Vitamin K May Have Anti-Diabetes Benefits
New research shows that supplements of vitamin K1 may reduce the development of insulin resistance in older men, thereby offering protection against diabetes.
Insulin resistance, whereby insufficient insulin is released to produce a normal glucose response from fat, muscle and liver cells, was significantly lower in men following a daily vitamin K1 supplement, according to results of a 36-month, randomized, double-blind, controlled trial.
No effects were observed in women, report the researchers, led by Sarah Booth from the Jean Mayer USDA Human Nutrition Research Center at Tufts University.
The authors speculated that weight might be influencing the effects of vitamin K in men and women. “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,” said Booth. “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.”
There are two main forms of vitamin K: phylloquinone, also known as phytonadione (vitamin K1) and menaquinones (vitamin K2). K1 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; while K2, which makes up about 10% of western vitamin K consumption, can be synthesized in the gut by microflora.
The researchers recruited 355 non-diabetic men and women between the ages of 60 and 80. Sixty percent of the participants were women. The participants were randomly assigned to receive a daily vitamin K1 supplement (500 mcg per day of phylloquinone) or placebo for 36 months. The vitamin K dose is approximately five times the adequate intake, said the researchers. All of the participants also received a calcium and vitamin D supplement.
Booth and her co-workers report that insulin resistance, assessed using the homeostasis model, improved in men consuming the vitamin K supplements. On the other hand, progression of insulin resistance continued in all women, and in the men in the placebo group.
The researchers concluded: “Vitamin K supplementation for 36 months at doses attainable in the diet may reduce progression of insulin resistance in older men.”
Diabetes Care 31:2092-2096, 2008
