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Vitamin K2 – a form of vitamin K produced in the gut – plays important roles in blood clotting, bone mass maintenance, and blood vessel contractility. But new research shows that supplemental vitamin K2 also improves diabetes markers. People with type 2 diabetes who took supplemental vitamin K2 had better markers of glycemic control than those who took a placebo.

Researchers performed a three-part study in humans and mice. First, they conducted a randomized controlled trial involving 60 adults who had type 2 diabetes. Half of the participants took vitamin K2 every day for six months, while the other half took a placebo. Then the researchers transplanted gut microbes from vitamin K2-supplemented mice into obese mice. Finally, they analyzed the gut microbial composition and their metabolites in both humans and mice.

They found that the participants who received supplemental vitamin K2 experienced marked reductions in levels of fasting blood glucose (13.4 percent), insulin (28.3 percent), and HbA1c (7.4 percent), indicating improved glycemic control. Similarly, the mice demonstrated improved glucose tolerance after receiving the gut microbe transplants. Lastly, the researchers found that certain metabolites that play roles in glucose metabolism, including bile acids and short-chain fatty acids, increased in the feces of both groups. Furthermore, they identified a specific type of bacteria that was responsible for producing these metabolites.

Vitamin K is a fat-soluble vitamin. The body has limited vitamin K storage capacity, so the body recycles it in a vitamin K redox cycle and reuses it multiple times. Naturally occurring forms of vitamin K include phylloquinone (vitamin K1) and a family of molecules called menaquinones (vitamin K2). Vitamin K1 is synthesized by plants and is the major form found in the diet. Vitamin K2 molecules are synthesized by the gut microbiota and found in fermented foods and some animal products (especially liver).

These findings suggest that vitamin K2 participates in maintaining glycemic control in people with type 2 diabetes. They also underscore the role of the gut microbiota in this process. Learn about other roles for the gut microbiota in this episode featuring Dr. Eran Elinav.

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