What’s special about vitamin K2?

Vitamin K, a fat soluble vitamin discovered in the 1930’s, is best known for its role in blood coagulation or blood clotting.  This form is also known as vitamin K1 or phylloquinone.  However there is another form of vitamin K that hasn’t received as much attention until the 21st century – vitamin K2.  Vitamin K2, also known as menaquinone, is made by our intestinal bacteria and also is found in certain food sources.  Deficiencies of vitamin K1 are rare but deficiencies of vitamin K2 are more common.  It is the vitamin K2 form that seems to have far-reaching roles that appear to make a meaningful difference in the health of our hearts, bones and of prostate cancer. 

Vitamin K2 and heart health

One of the factors leading to heart disease is a buildup of atherosclerotic plaque which is made up of calcium, also known as vascular calcification. This plaque buildup accumulates in the soft tissues such as arteries and veins reducing their elasticity.  The reason for plaque buildup is due to damage to the soft tissues which results in deposition of calcium thus increasing the risk of a heart attack. 

There is a protein called matrix gla protein (MGP) that is activated by another protein called osteocalcin which vitamin K2 is necessary to trigger the activation of it.  MGP is responsible for protecting your blood vessels from calcification.  This activation of MGP by vitamin K2 is recognized as a potent factor in possibly preventing and reversing calcification in soft tissues leading to atherosclerosis.  People with low MGP levels such as diabetics, are at a greater risk of heart disease possibly due to their higher risk of arterial calcification. 

A 2009 study in Atherosclerosis showed that people with higher dietary intake of vitamin K2 had reduced coronary calcification.

Vitamin K2 and bone health

The nutrient we associate most with making our bones strong is the mineral calcium.  Vitamin D, magnesium intake and weight bearing exercise also have roles in keeping bones healthy.  Now we can also add vitamin K2 to this list. 

Vitamin K2 is more beneficial than vitamin K1 for bone health as the body prefers it to deposit calcium in the bones.  Vitamin K1 is mainly used for blood clotting.  Studies have shown that women with osteoporosis, the brittle bone disease, may benefit from vitamin K2 as it may help in maintaining bone mineral density resulting in fewer fractures. 

Vitamin K2 is required for activation of osteocalcin which is a protein secreted by osteoblasts.  Osteoblasts are cells that help build bone.  Osteocalcin which has been activated by vitamin K2, absorbs calcium into bones while osteoblasts integrate the calcium into bone matrix making the bones strong.  If vitamin D3 is combined along with vitamin K2, this will decrease osteoclasts which are cells that cause bone resorption. 

If you like natto, a fermented soy food high in vitamin K2, this may decrease the risk of fracturing a hip.  A study in Nutrition showed that Japanese women who consumed natto frequently had significantly less hip fractures than Japanese women who didn’t consume natto very often. 

Vitamin K2 and prostate cancer

A study in the American Journal of Clinical Nutrition showed that a higher intake of menaquinones or vitamin K2 resulted in reducing prostate cancer risk, particularly of advanced prostate cancer.  The type of food containing vitamin K2 or menaquinones that appeared to be most beneficial were fermented dairy products such as cheese.  Cheese is the predominant source of menaquinones.  In fact, vitamin K2 from dairy products had more of an impact on the incidence of advanced prostate cancer than vitamin K2 coming from meat products. 

A 2010 follow-up study also demonstrated that possibly consuming a regular dietary intake of vitamin K2, particularly of cheese, may have a positive effect of reducing incidence and mortality of lung and prostate cancer in men. 

Food sources of vitamin K2

The primary food sources of vitamin K2 are animal sources – liver is the richest meat source but chicken, beef, ham and egg yolk contain smaller amounts.  Hard cheeses made from whole milk are also valuable sources of vitamin K2.  The only vegetarian source is natto.  Natto is a fermented soy product made from a specific strain of bacteria used in the fermentation process. 

Many of the rich food sources of vitamin K2 are also high in saturated fat which may contribute to heart disease. If a person is having their blood lipids routinely monitored and they are consuming sources of vitamin K2 in moderate amounts, they should be able to add these foods to their daily diet. 

Vitamin K1 comes mainly from green leafy vegetables such as spinach, kale, turnip greens and collards, vegetable oils, broccoli, Brussels sprouts, cauliflower and cabbage.

In summary

Here is a side-by-side comparison between vitamin K1 and vitamin K2:

 

Vitamin K1

Vitamin K2

Also known as:

Phylloquinone

Menaquinone

Role

Necessary for blood to clot

Beneficial for heart, bone and prostate cancer

Food Sources

Green leafy vegetables such as spinach, kale, romaine, collards, turnip greens

Liver, egg yolks, hard cheeses and natto

Recommended Dietary Allowance

Women – 90 mcg/day

Men – 120 mcg/day

Not yet determined

Deficiency

Very rare

More common