Thursday Nov 26, 2008 (foodconsumer.org) -- A new study found that taking vitamin K supplements slowed the development of insulin resistance, a precursor to diabetes, in elderly men ages 60 to 80.

The three-year clinical trial of 355 men and women led by Sarah Booth at the Jean Mayer Human Nutrition Research Center on Aging at Tufts University (USDA HNRCA) did not show the same effect in women who received vitamin K supplements.

"Conversely, we saw progression in insulin resistance in women who received vitamin K supplementation, and in the men or women who were not given vitamin K supplements," Booth said.

In their report published in the November 2008 issue of Diabetes Care, the researchers speculated that body weight makes the difference.  

Insulin resistance is a condition in which the body cannot use insulin properly, causing glucose to build up in the blood. People who are obese or o verweight are more susceptible to insulin resistance because excess fat can interfere with insulin function.

"In our study, there was a higher prevalence of obese or overweight women in the vitamin K supplementation group compared to the male supplementation group," Booth explained. "Vitamin K is stored in fat tissue. If there is excess fat, vitamin K may not be readily available to cells that require it to process glucose."

In the trial, both men and women were assigned daily multivitamins containing 500 micrograms of vitamin K, a dose that was five times higher than the Adequate Intake (AI) recommended by the Institute of Medicine's Food and Nutrition Board.

The subjects were also given a calcium and vitamin D supplement. In the control group, men and women were assigned the same multivitamins and calcium and vitamin D except that they did not receive vitamin K.

The researchers said the dose of vitamin K or phylloquinone may be obtained through a healthy diet consisting of good sources of vitamin K including Brussels sprouts, broccoli, and dark, leafy greens, such as spinach and collards.