Vitamin K supplements may improve glucose metabolism, insulin sensitivity: Review

The review, published in Nutrition​ ​ and authored by Prasenjit Manna and Jatin Kalita from the CSIR-North East Institute of Science and Technology in India, concludes that naturally occurring Phylloquinone (K1) and Menaquinones (K2) are beneficial among people with metabolic syndrome and at a high risk of type 2 diabetes.

Manna and Kalita added that the benefits observed for phylloquinone were observed at significantly lower doses of menaquinones, suggesting that menaquinones may be more effective than phylloquinone in reducing the risk of type 2 diabetes.

“This review for the first time provides an overview of the currently available preclinical and clinical evidences about the beneficial role vitamin K supplementation on insulin sensitivity and glucose metabolism, which may be helpful for the development of a novel adjuvant therapy to achieve better control of glycemia and improve the lives of the diabetic patient population.” ​

K forms​

There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) which is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90% of the vitamin K in a typical Western diet; and menaquinones (vitamins K2), which make up about 10% of Western vitamin K consumption and can be synthesized in the gut by microflora.

Menaquinones (MK-n: with the n determined by the number of prenyl side chains) can also be found in the diet; MK-4 can be found in animal meat, MK-7, MK-8, and MK-9 are found in fermented food products like cheese, and natto is a rich source of MK-7.

“The awareness of Vitamin K2 and its benefits grows”​

Dr Hogne Vik, Chief Medical Officer of vitamin K2 supplier NattoPharma, told NutraIngredients-USA: “Manna and Kalita conclude that clinical trials show both vitamin K1 (phylloquinone) and vitamin K2 as MK-7 (menaquinone-7) are beneficial for patients with metabolic syndrome and high risk of type 2 diabetes (T2D), but note that the risk reductions were found for lower intake of K2 than K1, suggesting that vitamin K2 could be more effective. The authors also suggest that the vitamin K-dependent protein osteocalcin (OC) is important in the regulation of glucose metabolism. ​

“It's good to see that great work continues and that the awareness of Vitamin K2 and its benefits grows, yet more has to be done. This paper should be used to support future research programs to further confirm and explore the vitamin K effects for risk reductions for developing diseases, and also identifying diseases where vitamin K could be the preferred action over a drug. ​

“NattoPharma is aware of this application, yet we are pursuing our own research as well.”​

Mechanism ​

Commenting on the potential mechanism(s) of action for improving insulin sensitivity and glucose tolerance, the authors noted several possibilities including carboxylation of vitamin K-dependent protein, regulation of adipokine levels, anti-inflammatory activity, and lipid lowering effects.

“However, there is so far no mechanistic study describing in detail about the molecular mechanism underlying the beneficial role of vitamin K in insulin sensitivity and glucose metabolism,” ​they added. “Thus, future studies with diabetic animals and diabetic patients are needed to dissect the molecular mechanism underlying the beneficial function of vitamin K in improving insulin sensitivity and glucose metabolism in diabetic pathophysiology.”​

Source: Nutrition​​
Published online ahead of print, doi: 10.1016/j.nut.2016.01.011
“Beneficial role of vitamin K supplementation on insulin sensitivity, glucose metabolism, and the reduced risk of type 2 diabetes: A review”​
Authors: P. Manna, J. Kalita