NUTRIENT ~ Vitamin K

Vitamin K helps to make various proteins that are needed for blood clotting and the building of bones.

Vitamin K is a fat-soluble vitamin that comes in two forms. The main type is called phylloquinone, found in green leafy vegetables like collard greens, kale, and spinach. The other type, menaquinones, are found in some animal foods and fermented foods. Menaquinones can also be produced by bacteria in the human body. Vitamin K helps to make various proteins that are needed for blood clotting and the building of bones. Prothrombin is a vitamin K-dependent protein directly involved with blood clotting. Osteocalcin is another protein that requires vitamin K to produce healthy bone tissue. Vitamin K is found throughout the body including the liver, brain, heart, pancreas, and bone. It is broken down very quickly and excreted in urine or stool. Because of this, it rarely reaches toxic levels in the body even with high intakes, as may sometimes occur with other fat-soluble vitamins.

Antibiotic medicines may destroy vitamin-K-producing bacteria in the gut, thereby potentially decreasing vitamin K levels, especially if taking the medicine for more than a few weeks. People who have a poor appetite while using long-term antibiotics may be at greater risk for a deficiency, and may benefit from a vitamin K supplement. People who are taking blood-thinners, such as warfarin (Coumadin), should avoid suddenly beginning to eat more or fewer foods containing vitamin K, as this vitamin plays a vital role in blood clotting.

Because vitamin K is fat-soluble, it is best to eat vitamin K foods with some fat to improve absorption. So, drizzle some olive oil or add diced avocado to your favorite leafy green salad!Vitamin K deficiency in adults is rare, but may occur in people taking medications that block vitamin K metabolism such as antibiotics, or in those with conditions that cause malabsorption of food and nutrients. A deficiency is also possible in newborn infants because vitamin K does not cross the placenta, and breast milk contains a low amount. The limited amount of blood clotting proteins at birth increases the risk of bleeding in infants if they are not given vitamin K supplements.

AI: An “adequate intake” (AI) is used when there is not enough evidence to establish a Recommended Dietary Allowance (RDA). The AI amount is estimated to ensure nutritional adequacy. For adults 19 years and older, the AI for vitamin K is 120 micrograms (mcg) daily for men and 90 mcg for women and for those who are pregnant or lactating.

Some Plant-based Food Sources of Vitamin K

PHYLLIQUINONEMENAQUINONE
collard greensnatto: fermented soybeans
turnip greens
kale
spinach
broccoli
brussels sprouts
cabbage
lettuce
soybean oil
canola oil
Source: Harvard University Nutrition Source