In the study involving 355 non-diabetic men and women ages 60 to 80, researchers from Tufts University have found that vitamin K can slow insulin resistance in older men while increase in older women.
"Men who received vitamin K supplementation had less progression in their insulin resistance by the end of the clinical trial," said Sarah Booth, senior author and director of the Vitamin K Laboratory at the USDA HNRCA.
"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," she added.
During the research, both men and women took daily multivitamins containing 500 micrograms of vitamin K, five times the recommended Adequate Intake (AI) by the Institute of Medicine's Food and Nutrition Board, with instructions to maintain normal diets without any additional supplementation.
They also received a calcium and vitamin D supplement, while those in control group received no vitamin K supplementation, however, they were given multivitamin and the calcium and vitamin D supplement.
The researchers found that in addition to improved insulin resistance, the supplemented men had lower blood insulin levels compared to the unsupplemented men.
People who are obese or overweight are prone to insulin resistance because excess fat can interfere with insulin function. The authors believe that weight might explain why only the vitamin K supplemented men improved their insulin resistance.
"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 said.
"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," she added.
The study appears in the November issue of Diabetes Care.