What Is Vitamin K? Food Sources, Deficiency and Daily Intake

Vitamins are necessary for cellular processes to continue normally. Some are produced by the body, while others must be obtained entirely from outside sources. If any vitamin is not consumed or produced in sufficient amounts, adverse medical conditions may develop.

Vitamin K is one of the 13 recognized vitamins. It occurs naturally in some vegetables. Vitamin K is also produced by beneficial bacteria living in our intestines (microbiota).

The main role of vitamin K in the body is in the clotting system, and deficiency causes clotting problems (bleeding). It also plays a role in bone formation and cardiovascular health. When discovered by Danish scientist Henrik Dam in the 1920s, it was named the Koagulation (clotting) vitamin because of its role in blood clotting.

Vitamin K is not a single type; according to its source, 3 main types can be described:

• Vitamin K1 (phylloquinone): from leafy green vegetables
• Vitamin K2 (menaquinone): produced by intestinal bacteria
• Vitamin K3 (menadione): a synthetic analog, 3 times more potent (effective)

Let Us Examine Vitamin K2 More Closely

Vitamin K1 (phytonadione) is important for clotting, while vitamin K2 is more important for calcium metabolism. We obtain vitamin K mostly from food; K1 is abundant in leafy vegetables. We obtain K2 from animal sources, and bacteria in our intestines synthesize a small amount. Vitamin K2 has 2 well-known forms: MK-4 and MK-7. From animals comes MK-4, and from bacteria MK-7, among the many subtypes of vitamin K2 with differing properties. Available vitamin supplements may contain MK-4 or MK-7. Another vitamin K form, synthetic K3 (menadione), is known to be toxic to the liver and is no longer used.

Normal Laboratory Value for Vitamin K: 0.13 - 1.19 ng/ml (adult)

Vitamin K deficiency is most commonly seen in liver failure (cirrhosis) and is one of the main causes of bleeding in cirrhosis. For this reason, patients with cirrhosis receive vitamin K injections at intervals determined by the severity of their cirrhosis.

Vitamin K Supplementation

Some studies suggest that vitamin K could be used to prevent or treat other health problems, but studies outside bleeding disorders have not yet reached a clear conclusion.

1. Bone Health
   Research suggests that vitamin K may improve bone health. Study results indicate that it may increase bone mineral density and reduce fracture rates in people with osteoporosis. Vitamin K may be especially effective when combined with vitamin D, a nutrient known to play a critical role in bone metabolism.
2. Cardiovascular Health
   Preliminary findings from animal studies suggest that vitamin K2 protects against atherosclerosis (hardening of the arteries). However, in a report published in Current Opinion in Lipidology in 2008, scientists noted that research results on vitamin K1 and heart disease were conflicting. One reliable source, The Natural Medicines Comprehensive Database , also found insufficient evidence to recommend vitamin K2 supplementation against coronary artery blockage.
3. Cognitive (Mental) Health
   Higher blood levels of vitamin K have been associated with stronger memory in older people.

Despite these findings, there is insufficient scientific evidence to support using vitamin K for any condition other than specific bleeding or blood-clotting problems!

Which Foods Contain Vitamin K?

Vitamin K is found most abundantly in leafy green vegetables. Just one serving (half a cup) of any of the following foods provides more than twice your daily vitamin K requirement:

- Spinach

- Turnip

- Collard greens

- Parsley

- Brussels sprouts

- Broccoli and lettuce are also rich in vitamin K.

Vitamin K Deficiency

Vitamin K is not water-soluble; it is a fat-soluble vitamin stored in the body. Vitamin K deficiency is therefore rare. Deficiency occurs when the body cannot properly absorb vitamin K through the intestinal tract or in certain chronic diseases, such as liver failure. It can also occur with cystic fibrosis, celiac and Crohn disease, long-term antibiotic use, blood-thinning medications or dialysis treatment.

Vitamin K deficiency can cause bleeding problems and bruising.

Warnings

Taking high amounts of vitamin K can be harmful to pregnant and breastfeeding women, patients with chronic kidney failure undergoing dialysis, and people with clotting problems caused by severe liver disease. Vitamin K can also interact with certain other supplements, including coenzyme Q10 and vitamin E. Vitamin K treatment must therefore be administered according to a physician’s dosage recommendation.