Vitamin K was discovered in 1935. However, not many of us know that it is not a single vitamin, but a family of fat-soluble vitamins. The two primary forms of vitamin K are vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). In this article, we will learn about vitamin K2, its functions, and how it plays an essential part in our health.
What is vitamin K2?
Vitamin K is a family of fat-soluble vitamins. It comes in two primary forms –
Vitamin K1 (phylloquinone) – Green leafy vegetables like collard greens, spinach, and kale contain vitamin K1.
Vitamin K2 (menaquinone) – It is present in organ meats and fermented foods. Our gut bacteria also produce vitamin K2.
Vitamin K was discovered by Danish Scientist Henrik Dam in 1935. He initially called it the Koagulations vitamin due to its ability to help in blood clotting.
Vitamin K activates proteins that help in blood clotting, calcium metabolism, and heart health. It promotes calcification of bones and prevents calcification of blood vessels and kidneys (1). Vitamin K also helps the energy production of the mitochondria of cells.
While vitamin K1 is involved in the coagulation of blood, vitamin K2 plays many more functions in the body. During a 12-year study that involved 36,629 participants, researchers found that high vitamin K2 intakes can reduce the risk of peripheral artery disease. This association is stronger in hypertensive participants. Vitamin K1 intake, on the other hand, is not associated with peripheral artery disease (2).
Health benefits of vitamin K2
1. Lowers the risk of heart disease
Vitamin K2 reduces the risk of heart damage due to heart disease and improves overall heart health. Calcium build-up in arteries can lead to heart disease. Vitamin K2 can reduce the build-up of calcium in the blood vessels.
According to a 2015 study, vitamin K2 inhibits arterial calcification and arterial stiffening. Vitamin K2 prevents the build-up of calcium by activating the protein, which inhibits the deposition of calcium on the wall of the blood vessels. Increasing your intake of dietary calcium can help solve this problem (3). Another study suggests that dietary intake of vitamin K2 can reduce the risk of artery calcification by 52% (4).
A study from the University Medical Centre Utrecht, The Netherlands, found that the risk of coronary heart disease reduced by 9 percent for every ten mcg of vitamin K2 consumed per day (5).
2. Improves bone health
Vitamin K2 also plays a crucial role in bone health. It promotes healthy bone mineral density by synthesizing osteocalcin, an essential protein that binds calcium to bones. Vitamin K2 has been approved for the treatment of osteoporosis in Japan since 1995 (6).
During one study, 244 healthy postmenopausal women received 180 μg MK-7 capsules (vitamin K2 supplements) or a placebo for three years. The results showed that MK-7 intake significantly improved vitamin K status and decreased the age-related decline in bone mineral density (7).
During a systematic review of 13 studies, researchers observed that vitamin K2 supplements, when taken over six months, can help reduce bone loss. Only one trial did not show an improvement.
Seven of these trials studied the effect of vitamin K2 on fractures and observed that vitamin K2 helps reduce spinal fractures by 60%, hip fractures by 77%, and non-spinal fractures by 81% (8).
3. Reduces anxiety and depression
Elevated glucose levels can lead to depression, anxiety, and memory deficit. Studies have shown that vitamin K2 can improve anxiety and depression. During a study by the Medical University of Verna, Bulgaria, researchers examined the effect of vitamin K2 on rats with metabolic syndrome. After the 10-week study, the researchers observed that vitamin K2 normalized blood glucose, reduced anxiety, and depression, but did not improve memory in the rats (9).
Though this study shows that vitamin K2 can be beneficial in reducing anxiety and depression, we need more research to study its effects on human subjects.
Vitamin K2 is a crucial nutrient for oral and dental health. It keeps the oral microbiome in balance, prevents cavities, and supports remineralization. Researchers believe vitamin K2 is beneficial because of the proteins that it activates. K2 dependent matrix GLA protein (MGP) finds calcium in soft tissues, and osteocalcin directs it to teeth and bones.
Osteocalcin helps to trigger the growth of new dentin, which is the calcified tissue that is under the enamel of the teeth (10).
5. Helps fight cancer
Vitamin K2 possesses antioxidant properties that may help fight cancer. Some research also suggests that vitamin K2 can help suppress genetic processes that lead to tumor growth. During a lab-based study, scientists modified vitamin K2 with a ligand conjugate sialic acid–cholesterol, and this helped to suppress tumor growth in mouse cells (11).
