Adding the nutrient carnitine to the diet of obese rats helped the rats clear the excess sugar which had been accumulating in their blood. Carnitine also improved the rats' overall fuel burning ability (both sugar and fat). These results hint that oral carnitine supplements may be helpful to people who have elevated blood sugar, including those with type 2 diabetes.
Generally, the body produces sufficient carnitine so that dietary supplementation is not necessary. But as people age, their cells contain less carnitine.
Carnitine is a nutrient essential for proper fat metabolism. It binds to long−chain fatty acids and shuttles them into mitochondria, the cell's powerhouses. There, the fatty acids are burned (oxidized), producing energy. Carnitine also shuttles excess undigested and partially digested fatty acids out of the mitochondria and into the bloodstream, where they can be redistributed to the tissues that need them the most. This is usually the muscles, which require tremendous amount of energy.
Generally, the body produces sufficient carnitine so that dietary supplementation is not necessary. But as people age, their cells contain less carnitine. The best dietary source of carnitine is red meat.
The rats in the Duke study were fed a lifelong high−fat diet. This caused excess sugar to accumulate in their blood and led to several other abnormalities in their energy metabolism. One of these abnormalities was a lack of free carnitine, particularly in the muscles. All the compounds carnitine was shuttling back and forth were not being used by the body and remained stuck to carnitine, tying it up. Adding carnitine to the rats' diet for eight weeks reversed these abnormalities and restored the rats' fuel−burning ability.
In a 1999 human study of 20 normal subjects and 15 subjects with type 2 diabetes, intravenous carnitine helped the diabetics both remove the excess sugar from their blood and utilize it as fuel. That study used carnitine directly injected into the blood and only monitored the subjects for two hours. The 2009 study suggests that oral carnitine may also work.
The Duke team is scheduled to soon begin a small clinical trial of oral carnitine supplementation on those who are most likely to benefit from it—people aged 60 to 80 with reduced glucose tolerance.
An article detailing the Duke study was published in the August 21, 2009 issue of the Journal of Biological Chemistry.