Vitamin K plays a key role in our blood’s ability to form clots. It’s one of the less glamorous vitamins, more rarely discussed than its peers and, although it’s usually referred to as a single substance, it comes in two natural varieties — K1 and K2 — and one synthetic one, K3. People typically cover their requirements of vitamin K through diet, so it’s rarely seen in supplement form, but we’ll also look at some situations that might require an extra input of vitamin K.

The ‘K’ in vitamin K stands for Koagulations-vitamin, Danish for ‘coagulation vitamin’. This is a pretty big hint as to what these vitamers — the term used to denote the various chemically-related forms of a vitamin — help our bodies do. Vitamin K is involved in modification processes that proteins undergo after they have been synthesized, and these proteins then go on to perform clotting wherever it is needed in our blood. Apart from this, vitamin K is also involved in calcium-binding processes for tissues throughout our bodies, for example in bones.

Although we don’t need very high amounts of vitamin K to be healthy (relative to other vitamins), a deficiency of it is in no way a pretty sight. Without enough vitamin K, blood clotting is severely impaired, and uncontrollable bleeding starts occurring throughout our whole bodies. Some research suggests that a deficiency of this vitamin can also cause bones to weaken, leading to osteoporosis, or to the calcification of soft tissues.

What is vitamin K?

Chemically speaking, vitamin K1 is known as phytomenadione or phylloquinone, while K2 is known as menaquinone. They’re quite similar from a structural point of view, being made up of two aromatic rings (rings of carbon atoms) with a long chain of carbon atoms tied to one side. K2 has two subtypes, one of which is longer than the other, but they perform the same role in our bodies. The K1 variety is the most often seen one in supplements.

Vitamin K3 is known as menadione. It used to be prescribed as a treatment for vitamin K deficiency, but it was later discovered that it interfered with the function of glutathione, an important antioxidant and key metabolic molecule. As such, it is no longer in use for this role in humans.

They are fat-soluble substances that tend to degrade rapidly when exposed to sunlight. It also breaks down very quickly and is excreted quickly in the body, so it’s exceedingly rare for it to reach toxic concentrations in humans. Vitamin K is concentrated in the liver, brain, heart, pancreas, and bones.

Sources

As previously mentioned, people tend to get enough vitamin K from a regular diet.

Plants are a key synthesizer of vitamin K1, especially their tissues which are directly involved in photosynthesis; as such, mixing leafy or green vegetables into your diet is a good way to access high levels of the vitamin. Spinach, asparagus, broccoli, or legumes such as soybeans are all good sources. Strawberries also contain this vitamin, to a somewhat lesser extent.

Animals also rely on this vitamin for the same processes human bodies do, so animal products can also be a good source of it. Animals tend to convert the vitamin K1 they get from eating plants into one of the varieties K2 (MK-4). Eggs or organ meats such as liver, heart, or brain are high in K2.

All other forms of K2 vitamin are produced by bacteria who produce it during anaerobic respiration. As such, fermented foods can also be a good source of this vitamin.

Some of the most common signs of deficiency include:

• Slow rates of blood clotting;
• Long prothrombin times (prothrombin is a key clotting factor measured by doctors);
• Spontaneous or random bleeding;
• Hemorrhaging;
• Osteoporosis (loss of bone mass) or osteopenia (loss of bone mineral density).

Do I need vitamin K supplements?

Cases of deficiency are rare. However, certain factors can promote such deficiencies. Most commonly, this involves medication that blocks vitamin K metabolism as a side-effect (some antibiotics do this) or medical conditions that prevent the proper absorption of nutrients from food. Some newborns can also experience vitamin K deficiencies as this compound doesn’t cross through the placenta from the mother, and breast milk only contains low levels of it. Due to this, infants are often given vitamin K supplements.

Although it is rare to see toxicity caused by vitamin K overdoses, it is still advised that supplements only be taken when prescribed by a doctor. Symptoms indicative of vitamin K toxicity are jaundice, hyperbilirubinemia, hemolytic anemia, and kernicterus in infants.

Vitamin K deficiencies are virtually always caused by malnourishment, poor diets, or by the action of certain drugs that impact the uptake of vitamin K or its role in the body. People who use antacids, blood thinners, antibiotics, aspirin, and drugs for cancer, seizures, or high cholesterol are sometimes prescribed supplements — again, by a trained physician.

How was it discovered?

The compound was first identified by Danish biochemist Henrik Dam in the early 1930s. Dam was studying another topic entirely: cholesterol metabolism in chickens. However, he observed that chicks fed with a diet low in fat and with no sterols had a high chance of developing subcutaneous and intramuscular hemorrhages (strong bleeding under the skin and within their muscles).

Further studies with different types of food led to the identification of the vitamin, which Dam referred to as the “Koagulations-Vitamin”.

Some other things to know

Some of the bacteria in our gut help provide us with our necessary intake of vitamin K — they synthesize it for us. Because of this, antibiotic use can lead to a decrease in vitamin K levels in our blood, as they decimate the populations of bacteria in our intestines. If you’re experiencing poor appetite following a lengthy or particularly strong course of antibiotics, it could be due to such a deficiency. Contact your physician and tell them about your symptoms if you think you may need vitamin K supplements in this situation; it’s not always the case that you do, but it doesn’t hurt to ask.

Another step you can take to ensure you’re getting enough vitamin K is to combine foods that contain a lot of it with fats — as this vitamin is fat-soluble. A salad of leafy greens with olive oil and avocado is a very good way of providing your body with vitamin K and helping it absorb as much of it as possible.