Vitamin K is one of four fat-soluble vitamins that the body is capable of storing in its tissues. Vitamin K's primary function is to act as a catalyst for proteins, which help form blood clots. Vitamin K may also help promote bone health. The Institute of Medicine sets recommended daily allowances for vitamins and minerals. There is currently insufficient scientific evidence to set RDAs for vitamin K, although the IOM does provide an average intake, or AI -- an amount that is believed to support the nutritional needs for healthy individuals in each age group.
Infants and Children
Infants need very little vitamin K in the early stages of their lives. The AI for infants up to 6 months is just 2.0 micrograms per day. From ages 6 months to 1 year, infants need about 2.5 micrograms of vitamin K each day. At the age of 1 until 3, boys and girls need quite a bit more, with the AI set at 30 micrograms a day. Boys and girls ages 4 to 8 then need 55 micrograms a day.
Males
After the teenage years, males and females begin to need differing amounts of vitamin K due to differences in body size and hormone levels. Males ages 9 to 13 years need 60 micrograms of vitamin K each day, while 14- to 18-year-old males need 75 micrograms. From age 19 on, males typically need about 120 micrograms each day.
Females
From ages 9 to 13 and 14 to 18, females need the same amount of vitamin K as males, with the AI for each age group being 60 and 75 micrograms a day, respectively. Females then need quite a bit less vitamin K than males. The AI for females ages 19 and older is 90 micrograms a day.
Nursing Women
The IOM provides AI values for pregnant and nursing women, although they do not need any more vitamin K than non-pregnant and non-nursing women. Pregnant and nursing women ages 14 to 18 need about 75 micrograms of vitamin K each day, while older pregnant and nursing women need 90 micrograms. Some babies may be born with vitamin K deficiencies, and vitamin K shots just after birth are not uncommon.
Forms and Sources
Three forms of vitamin K exist, including vitamin K-1, vitamin K-2 and vitamin K-3. Vitamin K-1 is the primary dietary form, and is present in green leafy vegetables, beans and some oils such as canola and olive oil. Vitamin K-2 is in food as well -- mostly in meats and dairy products. Vitamin K-3 is a synthetic form of vitamin K that is not used as a supplement for humans. You can take a vitamin K-1 or a vitamin K-2 supplement, either separately or in a multivitamin.
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