Vitamin K

Doctors have long used vitamin K, which promotes blood clotting, to help heal incisions in surgical patients and to prevent bleeding problems in newborns.  This vitamin also aids in building strong bones and may be useful for combating the threat of osteoporosis.

In the 1930s Danish researchers noted that baby chickens fed a fat-free diet developed bleeding problems.  They eventually solved the problem with an alfalfa-based compound that they named vitamin K, for Koagulation.  Scientists now know that most of the body's vitamin K needs are met by bacteria in the intestines that produce this vitamin, and only about 20% comes from foods.  Deficiencies are rare in healthy people, even though the body doesn't store vitamin K in high amounts.  Natural forms of vitamin K come from chlorophyll--the same substance that gives plants such as alfalfa their green color.  Other names for vitamin K are phytonadione and menadiol.

The single nutrient sets in motion the entire blood-clotting process as soon as a wound occurs.  Without it, we might bleed to death.  Researchers have discovered vitamin K plays a protective role in bone health as well.

Doctors often recommend preventive doses of vitamin K if bleeding or hemorrhaging is a concern.  Though not yet widely accepted treatment, vitamin K may provide great benefits for those suffering from osteoporosis.  Some studies show it helps the body make use of calcium and decreases the risk of fractures.  Vitamin K may be especially important for bone health in older women.  It is included among the ingredients in many bone-building formulas.

Because vitamin K needs are met in the body, the daily RDA is low: 80 mcg for men over the age of 25 and 65 mcg for women over age 25.

It is hard to get too much vitamin K because it's not abundant in any one food (except leafy greens).  Although even mega-doses are not toxic, high doses can be dangerous if you're taking anti-coagulants.  Large doses also may cause flushing and sweating.

Leafy green vegetables, including--per cup of vegetable--kale (547 mcg), Swiss chard (299 mcg), and turnip greens (138 mcg), are richest in vitamin K.  Broccoli, spring onions, and Brussels sprouts are also good sources.  Other foods with some vitamin K are pistachios, vegetable oils, meats, and dairy products.  A cup of kale provides the equivalent of more than five 100 mcg tablets of vitamin K.

According to a Tufts University study, a cup of green tea contains virtually no vitamin K.