– Fat-Soluble Vitamins –
15: VITAMIN K
Vitamin K cannot be made by our bodies, but not all vitamin K needs to be obtained from food, because bacteria in our gut can make it (as also is the case with biotin). Probably, about half our vitamin K needs can be made by gut bacteria.
Vitamin K is involved in the formation of special liver proteins, known as coagulation factors, which, when circulating in our blood, reduce the risk of haemorrhage or bleeding. Conversely, if you are susceptible to blood clotting, medication (usually warfarin) that interferes with the formation of these vitamin-K-dependent factors may be prescribed for you. If you are taking warfarin, you need to be particularly careful not to alter your intake of vitamin-K containing foods without close medical supervision.
Newborn babies can sometimes suffer vitamin K deficiency, as can people who do not absorb fat, since vitamin K is fat soluble. Those with liver disease may require more vitamin K.
VITAMIN K INTAKE
Safe and adequate daily intake of vitamin K (U.S.A.): Infants:Children and adolescents:Adults: 10-20 micrograms15-100 micrograms70-140 micrograms
Another way of expressing vitamin K requirement is to say that about 2 micrograms per kilogram of body weight per day are needed, but half of this could come from gut bacteria.
Toxic level of intake: Many milligrams of natural vitamin K can be ingested by healthy adults without adverse effects. Synthetic forms of vitamin K can be more of a problem in high dosages.
FIGURE 51: THE VITAMIN K CONTENT OF SOME FOODS
FOOD VITAMIN K
(micrograms per 100 grams of food)
Milk, cow’s, skim
less than 5
less than 5