What is vitamin K1?

There are two main types of vitamin K.

Vitamin K1 (phylloquinone) is a fat-soluble vitamin that plays an important role in blood clotting.

This 'anti-haemorrhagic' vitamin is also essential for calcification or bone formation.

It is produced by bacteria in the intestinal flora and is found in plant foods, supplements and medicines.

Vitamin K2 (menaquinone) is good for soft tissues.

It is also partly produced by the body and found in food.

There is vitamin K3 (menadione), but this is a synthetic form (which becomes vitamin K2).

What are the benefits of vitamin K1?

Vitamin K1 is important for bone health.

It promotes the action of a protein hormone that is part of the bone structure, osteocalcin.

According to the European Food Safety Authority, food supplements with doses of 11µg (micrograms)/100g of vitamin K contribute to normal bone function.

What are the indications and contraindications for vitamin K1?

As a medicine, vitamin K1 is only used to help blood clotting when there is a deficiency or risk of deficiency.

These are special situations:

• Newborn babies and some women before childbirth
• People undergoing treatment that may cause bleeding (strong antibiotics, anticoagulants, medicines that prevent the normal absorption of vitamin K) 
• Diseases that limit vitamin K absorption
• Blood clotting problems
• Liver and gallbladder problems

Doctors give vitamin K1 in the form of an injectable, drinkable solution (pipettes and ampoules).

The use of any anticoagulant should be reported.

In the Summary of Product Characteristics (SPC) for injectables, the main contraindications are allergies to the components of the drug (except vitamin K).

Which foods are rich in vitamin K1?

Foods rich in vitamin K1 include dark green vegetables such as spinach and broccoli.

Vitamin K1 is also naturally found in cauliflower, Brussels sprouts, kale, collard greens, asparagus, green beans, Swiss chard or endive, and various types of lettuce.

Several plants are excellent sources of vitamin K1, especially parsley, watercress and fennel, as well as thyme and basil.

Some fruits also provide vitamin K1, such as blueberries, kiwi, pomegranate and apples.

Finally, vitamin K1 is found in soya and soya oil.

Although some foods should be eaten raw to get the most out of vitamin K1, it is not sensitive to cooking.

On the other hand, keep foods fresh and away from light.

Why give vitamin K1 to a child?

Newborn babies should be given vitamin K1 to prevent bleeding.

At birth, people have almost no vitamin K1 because there are not enough intestinal bacteria to produce it.

Newborns who are not at risk are given a single intramuscular injection shortly after birth or an oral treatment in three doses: at birth, a few days later and one month later.

Premature and full-term babies who are at risk are given an injection at birth and further doses later if needed.

Full-term babies who are not at risk and are exclusively breastfed also receive three doses of vitamin K1 orally.

Breast milk has very low levels of vitamin K1.

These treatments are both effective and safe.

What are the recommended intakes and doses of vitamin K1?

Recommended dietary intakes of vitamin K1 vary according to health organisations.

According to the National Agency for Food, Environmental and Occupational Safety and Health (ANSES), adult men and women need 79 µg of vitamin K1 per day.

Needs do not increase during pregnancy or breastfeeding.

Also according to ANSES, the vitamin K1 requirement for infants is 5 µg/day and 10 µg/day after six months of age.

Children and adolescents require between 29 µg/day and 45 µg/day.

The dosage of oral or injected vitamin K1 depends on the drug.

In infants, single doses are usually 1 or 2 mg and oral doses are 2 mg.

They are much lower for premature babies weighing less than 2.5 kg.

In adults, it is not recommended that vitamin K treatments exceed 25 µg per day (Anses), but dosages may vary from patient to patient.

What are the risks and signs of vitamin K1 deficiency?

While a lack of vitamin K1 in infants puts them at risk of bleeding, there is no risk of deficiency in healthy adults.

A varied diet covers our vitamin K1 needs.

People who are vitamin K1 deficient and require treatment suffer from diseases (bowel, liver, etc.) and the main symptoms are very frequent bleeding and an increased susceptibility to bruising.

What are the side effects of overdose?

Excess vitamin K1 from natural sources has no side effects.

Even if a healthy person eats large amounts of vitamin K-rich foods every day, they don't absorb all of it and the excess is excreted by the body.

On the other hand, people on anticoagulant treatment should watch their diet, and vitamin K1 treatments are contraindicated if anticoagulants are being used.