New research suggests that vitamin K supplementation may help to slow the progression of insulin resistance, a condition that significantly increases an individual's risk of developing type 2 diabetes and heart disease.

Sarah Booth, director of the Vitamin K Laboratory at the Jean Mayer Human Nutrition Research Center on Aging at Tufts University, and colleagues analyzed data from the study of 355 non-diabetic men and women ages 60 to 80 to determine whether supplementation with 500 µg/day vitamin K (phylloquinone) – five times the Adequate Intake (AI) recommended by the Institute of Medicine's Food and Nutrition Board – would have any impact on insulin resistance.

Results showed that the vitamin K supplementation significantly slowed the progression of insulin resistance in men. Furthermore, men given the supplement also had lower blood insulin levels than men who received the placebo. However, vitamin K supplementation had no effect on women. The researchers believe that this may be due to the fact that there was a higher prevalence of obese or overweight women in the vitamin K supplementation group than there was in the male supplementation group. Vitamin K is stored in fat, and having excess fat may mean that vitamin K may not be as easily available to cells that need it.

The authors concluded that vitamin K supplementation “may reduce progression of insulin resistance in older men,” however they add that 500 µg/day is easily attainable by eating a healthy diet. Vitamin K rich foods include brussels sprouts, broccoli, and dark, leafy greens, such as kale and spinach.

Yoshida M, Jacques PF, Meigs JB, Saltzman E, Shea MK, Gundberg C, Dawson-Hughes B, Dallal G, Booth SL. Effect of Vitamin K Supplementation on Insulin Resistance in Older Men and Women. Diabetes Care 2008;31:2092-2096.

News release: Vitamin K linked to insulin resistance in older men. Tufts University, Health Sciences. November 26th 2008.