Vitamin K2 Simply Explained

1. What Is Vitamin K2?

Vitamin K2 is a group of fat-soluble compounds from the vitamin K family. These compounds are called menaquinones. They occur in fermented foods and in animal products. Bacteria in the body can also form them. Vitamin K2 is often taken as a dietary supplement, also together with vitamin D.

2. Where Is It Found, and What Is It Made From?

Vitamin K2 is found in fermented foods such as natto and cheese. It is also contained in animal foods such as liver and egg yolk. Part of the vitamin K2 in the body comes from bacteria in the intestine. For dietary supplements, it is produced artificially or obtained by fermentation.

3. What Does Vitamin K2 Do? What Research Shows

Bone Density and Bone Metabolism

In postmenopausal women with bone loss, vitamin K2 improved bone density in several studies. Laboratory values for bone metabolism also changed favorably. In healthy women, bone strength was better preserved with vitamin K2 than without. Not all studies found a difference, and whether this prevents fractures is open 124811171922232941424345.

Bone Fractures

For bone fractures, one form of vitamin K2 (menaquinone-4) showed fewer new fractures than no treatment in one study 11. Another study with vitamin K2 without specifying the exact form found fewer vertebral fractures 17. In people with Alzheimer's and other diseases of the nervous system, fewer fractures occurred with menaquinone-4 612. Two reviews in postmenopausal women found no confirmed difference overall 23.

Arterial Calcification

In dialysis patients, menaquinone-7 improved a laboratory value for vitamin K deficiency 2535. However, vascular calcification mostly progressed just as it did without treatment 1825293540. Only one study in coronary heart disease found a slower increase in calcium in the coronary arteries 16. Mixtures with vitamin D or other substances do not allow a statement about vitamin K2 alone 7913. Even as an add-on to a basic treatment that both groups received, vitamin K2 did not change calcification 2032.

Arterial Stiffness and Blood Pressure

In healthy postmenopausal women, menaquinone-7 lowered vascular stiffness in one study. In kidney transplant recipients and dialysis patients, vascular stiffness increased less with vitamin K2 than without. Other studies found no difference. The studies are small and the results uncertain 101824262835363844.

Cardiovascular Events

Cardiovascular events have so far been recorded only as safety values. In two dialysis studies, they did not differ between the groups. Risk values for the heart and circulation also mostly remained unchanged. The studies are small and short, so the informative value is unclear 7182021303439.

Chronic Kidney Disease

In kidney and dialysis patients, mainly vascular, bone and coagulation values were measured. Studies on the course of kidney disease itself are still pending. A review reports a decrease in a deficiency laboratory marker with vitamin K2 49. In children with kidney disease, the deficiency values were higher than in healthy children 4748. A single case report with many simultaneous treatments does not allow a statement about vitamin K2 46.

Other Investigations

In type 2 diabetes, menaquinone-7 lowered fasting blood glucose and long-term blood glucose value more than a sham treatment 3133. In women with polycystic ovary syndrome, it improved insulin values and triglycerides 27. Menaquinone-4 lowered cholesterol in overweight young adults 36. Nocturnal leg cramps in older people were less frequent with menaquinone-7 than with a sham treatment 15.

4. How Was Vitamin K2 Taken in the Studies?

In the studies, vitamin K2 was mostly taken as a capsule or tablet. Menaquinone-7 and menaquinone-4 were tested most frequently. Some studies gave menaquinone-7 only together with vitamin D. Then the result cannot be attributed to vitamin K2 alone. The forms and amounts tested were different. Results for menaquinone-4 do not automatically apply to menaquinone-7.

5. Is Vitamin K2 Safe? Side Effects in the Studies

The studies report predominantly good tolerability of menaquinone-4 and menaquinone-7 213742. Severe side effects did not occur. Individual studies mention gastrointestinal complaints. In a dialysis study, participants discontinued mainly because of gastrointestinal complaints that were related to the unpleasant odor of the tablets 14. A review found more side effects with vitamin K2, but none severe 1. Two other reviews found no confirmed difference 23.

All details with tables and sources: full expert page on Vitamin K2