Vitamin K
Little-known but essential, vitamin K helps blood to clot, helping keep blood in blood vessels. Most vitamin K is produced by bacteria in the gut, although there are also a few vitamin K-containing foods.
How much vitamin K do we need?
|
|
Age
(years)
|
AI*
Vitamin K
(µg/day)
|
|
Infants
|
7-12 months
|
2.5
|
|
Children
|
1-3
|
25
|
|
|
4-8
|
35
|
|
Boys
|
9-13
|
45
|
|
|
14-18
|
55
|
|
Girls
|
9-13
|
45
|
|
|
14-18
|
55
|
|
Men
|
19-70+
|
70
|
|
Women
|
19-70+
|
60
|
|
Pregnant and breastfeeding women
|
14-18
|
60
|
Who needs more and why?
Newborn babies – babies are usually given a vitamin K injection at birth, because their guts contain very few vitamin K-producing bacteria. Without it, babies are at risk of excessive bleeding.
Which foods contain vitamin K?
As well as in the gut, it is found in green, leafy vegetables (such as spinach, broccoli, brussels sprouts, cabbage, lettuce), soybean and canola oils. Some milk products are fortified with vitamin K.
Medications and vitamin K
Some medications, such as Warfarin, aim to reduce blood clotting. These work in direct contrast to vitamin K, which helps blood clot. Those on Warfarin-type medications should try to eat similar amounts of vitamin K-containing foods each day. If any major changes are made to vitamin K-containing foods eaten regularly, this may affect bleeding times and medication levels may need to be adjusted. This needs to be monitored by a doctor, with support from a registered dietitian. Such changes may occur:
§ during the summer if more salad vegetables, i.e. lettuce, are being eaten
§ when certain high vitamin K vegetables are in season, e.g. Brussels sprouts
§ if a cooking oil is changed to a high vitamin K oil, such as canola or soya.