Functions | Recommended Intake: | Vitamin K Deficiency | Vitamin K Toxicity | Major Food Sources | Health Implications | Tips For Increasing Your Vitamin K Intake

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. This makes regular dietary intake important. Bacteria in the large intestines help 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 man-made 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 do not get enough vitamin K, your blood will not clot normally. Among healthy people, a deficiency is rare. Symptoms of vitamin K deficiency include:

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. While allergic reactions could happen, no symptoms have been observed among people consuming excess amounts of the natural-form of vitamin K. There have been some problems associated with the man-made form of the vitamin (menadione), though. Some infants who were given injections of menadione had liver toxicity, jaundice, and rupture of the blood cells. No tolerable upper intake level (UL)—that is, the highest amount healthy people can consume without endangering their health—has been established for vitamin K. But, to be safe, you should follow the intake guidelines based on your age and gender.

Major Food Sources

FoodServing Size Vitamin K Content
(micrograms)
Spinach, raw1 cup145
Mayonnaise1 tbsp3.7
Broccoli, cooked1 cup (chopped) 220
Kale, raw1 cup (chopped) 547
Leaf lettuce (green), raw 1 cup (shredded)62.5
Soybean oil1 tbsp25
Canola oil1 tbsp16.6
Swiss chard, raw1 cup 299
Watercress, raw1 cup (chopped) 85
Olive oil1 tbsp8.1

Health Implications

If you take a blood-thinning drug (anticoagulant), try to consume the recommended intake of vitamin K (90 mcg). Avoid exceeding this. Taking a vitamin K supplement can cause drug interactions. Talk to your doctor about your how much vitamin K is safe for you.

In addition to killing harmful bacteria, antibiotics also destroy the healthful bacteria that live in the intestines and produce vitamin K. You may need to add more foods rich in vitamin K to your diet. Ask your doctor.

The liver plays an important role in metabolism and storage of vitamin K. If you have severe liver disease, you may need to take a vitamin K supplement to avoid complications (eg, bleeding or bruising).

Because vitamin K deficiency can be life-threatening in newborns, the American Academy of Pediatrics recommends that all newborns receive an injection of phylloquinone, a 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°F (177ºC) until thoroughly heated (about 25-30 min.).

Abbreviations: mcg = microgram; tbsp = tablespoon; tsp = teaspoon