What’s the vitamin that doesn’t get the respect (or recognition) it deserves? Vitamin K2, also called menaquinone.
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Over the last two decades, studies indicate that vitamin K2 plays a significant role in cardiovascular health — preventing osteoporosis (K2 helps form strong bones) and helping reduce risk of prostate cancer. It may also be beneficial in preventing wrinkles and premature aging.
The two faces of vitamin K
There are two forms of the fat-soluble vitamin K: K1 and K2.
Vitamin K1, or phylloquinone, is used by the liver and plays an important role in maintaining healthy blood clotting function. Found primarily in dark, leafy greens, top sources of K1 include kale, spinach, mustard greens, collard greens, Swiss chard, turnip greens, parsley, broccoli, Brussels sprouts and romaine lettuce.
Vitamin K2 goes straight to vessel walls, bones and soft tissues. Produced by grass-fed animals and lactic acid bacteria, vitamin K2 is naturally present in fermented foods such as sauerkraut, cheese and Japanese natto (soybeans fermented with bacillus subtilis, a soil bacterium) — an exceptionally high source of K2 (about 1,103 mcg per 3-1/2 ounce serving).
An intimate relationship: Vitamin K2, vitamin D and calcium
In her book Vitamin K2 and the Calcium Paradox, Dr. Kate Rhéaume-Bleue, a naturopathic physician and Canadian radio and television health expert, describes this phenomenon called the calcium paradox: “a mysterious concurrent calcium deficiency (in the skeleton) and calcium excess (in the arteries) that underlies two major health concerns of our time, osteoporosis and heart disease.”
How it works: Vitamin D promotes bone health by helping you absorb calcium. However, you need vitamin K2 to get calcium to where your body needs it and to prevent it from being deposited in the wrong places. For example, K2 activates a special protein called osteocalcin, which directs the calcium to the “right” places, like your bones and teeth. K2 also activates another protein called matrix Gla-protein (MGP), which sweeps calcium out of the “wrong” places — such as soft tissues, including veins and arteries — thereby preventing calcification, or “hardening” of the arteries.
Adequate consumption of K2 ensures strong bones and clear arteries; Rhéaume-Bleue suggests about 150-200 micrograms of K2 for the “average healthy person.” (More K2 may be required if you are supplementing with high doses of vitamin D). Without enough K2 in our diet to activate K2 proteins, like osteocalcin and MGP, we are — over time — susceptible to the calcium paradox, increasing our risk for osteoporosis, heart disease and cancer.
Under study: Vitamin K2
Heart health: In the Rotterdam study, researchers in the Netherlands tracked the vitamin K intakes of subjects between 1990 and 1993 and measured the extent of heart disease and failure (death from heart disease) in each subject, and how it related to K2 intake and arterial calcification. Researchers found calcification of the arteries to be the best predictor of heart disease. Those in the highest third of vitamin K2 intakes were 52 percent less likely to develop severe calcification of the arteries, 41 percent less likely to develop heart disease, and 57 percent less likely to die from it. Intake of vitamin K1 had no effect on cardiovascular outcome.
Bone health: Vitamin K2 helps to activate vitamin K-dependent proteins responsible for healthy tissues and bones. Several Japanese trials have shown that K2 prevented further bone loss in postmenopausal women and, in some cases, increased bone mass in women with osteoporosis.
Prostate cancer: Study results of the European Prospective Investigation into Cancer and Nutrition (EPIC) suggest that increased intake of vitamin K2 may reduce the risk of prostate cancer by 35 percent.
The X factor
In 1945, Dr. Weston Price, a dentist and author of the landmark book Nutrition and Physical Degeneration, described a new vitamin-like activator — which he called “Activator X” — that played an important role in the assimilation of minerals, protecting against tooth decay and preventing calcification of the arteries leading to heart disease. His testing revealed that “Activator X” was present in butterfat, the organs and in the fat of animals grazing on green grass.
Activator X was later identified as vitamin K2.
Why are grass-fed animals an important source of K2? Because vitamin K1 is found in the green tissues of rapidly growing green plants, including grass. When animals eat grass, their tissues — including mammary glands (think dairy) — convert part of K1 into vitamin K2 (though the ability to make this conversion varies among species).
As a fat-soluble vitamin, K2 works synergistically and is most effective when consumed with two other fat-soluble activators: vitamins A and D. For example, Price found the combination of cod liver oil (high in vitamins A and D) and grass-fed butter (high in vitamin K2) to be superior to that of taking just cod liver oil.
Best food sources of vitamin K2
According to researcher Christopher Masterjohn, the following fermented foods and grass-fed animal or dairy products contain the highest amounts of vitamin K2:
- Goose liver pâté
- Hard cheeses — Gouda contains the highest amount
- Soft cheese — Brie is a good choice
- Egg yolk (from pastured chickens)
- Butter from grass-fed or pasture-raised cows (commercial butter from grain-fed cows will contain notably lower levels of K2)
- Chicken liver (ideally from free-roaming, all-natural chickens)
- Chicken breast
- Chicken leg
- Ground beef (medium-fat)
- Calf liver