According to a study from Saga Medical School, Japan showed that menatetrenone, a vitamin K2 analog, has a suppressive effect on the reoccurrence of hepatocellular carcinoma (12). Another study from the German Cancer Research Centre, Heidelberg, found that high vitamin K2 intake can reduce the risk of advanced prostate cancer by 63%. Vitamin K1 does not affect prostate cancer (13).
6. Reduces the risk of diabetes
Type 2 diabetes mellitus is a major public health problem around the world. Research has shown that vitamin K2 supplementation can reduce the risk of type 2 diabetes mellitus. According to a review of several studies, vitamin K2 improves insulin sensitivity through the involvement of vitamin K dependent protein osteocalcin, anti-inflammatory properties, and lipid-lowering effects (14).
Vitamin K2 has a better effect on type 2 diabetes than vitamin K1. During one study, when vitamin K2 was given to rats with metabolic syndrome, it normalized their blood glucose levels and reduced anxiety and depression (15).
Studies have also shown that a higher intake of vitamin K2 and not vitamin K1 is associated with a lower incidence of metabolic syndrome. Metabolic Syndrome is a cluster of metabolic abnormalities and is associated with an increased risk of diabetes and cardiovascular diseases (16).
The recommended intake of vitamin K2
The recommended daily intake of vitamin K for adults 19 years and older is 120 mcg for men and 90 mcg for women. There is no specific recommended dose for vitamin K2 separately.
Foods high in vitamin K2
The foods rich in vitamin K2 include –
- Organ meats
- Egg yolks
- Dark chicken meat
The butter that comes from the milk of grass-fed cows has higher vitamin K2 content.
Why are we deficient in vitamin K2?
Vitamin K2 can not be stored in the body for as long as some of the other fat-soluble vitamins like vitamins A, D, and E. So, if you do not eat foods that contain vitamin K2, you are more likely to be deficient. Earlier, the nutritionists used to believe that vitamin K2 deficiency was rare. They believed that our diet provided us with enough vitamin K2, and our gut microbiome produced the rest. This belief has changed now.
The diet of Americans has changed. We no longer eat food rich in vitamin K2 like sauerkraut and organ meats. Studies also show that we eat much less vitamin K than what we ate 50 years ago.
Vitamin K2 is also produced by gut bacteria. The use of antibiotics can affect the gut microflora. Some studies have also shown that the use of broad-spectrum antibiotics can also lead to vitamin K2 deficiency (17). This can be dangerous for our bones and heart. Vitamin K2 deficiency is linked to calcium build-up in the arteries and osteoporosis. Some non-dietary factors that may worsen vitamin K2 deficiency include –
- Long term use of antibiotics
- Use of Dilantin during pregnancy
- Low-fat diet
- Fat blocking pills like Alli
- Cholesterol-lowering drugs like bile acid sequestrants
- Mineral oil
- Food preservative BHT
- GI tract diseases
- Liver diseases
- Estrogen drugs
Vitamin K2 supplements
You can prevent vitamin K2 deficiency by taking foods rich in vitamin K2. Vitamin K2 supplements are also a good option. Many multivitamin supplements contain both vitamin K1 and vitamin K2. Vitamin K2 is available either as MK-4 or MK-7 in the supplements.
The concentration of vitamin K1 and vitamin K2 can vary in different supplements. You should always read the nutrition labels carefully before you take the supplements. You can have additional benefits of vitamin K2 when you take it along with vitamin D. These two vitamins have synergistic effects and provide cardiovascular and skeletal benefits (15). Vitamin K2 supplements are safe, and there have been no reported side effects, even at high doses.
Vitamin K2 is a form of the fat-soluble vitamin K that is found in organ meats and fermented foods. This vitamin is necessary for the activation of osteocalcin, a protein that transports and integrates calcium into the bone to ensure healthy bones. It helps to reduce the risk of heart disease, improve dental health, fight cancer, and lower anxiety and depression.
Vitamin K2 deficiency is increasing in western countries. By increasing the intake of vitamin K2 foods, we can lower healthcare spending on osteoporosis and cardiovascular health.