It’s been nicknamed “the forgotten vitamin”.

Yes, when it comes to vitamins, most of us only know our alphabet from A to E. But there’s another one that lies beyond: Vitamin K.

Even people who know about this vitamin think we’re getting plenty of it in our food, and it only serves one function in the body anyway, so there’s no need to consider it further.

Wrong on all counts.

Not only do we need this vitamin for its well-known role in blood clotting, but it’s now known to be needed for strong bones, flexible arteries and protection against cancer.

And the latest research shows it plays important roles in the brain, too.

As for getting enough in our food, even this is now questioned. While the average diet may be sufficient when it comes to blood clotting, it doesn’t provide enough of this nutrient for the other important functions.

Vital Roles in Brain Function

Vitamin K is actually a family of fat soluble nutrients called phylloquinone (K1) and a group of molecules called menaquinones (K2).

K1 is needed for blood clotting and brain health. K2 makes sure calcium is laid in bones and teeth — not in blood vessels where it contributes to plaque build-up in the cardiovascular system and the brain.

Both forms are important when it comes to mental function but research so far has focused on K1.

Within brain cells K1 is involved with the synthesis of sphingolipids. These are major components of nerve cell membranes and the myelin sheath that surrounds nerve cells. K1 also activates proteins that have important roles in the brain. Insufficient levels of K1 will disrupt wide-ranging functions of the nervous system.

Better Cognition, Memory and Behavior

A study of 320 cognitively healthy men and women aged between 70 and 85 found those with higher blood concentrations of K1 had better brain speed and verbal episodic memory (recall of events that occur within your experience, like where you left your car keys).

Of two studies that looked at dietary intake of K1 in seniors, the first found those with the highest intake scored better on a standard cognitive test and suffered fewer behavioral disorders. The second found the ones with the highest intake had fewer and less severe subjective memory complaints – i.e. they felt like their memories were working pretty well.

Blood Thinners Damage the Brain

Nearly seven million Americans at risk of heart attack or stroke are prescribed anticoagulant drugs such as warfarin to prevent harmful blood clots. These medications work by interfering with the action of vitamin K.

Does this increase the risk of dementia? Several studies sought to find out.

267 people with an average age of 83 undertook a cognitive test. Even after taking into account over a dozen factors that could influence the results, the risk of cognitive impairment was 17.4% higher in those who took blood thinning medication.

Another study of older people taking these drugs found less gray matter volume in the brain including the hippocampus. This means less ability to process information in a vital area for learning and memory and one of the first areas to be affected by Alzheimer’s.

In a third study, 7,133 cognitively healthy people aged 65 or above were followed over a period of ten years. Those taking anticoagulants performed significantly worse when it came to visual memory and verbal fluency tests.

K Shortfall in the Diet

1,379 adults living in Ireland were found to have an average daily K intake of 79 micrograms, well below the US adequate intake of 120mcg for men and 90mcg for women.

Katarzyna Maresz, PhD., President of The International Science and Health Foundation, writes that “Vitamin K, particularly as vitamin K2, is nearly nonexistent in junk food, with little being consumed even in a healthy Western diet.”

John Day is an MD-cardiologist and Medical Director of Heart Rhythm Services in Salt Lake City. He writes that “vitamin K1 and vitamin K2 deficiency is common in the Western world.”

It’s not hard to get a good intake of vitamin K provided you choose the right foods.

Best sources of K1 are green vegetables such as collards, turnip greens, spinach, kale and broccoli.

If you eat enough K1 to fulfill the body’s requirements, it can convert some of it to K2. However, it’s better insurance to get K2 from dietary sources. These include fermented foods such as sauerkraut and soybeans, gouda and brie cheese, and grass-fed meat and dairy products.


  1. http://www.ncbi.nlm.nih.gov/pubmed/22419547
  2. http://www.ncbi.nlm.nih.gov/pubmed/24108469
  3. http://www.ncbi.nlm.nih.gov/pubmed/23850343
  4. http://www.ncbi.nlm.nih.gov/pubmed/26274973
  5. http://www.ncbi.nlm.nih.gov/pubmed/26923488
  6. http://www.ncbi.nlm.nih.gov/pubmed/25151653
  7. http://www.ncbi.nlm.nih.gov/pubmed/26576841

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