Increased intakes of vitamin K may reduce the risk of developing type-2 diabetes, says a new study with almost 40,000 Dutch men and women.
For every increase of 10 micrograms of vitamin K2 intake the risk of type-2 diabetes was reduced by 7 percent, according to findings published in Diabetes Care.
Correlation does not prove causality however and more research is clearly needed to explore the potential benefits of a vitamin K-rich diet in reducing the risk of type-2 diabetes, a disease that affects almost 24 million Americans, equal to 8 percent of the population. The total costs are thought to be as much as $174 billion, with $116 billion being direct costs from medication, according to 2005-2007 American Diabetes Association figures.
Researchers from the University Medical Center Utrecht and the Dutch National Institute for Public Health and the Environment report that vitamin K1 intakes “tended to be associated with a reduced risk of type 2 diabetes”. This link was not statistically significant, however.
There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) and menaquinones (vitamins K2). K1 is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90 per cent of the vitamin K in a typical Western diet; while K2, which makes up about 10 per cent of Western vitamin K consumption and can be synthesised in the gut by microflora.
Led by Joline Beulens, the researchers analysed data from 38,094 Dutch people aged between 20 and 70. Food frequency questionnaires were used to evaluate dietary intakes of phylloquinone and menaquinones.
During 10.3 years of study, the researchers documented 918 people developed diabetes. After crunching the numbers, it was calculated that for each 10 microgram increase in menaquinone intake, the risk of developing type-2 diabetes by 7 per cent.
Previously, researchers from America, Canada and Britain reported in the journal Cell that vitamin K may have an effect on diabetes development via the vitamin K-dependant protein osteocalcin. The study with mice looked at genes that operate primarily in the bone cells that are linked to glucose metabolism.
By "knocking out" these genes in mice so that they could not function, the animals lacking a functional osteocalcin gene gained fat, showing that osteocalcin helps regulate the cells that produce insulin in the pancreas and release it into the bloodstream.
However, such a mechanism was dismissed by scientists from the Jean Mayer USDA Human Nutrition Research Center at Tufts University in 2008. Sarah Booth and co-workers noted that men in vitamin K group actually had less of the functional osteocalcin than men in the placebo group.
“It is plausible,” they stated in Diabetes Care (Vol. 31, pp. 2092-2096), “that vitamin K may improve insulin sensitivity through suppression of inflammation. In vivo and in vitro studies have shown that vitamin K reduced lipopolysaccharide-induced inflammation.
“More recently, it was reported that biochemical and dietary measures of vitamin K status were inversely associated with inflammatory markers in an observational study,” they said.
Source: Diabetes Care
Published online ahead of print, doi: 10.2337/dc09-2302
“Dietary phylloquinone and menaquinones intake and risk of type 2 diabetes”
Authors: J.W.J. Beulens, D.L. van der A, D.E. Grobbee, I. Sluijs, A.M.W. Spijkerman, Y.T. van der Schouw