Vitamin K

By Dietitian, Juliette Kellow BSc RD

How much you need each day:

There’s no RNI. A safe intake is considered to be 1mcg per kilogram of body weight. For example, a person who weighs 70kg will need about 70mcg of vitamin K each day.

Why you need it:

Vitamin K helps the blood to clot after a cut or injury. Unlike most of the other vitamins, which need to be supplied by the diet, about half of the vitamin K we get is made in the large intestine by bacteria.

Good food sources:

As well as being made in the body, foods containing vitamin k include green leafy vegetables, liver, milk, vegetable oils, wholegrains, oats and meat.

Too little:

As our bodies make vitamin K, a deficiency is rare but may occur in people who are given drugs that destroy gut bacteria, for example, prolonged use of antibiotics. A deficiency can cause easy bruising and a prolonged bleeding time after an injury. Babies are given an injection of vitamin K when they’re born as their gut is free of bacteria and breast milk doesn’t contain much of this vitamin.

Top tip:

Probiotic drinks and yoghurts that contain acidophilus bacteria help to boost levels of gut bacteria, ensuring you make enough vitamin K. If you are taking a course of antibiotics, it’s a good idea to include products like these in your diet, as some drugs can inhibit the absorption of this vitamin.

How to get enough: