Vitamin K

Vitamin K plays a key role in helping the blood clot, preventing excessive bleeding. Unlike many other vitamins, vitamin K is not typically used as a dietary supplement.

Vitamin K is actually a group of compounds. The most important of these compounds appears to be vitamin K1 and vitamin K2. Vitamin K1 is obtained from leafy greens and some other vegetables. Vitamin K2 is a group of compounds largely obtained from meats, cheeses, and eggs, and synthesized by bacteria.

Vitamin K1 is the main form of vitamin K available in the U.S.

Recently, some have looked to vitamin K2 to treat osteoporosis and steroid-induced bone loss, but the research is conflicting. At this point there is not enough data to recommend using vitamin K2 for osteoporosis.

Why do people take vitamin K?

Low levels of vitamin K can raise the risk of uncontrolled bleeding. While vitamin K deficiencies are rare in adults, they are very common in newborn infants. A single injection of vitamin K for newborns is standard. Vitamin K is also used to counteract an overdose of the blood thinner Coumadin.

While vitamin K deficiencies are uncommon, you may be at higher risk if you:

• Have a disease that affects absorption in the digestive tract, such as Crohn's disease or colitis
• Take drugs that interfere with vitamin K absorption
• Are severely malnourished
• Drink alcohol heavily

In these cases, a doctor might suggest vitamin K supplements.
Uses of vitamin K - for cancer, for the symptoms of morning sickness, for the removal of spider veins, and for other conditions - are unproven.

How much vitamin K should you take?
The recommended dietary allowance (RDA) includes the total amount of vitamin K you take in, both from food and other sources. Most people get enough vitamin K from their diets.

Group	Recommended Dietary Allowance
Children 0-6 months	5 micrograms/day
Children 6-12 months	10 micrograms/day
Children 1-3	15 micrograms/day
Children 4-6	20 micrograms/day
Children 7-10	30 micrograms/day
Children 11-14	45 micrograms/day
Girls 15-18	55 micrograms/day
Women 19-24	60 micrograms/day
Women 25 and up	65 micrograms/day
Women, pregnant or breastfeeding	65 micrograms/day
Boys 15-18	65 micrograms/day
Men 19-24	70 micrograms/day
Men 25 and up	80 micrograms/day

Vitamin K is well-tolerated even at high doses. Researchers have not set a maximum safe dose.

Can you get vitamin K naturally from foods?

Good natural food sources of vitamin K include:

• Vegetables like spinach, asparagus, and broccoli
• Beans and soybeans
• Eggs
• Strawberries
• Meat

What are the risks of taking vitamin K?

• Side effects. Upset stomach. At higher doses, vitamin K may trigger allergic reactions.
• Interactions. Many drugs can interfere with the effects of vitamin K. They include antacids, blood thinners, antibiotics, aspirin, and drugs for cancer, seizures, high cholesterol, and other conditions.
• Risks. You should not use vitamin K supplements unless your doctor tells you to. People using Coumadin for heart problems, clotting disorders, or other conditions may need to change their diets to control the amount of vitamin K they take in and should not use vitamin K supplements unless advised to do so by their doctor.