When it comes to vitamins and minerals, there are some we’re all pretty familiar with, like vitamin C, vitamin D, iron, and magnesium. But other vitamins receive far less attention – like vitamin K. Many people have never heard of vitamin K, yet this vital nutrient plays a key role in health, and there are many experts who believe it could be the missing link between diet and disease.
So what exactly is vitamin K? Why is it important, and how can we make sure we’re getting enough of it? Here’s everything you need to know about vitamin K.
What is vitamin K?
Vitamin K is actually a group of vitamins; the most important of which are vitamins K1 and K2. Vitamin K1 comes from plants and is the main source of dietary vitamin K. A lesser source of vitamin K is vitamin K2, which is mostly found in certain animal-based and fermented foods.
Vitamin K was first ‘discovered’ in 1929 when it was found to be a vital nutrient for blood clotting – or coagulation. Without vitamin K, the body is unable to make prothrombin (which is a protein and clotting factor). The initial discovery was first reported in a German scientific journal, where it was named “Koagulationsvitamin“. This is where the “K” in vitamin K comes from.
The Canadian dentist Weston Price, who was known in the early 20th century for his views on the ways that nutrition affects health, is also credited with discovering vitamin K. He reported that many diets were high in an unknown vitamin which seemed to protect against both tooth decay and chronic disease. Though Price called this unidentified nutrient “activator X,” most experts now believe it was vitamin K.
Benefits of vitamin K and why it's important
The main role of vitamin K is to allow the blood to clot – but it also has other functions. Let’s take a closer look at some of the ways that vitamin K benefits the body.
Vitamin K may improve bone health
Vitamin K2 plays an important role in how our bodies metabolise calcium – which is the main mineral found in our bones and teeth – and helps to promote the calcification of bones. Studies have linked low levels of vitamin K with osteoporosis, which is a common condition that causes bones to become brittle and weak.
One study of 244 postmenopausal women found that participants who took vitamin K2 supplements showed a much slower decline in age-related bone mineral density than participants who didn’t. Studies in Japan have reported similar findings – although very high amounts of vitamin K2 were used in these studies. Seven of these studies found that vitamin K2 reduced spinal fractures by 60%, hip fractures by 77%, and non-spinal fractures by 81%.
Due to these findings, vitamin K supplements are officially used to treat osteoporosisa in Japan – although it should be noted that not all experts are convinced. Two extensive review studies found that the evidence to suggest vitamin K supplements can prevent and treat osteoporosis is inadequate.
While more research is needed to conclusively link vitamin K to osteoporosis, we do know that it plays a crucial role in bone metabolism, and can generally improve bone health.
Vitamin K may improve cognitive health
Recent research suggests that vitamin K may have important benefits for brain health – especially among older adults. Several studies show that increased levels of vitamin K1 in the blood are linked with improved memory and a sharper brain.
In this study of healthy adults over the age of 70, participants who had the highest blood levels of vitamin K1 performed best in verbal episodic memory tests. Episodic memory refers to how well you remember important parts of daily life.
Another study of more than 950 older adults found that those who consumed the highest amounts of vitamin K1 experienced slower cognitive decline. The study tracked both the diets and cognition of the participants for five years, and their findings showed that the adults who consumed greater amounts of dark green, leafy vegetables (which are very high in vitamin K) had the cognitive abilities of someone 11 years their junior.
Vitamin K may improve heart health
Vitamin K helps prevent mineralisation (which is when minerals like calcium build up in your arteries) and it’s believed to help keep blood pressure low – making it easier for the heart to pump blood around the body. Mineralisation occurs naturally as we get older, and it’s a serious risk factor for heart disease.
Because vitamin K is believed to prevent mineralisation, it’s also believed to protect against heart disease. One study that took place across seven to 10 years found that people who consumed high levels of vitamin K had a 57% lower risk of dying from heart disease. Another study of more than 16,000 women found that for every 10 mcg of vitamin K2 each participant consumed daily, their heart disease risk was lowered by 9%.
However, it’s important to note that these studies were only observational, and so cause and effect can’t be proven. Longer-term clinical trials on vitamin K and heart disease are needed before we can draw definitive conclusions. Though, due to vitamin K’s effectiveness in preventing mineralisation, it’s likely that it can help improve overall heart health.
You can read more about the link between heart health and vitamin K in our article; 10 delicious foods that can boost heart health.
Am I getting enough vitamin K?
According to the NHS, adults need approximately one microgram of vitamin K each day for every kilogram they weigh. So if someone weighs 70kg, for example, they’d need 70 micrograms of vitamin K each day.
Vitamin K is found naturally in many foods, so you should be able to get all you need from eating a varied, balanced diet. Vitamin K is also fat-soluble, and our bodies are able to store it for future use, which means we don’t need to eat it every day.
Because we should be able to get all the vitamin K we need from our diet, most people won’t need to take a supplement. However, some people who may not be able to get enough vitamin K include…
- Babies who didn’t receive a vitamin K injection at birth
- People with conditions like cystic fibrosis, coeliac disease, ulcerative colitis, and short bowel syndrome, which make it harder for their bodies to absorb vitamin K
- People who’ve had weight loss surgery
If you’re not sure whether you’re getting enough vitamin K, it’s important to speak with your GP before beginning to take any supplements. Vitamin K supplements can interfere with several types of medications, including blood-thinners, anticonvulsants, cholesterol-lowering drugs, and antibiotics.
There’s currently limited research on the effects of taking high doses of vitamin K daily. However, according to the NHS, taking 1mg or less of vitamin K supplements a day is unlikely to do any harm.
How can I get more vitamin K?
While several widely available foods are very high in vitamin K1, vitamin K2 is more elusive. However, the good news is that our bodies are able to partly convert vitamin K1 to K2. This is very handy when you consider that the amount of vitamin K1 in a normal diet is 10 times higher than that of vitamin K2! Our large intestines are also able to produce vitamin K2.
Vitamin K1 is mainly found in plant-based foods, particularly dark, leafy green vegetables. Vitamin K2 is only found in certain animal products and fermented plants, such as sauerkraut, miso, and natto (a Japanese product that’s made from fermented soya beans). Fermented foods are also really good for our gut and digestive health, so it’s always beneficial to eat more of them.
So which types of foods are the best food sources of vitamin K? Here are the top 10…
Kale (cooked) — 443% of your daily value (DV) per serving
Mustard greens (cooked) — 346% DV per serving
Swiss chard (raw) — 332% DV per serving
Collard greens (cooked) — 322% DV per serving
Natto — 261% DV per serving
Spinach (raw) — 121% DV per serving
Broccoli (cooked) — 92% DV per serving
Brussels sprouts (cooked) — 91% DV per serving
Beef liver — 60% DV per serving
Pork chops — 49% DV per serving
For more information on the different types of foods that contain vitamin K, check out this article from Healthline.
Final thoughts...
Vitamin K is a group of nutrients that are divided into vitamins K1 and K2. Vitamin K1 is involved in blood clotting and brain health, and vitamin K2 is believed to benefit bone and heart health.
While vitamin K deficiency is very rare, not getting enough may have detrimental effects on your health over time. For example, it may cause bleeding, weaken your bones, put your heart health at risk, and exacerbate age-related brain decline.
If you want to make sure that you’re getting enough vitamin K, the best way is to eat a healthy, balanced diet. For tips on this, head over to the diet and nutrition section of our website.
Do you feel like you have healthy levels of vitamin K – or do you have any additional tips for staying healthy? We’d be interested to hear from you in the comments below.