You Ask, I Answer: Vitamin K

What does Vitamin K do? What foods is it in?

-- Name Withheld
Brooklyn, NY

You kind of have to feel sorry for Vitamin K. It appears to be the least popular vitamin, and many people don't even appear interested in getting to know it better.

If Vitamin D is the life of the party, Vitamin K is standing by the punchbowl, futilely attempting to make small talk with other guests.

I would definitely suggest being familiar with it, though, since this nutrient plays a very important role in blood clotting and bone density.

You may wonder why its blood clotting properties are perceived as beneficial, particularly when one of the outed benefits of Omega-3 fatty acids is their blood thinning properties.

We come back to the ever-present ideal of balance.

Over-thinning of the blood is problematic, as it increases the risk of internal bleeding.

Additionally, without blood clotting factors, something a small cut could result in excessive blood loss.

Vitamin K helps with bone density by regulating calcitonin, a protein that locks calcium in the bone matrix, thereby making it more difficult for cells known as osteoclasts from breaking it down.

If osteoclasts are more active than osteoblasts (which help create new bone tissue), your risk of osteoporisis increases significantly.

What's interesting about this nutrient is that we get it two different ways.

K2, the more biologically active form, is synthesized by beneficial bacteria in our intestinal tract.

Since babies start off with bacteria-free intestines, they are given a Vitamin K shot within hours of being born.

The plant form -- K1 -- is found abundantly in leafy green vegetables. Although our intestinal bacteria produce some Vitamin K, we still need to get some from our diet.

A mere half cup of steamed kale, spinach, and collard greens each pack in six times the Daily Value!

A single cup of raw romaine lettuce provides three quarters of a day's worth.

Anyone who has ever been on blood-thinning medication (i.e.: warfarin, more commonly known as Coumadin) has been told to be mindful of their Vitamin K intake so as to prevent unwanted drug-nutrient interactions.

Here's why.

Warfarin, an anticoagulant, decreases clotting (this is why it is mostly prescribed to heart disease patients.)

A lot of people inaccurately think that the best thing to do when put on warfarin is completely eliminate Vitamin K from the diet.

Not so! The key is to keep vitamin K intake consistent.

Suddenly increasing Vitamin K consumption renders Coumadin ineffective, whereas decreasing it too much in a short amount of time will overly thin the blood.

Remember, too, that antibiotics kill all flora in the gut -- the negative AND positive bacteria (this includes the one that produces Vitamin K.)

Therefore, when on antibiotics, do not drastically alter your Vitamin K intake.

A clinical dietitian I know at New York City's Memorial Sloan Kettering Hospital recently told a most interesting anecdote about a patient who was put on coumadin.

A dietary recall revealed that her diet was very high in Vitamin K. Not a problem, but definitely important in the scheme of things.

Soon thereafter, she fell very ill, to the point where she stopped eating. Mind you, she was still on Coumadin.

In other words, her vitamin K drastically decreased (from about 1200% of the Daily Value a day to absolutely nothing).

To counteract the illness, she was given antibiotics (remember, she is still on Coumadin).

The antiobiotics wiped out gut flora.

So, she now had a high Coumadin dose (based on her standard Vitamin K intake) but no Vitamin K from her diet OR her intestinal tract.

Not surprisingly, she bled internally and had to be rushed into surgery.