L-Carnitine is an amino acid that is naturally produced in the body and plays a vital role in the metabolism of fat. It functions as a transporter of fatty acids into the mitochondria. L-carnitine helps the body produce energy. Premature infants and some adults cannot make L-carnitine in sufficient amounts, which necessitates supplementation. L-carnitine is effective in treating and preventing L-carnitine deficiency and increasing red blood cell count in people with serious kidney disease. L-carnitine is only found in animal food sources such as meat, poultry, and dairy products. Human breast milk is an important source of L-carnitine for infants.
Researchers from the University of Stirling in Scotland investigated L-carnitine (LC) supplementation and its effect on blood glucose levels. The study recruited 8 lean male participants and 8 overweight/obese male participants and were administered either 3 grams of L-carnitine or 3 grams of glucose per day with their meals for 14 days. Participants then were required to undergo an oral glucose tolerance test (OGTT) which meant ingesting 75 grams of glucose and then measuring the effects. The L-carnitine group of lean men experienced significantly lower blood sugar levels than the placebo group of lean men. On the other hand, the L-carnitine group of overweight/obese men experienced higher blood sugar levels than the placebo group of overweight/obese men. The authors stated “The glucose handling/disposal response to oral LC is different between lean and overweight/obese suggesting that further investigation is required. LC effects on gastric emptying and/or direct ‘insulin-like’ actions on tissues should be examined in larger samples of overweight/obese and lean participants, respectively.”1
1 Galloway SD, Craig TP, Cleland SJ. Effects of oral L: -carnitine supplementation on insulin sensitivity indices in response to glucose feeding in lean and overweight/obese males. Amino Acids. Jul2011;41(2):507-15.