Vitamin K is essential for clotting, bone health, and preventing calcification of your arteries. Most Americans don’t meet even the minimal intake guidelines for Vitamin K.

Vitamin K was first identified to be essential for normal clotting, (vitamin K as in German for koagulation), otherwise one might bleed to death after a minor cut.

Over time, we have discovered that vitamin K is also essential for bone and artery health. Without adequate vitamin K, bones lose calcium, increasing your risk for osteoporosis and a debilitating fracture later in life. Arteries become stiff and hard as they can’t get rid of calcium from their walls, leading to atherosclerosis and heart disease.

There are two forms of vitamin K: K1 and K2. K2 is the more physiologically active of the two forms, but much more challenging to get in your diet. Vitamin K1 comes from eating green leafy vegetables and is fairly easy to get from food. Both forms are beneficial to your health.

How much Vitamin K1 do you need for your bones and arteries?

  • The minimum for proper clotting is around 100 mcg of vitamin K1 per day (90mcg for women, and 120 mcg for men). Many Americans don’t even achieve this minimal intake.
  • Yet for your bones and arteries, they function much better with at least 200 mcg of Vitamin K1 daily, and most experts in this field suggest that for optimum function you get 500 to 1,000 mcg daily.

Here are some great sources of Vitamin K1:

Food Content                               Measure             mcg of K1

Kale, cooked, drained                              1 cup                 1,062

Collards, cooked drained                        1 cup                 1,059

Spinach, cooked (or ~7 cups raw)           1 cup                   889

Beets, cooked                                            1 cup                   697

Broccoli, cooked                                        1 cup                   220

Brussels sprouts, cooked                         1 cup                   219

Onions, raw                                                 1 cup                  207

Parsley                                                        10 sprigs             164

Cabbage, cooked (or ~ 3 cups raw)          1 cup                 163

Asparagus, cooked                                      1 cup                 144

Lettuce, iceberg                                           1/4 head              3

The bottom line is that nearly everyone should be able to meet their needs for Vitamin K1 with food.

However, there is one contraindication to consuming vitamin K, and that applies to people receiving certain anti-coagulation drugs that decrease clotting. The drug warfarin (Coumadin) decreases vitamin K coagulation activity and taking extra vitamin K can block the medication’s action. In a person requiring this form of medication, taking extra Vitamin K could cause life-threatening clot formation. So, for people taking this type of medication, they should speak to their own physician managing their care before trying to increase their vitamin k intake, either from food, or from supplements. My goal with my own patients on warfarin is that they should eat a consistent amount of green leafy vegetables every day and modify their medication dosage as needed, but this can only be done with your doctor testing for the impact of vitamin K rich foods on your drug activity and blood levels, absolutely not something a person should try on their own.

As noted above, vitamin K2 is the more potent form of vitamin K, and provides additional bone and cardiovascular health benefits. This is especially important for people who already have known heart disease, or known bone loss and osteopenia or osteoporosis.

In the Rotterdam Study with 4800 subjects followed over 10 years, greater dietary vitamin K2 intake is associated with a decreased risk for cardiovascular disease. They compared people with less than 21 mcg of vitamin K2 per day, with 21 to 32 mcg per day, to more than 32 mcg/day. Those with more than 32 mcg per day had 57% less risk for heart disease than those with less than 21 mcg days.

For bone health, studies have shown that people likely need at least 50 mcg of vitamin K2 per day to lower their risk for osteoporosis and bone density loss, and up to 200 mcg might be a more optimal dose for people with osteopenia or heart disease.

In the table below, you can see foods that are high in vitamin K2. Apart from Natto (fermented soy), the amount needed to achieve at least 32-50 mcg a day for a heart disease benefit would be difficult to do with food alone.

You would have to consume a very large amount of saturated fat from either:

  • 14 tablespoons of butter
  • 5 ounces of raw-unpasteurized cheese that are aged and probiotic rich (some might call fermented cheese smelly)
  • 8 egg yolks

And to reach more than 200 mcg per day vitamin K2 intake to achieve a bone health benefit seems only achievable with a very large serving of natto (fermented soy).

FOOD                       Serving size        Vitamin K2 mcg/100 mg

Natto (fermented soy)      0.5 cups                        257

Munster cheese              1.5 ounces                       34

Camembert cheese        1.5 ounces                        27

Aged gouda cheese        1.5 ounces                        20

Roquefort cheese           1.5 ounces                        16

Swiss cheese                    1.5 ounces                       3.5

Mozzarella cheese          1.5 ounces                        1.7

Butter                                7 tablespoons                  15

Egg yolk (large)                 4                                        15

Animal meat                     3.5 ounces                       4.5

Fish                                   3.5 ounces                        0.9

Milk                                   3.5 ounces                        1.1

Green vegetables             2/3 cup                             0

Sauerkraut                        2/3 cup                             5

Fruit                                   2/3 cup                              0

Bread                                2 slices                               0

There is some conversion of vitamin K1 to vitamin K 2 both in the human intestinal tract and intracellularly. The challenge is that the amount of conversion varies from person to person, and it remains unknown if this conversion is adequate to meet the benefits provided by adequate vitamin K2 intake.

Specific drugs block the conversion of vitamin K1 to K2, in particular statin medications, alendronate (Fosamax), and warfarin (Coumadin). Anyone on these medications need to take extra precaution to add extra vitamin K2 daily, but if you are taking a medication such as warfarin, you must talk to your physician in advance to see if this is appropriate for you, be super consistent with your daily dosage, and work with your physician to modify your warfarin dosage appropriately.

Supplements provide a convenient way to increase intake for both vitamin K1 and K2. You can find vitamin K added to either multivitamins, fish oil, and vitamin D supplements.

While you should be able to meet your needs for vitamin K1 easily enough with green leafy vegetables, unless you enjoy eating ¼ cup of natto daily (this is definitely an acquired flavor), you’ll need to consider a supplement to meet your optimal intake.

Below are the supplements that I use with my patients to boost their vitamin K1 and K2 intake:

For people with advanced osteoporosis, there are studies that have used dramatically higher dosages of vitamin K2 daily to treat bone loss and risk for bone fractures. Dosages up to 15 mg to 45 mg daily have been used, but you should always discuss this dosing option with your own physician to clarify what is the best medical option for you.

Summary:

Everyone at the minimum should ensure they meet their needs for vitamin K1 and get at least 250 mcg to 1000 mcg daily, something that you should be able to do by eating one cup of green leafy vegetables every day.

For people at high risk for bone loss or heart disease, especially for those who already have been diagnosed with either of these problems, adding vitamin K2 from either food (natto daily) or a supplement is appealing and worth discussing with your own medical provider.

I wish you the best of health!

Steven Masley, MD, FAHA, FACN, FAAFP, CNS

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