When most people talk about vitamin K, they usually mean vitamin K1 – a vitamin best known for its role in blood clotting. But there is more to vitamin K, which is a basically a group of essential fat-soluble vitamins which come in different forms, including vitamin K1 and vitamin K2.
Vitamin K2 is surrounded by many common misconceptions, which unfortunately make it easy to overlook how important this vitamin is for our absolute health and well-being.
Myth 1: Vitamins K1 and K2 have similar functions and health benefits.
The truth is your body treats both vitamins very differently (some experts even point out that vitamin K2 may be more effective than K1 in supporting blood clotting processes). Vitamin K1 reaches the liver where it is used to make proteins needed for blood coagulation. On the other hand, vitamin K2 reaches other tissues besides the liver, performing many more functions and delivering all kinds of health benefits.
Myth 2: You don’t need to worry about vitamin K2 intake as long as you are eating a lot of green leafy vegetables, as your body converts some of the vitamin K1 that you consume through food into K2.
This point, again, has no merit. Both vitamins come from very different sources. Your body can’t convert K1 into K2 as effectively to achieve optimum levels. Vitamin K1 (phylloquinone) is found in leafy green vegetables such as kale, spinach, mustard greens, broccoli and Brussel sprouts. K1 is also found in several fruits and grains. Vitamin K2 (menaquinone) is found in fermented foods, and in animal-based products.
Coming back to vitamin K2, over the past years, researchers have discovered important information about the vitamin and its potential role in a lot of common, widely prevalent health concerns – such as osteoporosis, heart disease (due to calcification in arteries), cancer, rheumatoid arthritis, cancer and cognition. 
Vitamin K2 highlights
- Vitamin K2 exists is many other forms ranging from MK4 to MK13. While M stands for menaquinone, the number indicates how many side-chains are attached to the molecule.
- MK4 is most abundant in animal-based foods such as meat, eggs and dairy (grass fed variety)
- MK7 is most abundant in fermented foods. Natto, a fermented soybean dish, is the richest source of MK7. Other sources are sauerkraut and cheese.
Signs of Vitamin K2 Deficiency
The fact is most people are deficient in vitamin K2. Sadly, the signs that you have low levels may be difficult to pin-point as K2 insufficiency doesn’t really cause obvious, painful symptoms; at least not immediately. But understanding the factors that make you deficient and conditions that may manifest due to poor levels (poor bone health, for example) may give you some insights on your vitamin K2 status.
Risk factors for vitamin K2 deficiency
- Diet lacking in vitamin K2: Most people don’t usually consume foods that are rich in vitamin K2.
- Excessive use of anticoagulants: Heart patients are often prescribed anticoagulant drugs like warfarin (Coumadin), which prevents the synthesis of vitamin K dependent proteins involved in blood clotting. That’s how warfarin works and causes the blood to clot more slowly.
- Prolonged, frequent use of antibiotics: Antibiotics destroy healthy bacteria in the gut that not only help in production of vitamin K2 but also play an important role in its absorption.
- Absorption issues: Gastrointestinal problems such as celiac disease, Crohn’s disease, ulcerative colitis, abdominal surgeries and gut dysbiosis (overgrowth of bad bacteria), can also contribute to deficiency. These issues interfere with healthy absorption of vitamin K2 (and other nutrients you need for vibrant health).
- Liver dysfunction: Any kind of liver disease, such as cirrhosis, interferes with the synthesis of vitamin K-dependent factors.
- Use of statins: Studies have shown that statins, cholesterol lowering drugs, inhibit the absorption of vitamin K2. It is because statins basically work by inhibiting an enzyme that helps your liver to make cholesterol. This enzyme, however, sits at the base of a huge chain of bio-chemical reactions that also produce many other compounds such as vitamin D, CoQ10, stress hormones, bile acid and of course, vitamin K2.
- Low fat diet: Since K2 is a fat-soluble vitamin, people on a low-fat diet have issues absorbing the vitamin.
Health conditions associated with vitamin K2 deficiency
Osteoporosis and increased risk of fractures
The combination of calcium and vitamin D alone is not enough to ward off osteoporosis, if you don’t have sufficient vitamin K2 levels in your body. In fact, vitamin D (which helps in calcium absorption) works in perfect partnership with K2 (which moves calcium into the places where it belongs and out of the areas where you don’t need it).
The health risks associated with calcium intake (heart attack, stroke, kidney stones, muscle spasms, constipation etc.) arise not because of calcium itself but when you don’t maintain a healthy balance between other nutrients such as magnesium, D3 and K2. These nutrients work with each other to help the body absorb and use calcium in the most efficient manner … otherwise calcium builds up in unwanted places.
