Never heard of vitamin K, much less K2? You’re not alone. Other vitamins receive significantly more attention than the humble vitamin K2. So, what is it? And why should you care?
What is Vitamin K?
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Vitamin K is a potent nutrient that’s vital for health. It wasn’t discovered until 1929, when it was found to be essential for blood clotting (or coagulation). It was originally called “Koagulationsvitamin” when reported in a German research journal, which is where the K comes from. 1 This vitamin was also found to play an important role in calcium metabolism and heart health.
Later, a dentist by the name of Weston Price found that specific diets (i.e., those found in non-industrialized areas) appeared to better protect against tooth decay and other diseases. He believed that a nutrient was missing from those in industrialized nations and called that nutrient “activator X.” Now, it’s thought the missing nutrient may have been vitamin K2. 1
Vitamin K1 vs Vitamin K2
There are two main forms of this vitamin with different chemical structures and side chains. Vitamin K1 (phylloquinone) is found in leafy greens and other plant foods. Vitamin K2 (menaquinone), on the other hand, is found in animal foods and some fermented foods. 2
The body uses both types of vitamin K to produce a compound called prothrombin. This protein is vital for blood clotting, heart health, and bone metabolism. In addition, vitamin K is needed for energy production within the cells’ mitochondria and acts as an antioxidant to protect cells from free radical damage.
There is debate on how important and how different vitamin K1 and vitamin K2 are. So, more research is needed to fully understand how each one impacts human health. 3
Benefits of Vitamin K2
While more research is needed, several studies have shown how positive and necessary vitamin K2 is for our health. For instance, vitamin K2 may:
1. Support Heart Health
Vitamin K2 appears to help prevent calcium from being deposited and building up in the arteries. 4 This build-up is a big risk factor when it comes to heart disease.
One long-term study, for instance, found that people who consumed the most vitamin K2 through their diets were up to 52% less likely to see artery calcification. This led to a 57% lower risk of heart disease death. 5
Another larger study with 16,057 individuals found that for every 10 mcg of vitamin K2 consumed through foods, the risk of heart disease was reduced by up to 9%.6 More research is needed. Still, the nutrient vitamin K2 shows promise for protecting the heart.
2. Promote Bone Health
As we get older, bones can weaken (a condition known as osteoporosis) and increase the risk of fractures when we fall. Because vitamin K2 is important for calcium metabolism—it appears to activate calcium-binding proteins like matrix GLA protein and osteocalcin—it’s an important nutrient for bone health. 7,8
One three-year study with postmenopausal women found that supplementing with vitamin K2 led to a slower decline in bone mineral density as they aged. 9 Several long-term studies from Japan have shown positive improvements in bone health with added vitamin K2. For instance, it was found that spinal fractures, hip fractures, and other fractures were reduced by 60%, 77%, and 81%, respectively. 10 No wonder vitamin K2 supplements are included in the recommendations for supporting bone health in Japan. 11
Again, however, more research is needed and not all scientists agree that supplementation with vitamin K is necessary or even recommended. 12
3. Support Stronger Teeth
One of the first benefits of vitamin K2 noted by researchers is its effects on dental health. Results from animal studies (no human studies have been performed) have found that osteocalcin is needed to stimulate new dentin. Dentin is the calcified tissue found beneath the outer layer of enamel. And vitamin K2 is needed to activate osteocalcin. Combined with vitamin D, vitamin K2 may be one of the most important nutrients for strong, healthy teeth. 13 – 15
4. Help Protect Against Disease
Diseases like cancer are some of the most common causes of death in America. The best way to treat them is to prevent them from happening if possible. According to some studies, getting more vitamin K in your diet may help you stave off some diseases or increase survival times, including from liver and prostate cancer. 16 – 18 Again, however, only a couple of studies have come to this conclusion. So, more research is needed to know how effective vitamin K2 is for helping protect against diseases.
