Vitamin K is a group of fat-soluble vitamins that have a common chemical structure and are stored in the body’s fatty tissue and liver. The two types of vitamin K that are most commonly found in our diets are vitamin K1 (also called phylloquinone or phytonadione) and vitamin K2 (also called menaquinones).
Because vitamin K1 and vitamin K2 absorb in the body differently and transport to body tissues differently, they may have different effects on your health.
- Found in foods such as green leafy vegetables, dairy products and vegetable oils.
- Considered the plant form of vitamin K. However, it is also produced commercially to treat conditions related to excessive bleeding.
- Essential to the circulatory system. Without it, the liver cannot produce the molecules that ensure coagulation of the blood.
- Serious deficiency of vitamin K1 poses a risk of hemorrhage.
- Average recommended values for vitamin K1 intake are 0.08 milligrams for women and 0.12 milligrams for men.
- Made by the bacteria in the gut, which can convert vitamin K1 to vitaminK2.
- Found in highly fermented foods such as sauerkraut, natto (a Japanese food made of fermented soybeans), cheese, liver, yogurt and dietary supplements.
- Supplements the vitamin K1 the body obtains through diet.
- Like vitamin K1, acts as a protein activator and assists in blood coagulation.
- More often recognized for its essential role in maintaining arterial flexibility.
- Activates a protein called matrix Gla-protein (MGP), which contributes to the elimination of calcium in the arteries and thus delays the onset of high blood pressure.
- Has a role in calcium metabolism and helps to protect bone density. Without vitamin K2, calcium would not be absorbed by the protein osteocalcin for subsequent binding to and strengthening of the bone matrix.
- Exact recommended values for vitamin K2 unclear. Currently, it is assumed that about 180-200 micrograms is a sufficient daily dose.
What is vitamin K3?
Vitamin K3 (menadione) is a synthetic version of vitamin K made in the lab. Unfortunately, research has shown that artificial vitamin K3 interferes with one of the body’s naturally occurring antioxidants, glutathione, which can increase oxidative damage to cells. Vitamin K3 may cause liver toxicity, jaundice and anemia from ruptured blood cells. This form of vitamin K is therefore not sold as a dietary supplement.
What are signs and symptoms of Vitamin K deficiency?
Signs and symptoms of vitamin K deficiency may include:
- Bruising, especially around the head or face
- Bleeding episodes, such as bleeding from the umbilical cord, around the belly button, nose and mouth, penis (if circumcised) and at vaccination sites
- Paleness, which may be noticeable in the gums of darker-skinned infants
- Yellowing of the skin and eyes that is occurring for three or more weeks after birth. This is distinct from newborn jaundice, which typically clears by the time the baby is 2 weeks old.
- Stool that is bloody, dark or sticky like tar
- Blood in the urine
- Excessive sleepiness
Vitamin K deficiency in adults is rare but common in premature newborns. Newborns are often given a single dose of vitamin K to prevent vitamin K deficiency bleeding (VKDB), which is a rare condition that occurs when the blood can’t clot.
What are good sources of vitamin K?
Most people get enough vitamin K through their diet. The best sources of vitamin K are dark green leafy vegetables, such as spinach, parsley, broccoli, kale, cabbage, Brussels sprouts and salad greens. Other good sources include green beans, avocados, kiwis, vegetable oils, yogurt, fermented food/drinks and some cheeses.