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Vitamin K and your healthFairly neglected as an essential nutrient, vitamin K was for a while known mostly as a skin cream ingredient that was supposedly making tiny unsightly veins in the upper skin layer disappear. However, its body function is much more serious, and recent research suggest that there are still important thing to learn about this somewhat obscure nutrient.
Till recent, it was officially considered that food supply of vitamin K comfortably exceeds average human needs. Estimated average daily intake was 0.3mg-0.5mg, with the estimated adequate intake set at ~0.1mg. Current data suggests considerably lover average intake, roughly at the level of what is considered adequate.
Also, previous estimates of about half of the body's supply of vitamin K coming from friendly intestinal bacteria, now seems to be reduced to only a fraction of what is available from food sources. Most Americans have their vitamin K intake almost exclusively in the plant form of vitamin K (K1, or phylloquinone), and almost no bacteria-produced K2 (menaquinone).
Since those are only the estimates of averages, chances are that good portion of the population has sub-optimal intake of vitamin K. Possible deficiency symptoms are compromised blood clotting, bruising, osteoporosis, cardiovascular disease, calcification, delayed development in infants17, and others.
Toxicity from vitamin K overdose, or excessive intake occurs only with its synthetic form (K3), and includes liver impairment, hemolytic (red blood cell) anemia and brain damage in infants. Excessive doses of the natural form of vitamin K can cause jaundice in infants.
Vitamin K DRI (Dietary Reference Intakes, the most recent set of dietary recommendations set by the government) for an average healthy adult female is 0.09mg (90mcg) a day, and 0.12mg (120mcg) for a male.
Best natural vitamin K food sources are green leafy vegetables, followed by cheese, yogurt, fish liver oils, etc.