Other potential benefits of vitamin K2 include helping decrease inflammation in people with rheumatoid arthritis, improving hormonal balance, promoting kidney health, and supporting insulin sensitivity. 19 – 21
Deficiency Symptoms of Vitamin K
While many of us may not be getting optimal amounts of vitamin K, few Western adults experience actual deficiencies. Those most at risk include people with gastrointestinal disorders like celiac or ulcerative colitis. It can also include people suffering from malnutrition due to excessive dieting, lack of access to healthy foods, alcohol use disorder, and prolonged illness with vomiting or diarrhea.
Deficiency symptoms can include:
- Slower blood clotting and a higher risk of hemorrhage
- Increased bruising and bleeding
- Reduced bone mineralization, which can increase the risk of osteoporosis
- High blood pressure, arterial calcification, and other heart-related issues
- Increased risk of tooth decay and cavities
- Poor blood sugar management
- Metabolic issues
A deficiency may also result after the use of medications, especially a long course of antibiotics, which could throw off the balance of the gut microbiome, so it produces less vitamin K. Other medications that could negatively affect the absorption of vitamin K or dangerously interact with medications include cholesterol-lowering medications and blood thinners. For example, vitamin K may interact with blood thinners like Coumadin and increase the risk of heart problems. As always, if using any medications, it’s best to talk with your doctor before changing your diet or supplementation to avoid complications or dangerous interactions.\
Because vitamin K2 is fat soluble, there are also risks of obtaining too much. However, those risks appear to be fairly low as researchers have found that getting up to 15 mg (rather than the recommended mcg levels) 3 times daily is generally safe.
Vitamin K2 Foods to Add to Your Diet
With such promising potential benefits, many of us want to increase our consumption of vitamin K2. While many foods are rich in vitamin K1, vitamin K2 is harder to find. That said, it is possible for the body to partly convert K1 to K2, although the process isn’t all that efficient. Finally, small amounts of vitamin K2 are created in the gut by good bacteria.
Foods that provide vitamin K2 include: 22 – 23
- Natto
- Liver and other organ meats, including liver pate
- High-fat dairy products (especially from grass-fed cows), including hard, soft, and blue cheeses, whole milk, cream, and butter
- Egg yolks (from pasture-raised chickens)
- Pork, including chops, bacon, and cured ham or Canadian bacon
- Dark meat chicken
- Turkey sausage
- Sauerkraut
- Miso
- Beef
- Duck
- Fatty fish, such as salmon
- Cooked soybeans
- Sprouted and cooked mung beans
- Cashews
- Red kidney beans
- Hazelnuts
- Pine nuts
- Pecans
- Walnuts
Of course, we do need both types of vitamin K. Foods that contain higher amounts of vitamin K1, which the body may also use to convert to vitamin K2, include:
- Kale
- Mustard greens
- Swiss chard
- Collard greens
- Beet greens
- Raw spinach
- Dandelion greens
- Broccoli
- Brussels sprouts
- Green beans
- Prunes
- Kiwi
- Avocado
- Cooked green peas
- Fresh parsley
- Cooked cabbage
- Arugula
- Lettuce
Though fruits contain smaller amounts of vitamin K than vegetables, a few that do provide a reasonable amount include:
- Blackberries
- Blueberries
- Pomegranates
- Dried figs
- Sundried tomatoes
- Grapes
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Because vitamin K is a fat-soluble vitamin, to help your body absorb the vitamin K found in foods, it’s best to eat them with fats or in high-fat foods like bacon, butter, or oil.
Because foods rich in vitamin K2 aren’t all that common in many people’s diets, you may want to look at a supplement to help ensure you’re getting enough. You can often find quality vitamin D supplements that also contain vitamin K2, especially the MK-4 or MK-7 forms, because D and K vitamins work synergistically together to support health.
Vitamin K2 Wrap-Up
While few people have even heard of vitamin K2, promising research indicates this nutrient is vital for health, especially heart and bone health. Whether you get it through foods or supplements, getting enough vitamin K (120 mcg is the Recommended Daily Value for men and 90 mcg for women, and some experts recommend increasing that amount to 150 to 400 mcg per day, depending on current health levels) does a body good.
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