Studies show that a combination of calcium-K2-D3 helps improve bone strength and reduces risk of fractures. In fact, Vitamin K2 is a recommended treatment for osteoporosis in Japan. Studies even show that vitamin K2 helps lower bone loss in postmenstrual women. This study showed that vitamin K2 supplementation improved bone mineral content, bone mineral density and bone strength in healthy post-menstrual women without osteoporosis. 
How does vitamin K2 influence bone health?
Vitamin K2 activates osteocalcin, a protein produced by bone-forming cells called osteoblasts. Osteocalcin attaches to the calcium circulating in the bloodstream and sends it to the bone matrix, where it helps in building healthy, strong bones.
Poor heart health and increased risk of heart attack and stroke
Low levels of vitamin K2 have a surprising effect on your heart health too. It is because K2 activates Matrix GLa protein (MGP), a protein that attaches to the calcium and prevents it from getting into the soft tissues such as blood vessels and cartilage. MGP is known as one of the most powerful inhibitors of calcification of arteries, a very strong and independent risk factor for coronary heart disease.
Vitamin K2 deficiency impairs the function of MGP, which leads to abnormal, excessive accumulation of calcium in the arteries (and other soft tissues). The well-known Rotterdam study and many other studies have found that increasing the intake of vitamin K2 lowers the risk of arterial calcification and death from heart disease.  
Several studies show that K2 exerts anti-cancer effects on various cancer cell lines through multiple mechanisms. Vitamin K2 is believed to have these anticarcinogenic effects because of its ability to regulate expression of genes. It has been shown to:
- Induce apoptosis (cell death) and degradation in leukaemia cells 
- Lower risk of advanced prostate cancer (whereas higher intake of vitamin K1 was not associated with this benefit). 
- Supress the recurrence of liver cancer 
Type 2 Diabetes
Both observational studies and clinical trials have shown that vitamin K2 reduces the risk of Type 2 diabetes. A recent 2018 review of existing studies suggested that Vitamin K2 improved insulin sensitivity through multiple mechanisms that includes osteocalcin metabolism (osteocalcin works as an endocrine hormone to improve insulin sensitivity), lipid lowering effects and anti-inflammatory properties. 
Vitamin K2 supplementation (in the form of MK7) has been found effective in the treatment of rheumatoid arthritis, a disabling chronic inflammatory condition of the joints.
MK4 has already been found to reduce disease activity in RA patients. Following this, another study showed that MK7, with greater bioavailability than MK4, also showed immense benefit in RA treatment. The study found that MK7 decreased the levels of clinical and biochemical markers of inflammation like ESR, C-reactive protein and matrix metalloproteinase (MMP-3). 
In addition, MK7 also increased the level of osteocalcin, a protein that needs vitamin K2 to do its job. Osteocalcin, as we know, improves bone health by integrating calcium into bone matrix.
Even if you are eating a healthy diet, chances are you may still be deficient in vitamin K2 if you are not consuming fermented foods and animal-based foods. Natto is the richest source of vitamin K2, providing an astonishing 250 mcg per ounce. While this fermented soy product is quite popular in eastern Japan, it’s strong smell and flavour makes it less favored in other parts of the world. Egg yolk, beef, goose liver patty, and cheese are also good sources of vitamin K2.
While some of these vitamin K2 foods may be difficult and even expensive to source, you can also take a high-quality vitamin K2 supplement to improve your levels. The good news is that there is no known toxicity associated with high doses of vitamin K2. However, we always maintain that you must first consult your doctor before you start taking any new supplement.
- Gerry Kurt Schwalfenberg. Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health. J Nutr Metab. 2017.
- Knapen et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013
- Johanna M. Geleijnse et al. Dietary Intake of Menaquinone Is Associated with a Reduced Risk of Coronary Heart Disease: The Rotterdam Study. The Journal of Nutrition. 2004.
- G.C. Gast et al. A High Menaquinone Intake Reduces the Incidence of Coronary Heart Disease. Nutr. Metab. Cardiovasc. Dis. 2009.
- Yokoyama et al. Vitamin K2 induces autophagy and apoptosis simultaneously in leukemia cells. Autophagy. 2008
- Nimptsch et al. Dietary intake of vitamin K and risk of prostate cancer in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg). Am J Clin Nutr. 2008
- Ishizuka et al. Effect of menatetrenone, a vitamin k2 analog, on recurrence of hepatocellular carcinoma after surgical resection: a prospective randomized controlled trial. Anticancer Res. 2012
- MS Abdel-Rahman et al. Menaquinone-7 as a novel pharmacological therapy in the treatment of rheumatoid arthritis: A clinical study. Eur J Pharmacol. 2015
- Yan Li et al. Effect of vitamin K2 on type 2 diabetes mellitus: A review. Diabetes Research and Clinical Practice. 2018.