t get enough vitamin K, your blood will not clot normally. Among healthy people, a deficiency is rare. Symptoms of vitamin K deficiency include:

  • Easy bruising and bleeding (nosebleeds, bleeding gums, blood in the urine, blood in the stool, or extremely heavy menstrual bleeding)
  • Bleeding in the skull (intracranial hemorrhage) in infants

Vitamin K Toxicity

As a fat-soluble vitamin, vitamin K is stored in the body and not excreted in the urine like most water-soluble vitamins. Though no symptoms have been observed among people consuming excess amounts, moderation is still recommended. People taking blood-thinning drugs, or anticoagulants, may need to limit their intake of vitamin K-rich foods because too much vitamin K can make those drugs less effective in thinning the blood. In some infants given injection, the synthetic forms of vitamin K (menadiones), have caused liver toxicity, jaundice , and rupture of the blood cells. No tolerable upper intake level (UL), that is the highest amount a healthy individual can consume without endangering their health, has been established for vitamin K.

Major Food Sources

FoodServing Size Vitamin K Content
(micrograms)
Spinach (fresh/frozen, boiled)½ cup360
Brussels sprouts(fresh/frozen, boiled)5 sprouts289
Broccoli(fresh/frozen, boiled)½ cup113
Cabbage (fresh, boiled)2/3 cup98
Asparagus(fresh/frozen, boiled)7 spears80
Soybean oil1 Tbsp27
Canola oil1 Tbsp21
Kiwi fruit1 medium20
Avocado1 small14
Olive oil1 Tbsp4

Health Implications

Populations at Risk for Vitamin K Deficiency

The following groups of people may be at risk for a vitamin K deficiency and may require a supplement:

People taking anticoagulant, or blood-thinning, drugs –It is generally recommended that people taking these drugs try to consume the adequate intake for vitamin K (90-120 micrograms) from food sources, but not more. Supplementing vitamin K can cause drug interactions in people taking anticoagulant or blood-thinning drugs. Vitamin K deficiency is uncommon in healthy adults.

If you are taking an anticoagulant, talk to your doctor about your vitamin K intake before changing your eating habits. Drastic changes in the amount of vitamin K you eat can affect how these drugs work.

People taking antibiotics –In addition to killing harmful bacteria, antibiotics also destroy the healthful bacteria that live in the intestines and produce vitamin K.

People with liver disorders –The liver plays an important role in metabolism and storage of vitamin K. Persons with severe liver disease may require vitamin K supplementation to avoid complications of bleeding or bruising.

Exclusively breastfed newborn babies who do not receive a vitamin K injection –These babies may be deficient because:

  1. Human milk can be low in vitamin K
  2. Newborns do not yet have the bacteria that will make vitamin K in their intestines
  3. Body cycles that help to recycle vitamin K are not yet fully functional

For these reasons, and because a deficiency of this vitamin can be life-threatening, the American Academy of Pediatrics recommends that all newborns receive an injection of phylloquinone, the plant-based vitamin K. This is the standard of care in many hospitals.

Tips For Increasing Your Vitamin K Intake:

  • Slice an avocado. Add a little balsamic vinegar and pepper, and scoop out for a snack. Or, mash the avocado and mix with chopped tomatoes and red onions for a refreshing salsa.
  • Pack a kiwi and spoon in your lunch for an afternoon snack. The insides of the kiwi can be scooped out and eaten from this natural and easy container.
  • Steam ½ cup broccoli or Brussels sprouts, add lemon juice (1 Tbsp), pre-chopped garlic (1 tsp), and Dijon mustard (1 Tbsp). Or add broccoli to your favorite lasagna or hot dish.
  • Mix 2 (10-ounce) packages of frozen chopped spinach, thawed, well drained, 1 8-ounce package of softened low-fat cream cheese, ¼ cup milk, and 1 teaspoon lemon pepper until well-blended. Spoon into a 1-quart casserole dish and sprinkle with 1/3 cup crushed crackers or seasoned croutons. Bake at 350 degrees until thoroughly heated (about 25-30 min.).