Vitamin K was discovered in 1929 and named for the German word koagulation, with Henrik Dam and Edward A. Doisy receiving the Nobel Prize for their research in 1943. But vitamin K is a multifunctional nutrient.
Vitamin K-1, or phylloquinone, is found in green leafy vegetables and used by the liver for blood coagulation in 10 hours.
Vitamin K-2, also known as MK-7 or menaquinone, comes from natto (fermented soybeans), organ meats, egg yolks and raw milk cheeses. It circulates throughout the body over a 24-hour period.
The Rotterdam Study in the 2004 Journal of Nutrition focused on the role of K-2 as an inhibitor of calcification in the arteries and the major contributor to bone-rebuilding osteocalcin. The study reported that K-2 resulted in a 50 percent reduction in arterial calcification, a 50 percent reduction in cardiovascular deaths and a 25 percent reduction in all causes of mortality. K-1 had no effect on cardiovascular health.
In his book Vitamin K2: The Missing Nutrient for Heart and Bone Health, Dr. Dennis Goodman describes why most Western diets are deficient in K-2. Dietary awareness of vitamin K has focused on anticlotting since warfarin was approved as a medicine. (It was initially used to kill rats.) Little attention was paid to any other nutritional importance this essential fat-soluble vitamin could provide.
Menaquinones (K-2 or MK) are synthesized in the human gut or intestinal microbiota from fermented foods, according to the Annual Review of Nutrition in 2009. Because they are rapidly depleted without dietary intake, natto or animal sources are needed for repletion. Aging and antibiotic use weaken the body's ability to produce K-2.
Bone health is dependent on vitamin K-2. Without it, the body does not use calcium and vitamin D-3 to activate osteoblasts to rebuild bone. Menaquinones cause cells to produce a protein called osteocalcin, which incorporates the calcium into the bone. Without it, calcium moves into the artery wall and soft tissues of the body, leading to hardening of the arteries and osteoporosis.
K-2's benefits have been known for years. In 1997, MJ Shearer discussed the roles of vitamins D and K in bone health and osteoporosis prevention in the Proceedings of Nutrition Society. The Osteoporosis International meeting in New Zealand in 2013 re-emphasized K-2's importance, proclaiming that the best treatment for osteoporosis is achieving a strong peak bone mass before age 30 and increasing vitamin K-2 food sources in the diet.
For those who have not acquired a taste for fermented soybeans, my nutrition mentor, Adelle Davis, recommended liver once a week.
Beef Liver with Pears, Bacon and Onions
Ingredients
½ pound grass-fed beef liver, sliced ½ inch thick
4 slices smoked bacon, cut into pieces
1 medium onion, sliced
2 fresh pears or plums, sliced
Salt and pepper to taste
Preparation
Remove any skin from outer edge of liver slices. Saute bacon in skillet until crispy.
Remove with slotted spoon. Add onion to bacon drippings and simmer until browned. Add pear slices and cook until soft. Place liver slices over onions and pear mixture. Cover skillet and cook 5 to 10 minutes just until liver is done. Serve with bacon sprinkled on top.
Makes 2 servings.
Nutrition information per serving: 292 calories, 24g protein, 13g carbohydrates, 7g fat, 65mcg sodium.
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