Carnitine Absorption Study in Vegetarians
A few months ago a study was published on carnitine absorption in the muscles of vegetarians. Here is what I added to VeganHealth.org’s Vegan Weightlifting: What Does the Science Say?, which is where most of my info on carnitine resides (italics added to the new sentences):
“Carnitine levels tend to be lower in people eating lower fat, higher carbohydrate diets. When intake of carnitine is low, less carnitine is excreted. Vegans and lacto-ovo vegetarians have lower blood levels of carnitine. Researchers in one study did not think the lower carnitine levels of vegetarians were unhealthy. It is not known if the lower levels have any bearing on athletic performance. A 2011 study showed vegetarians’ muscles to have a lower ability to absorb carnitine than omnivores. Vegetarians also excreted less carnitine than omnivores, indicating that other tissues or muscles that were not tested were possibly absorbing the carnitine.”
Some added thoughts:
This paper included two studies. In the first study, subjects were given both insulin and carnitine intravenously. The researchers thought the insulin would help enhance carnitine absorption. I would not rule out the possibility that the insulin might have confounded the study in terms of what normally would occur.
In the second study, subjects ate 3 g of carnitine in one dose and had their measurements taken about 24 hours later, only one time. This would give the body very little time to adapt to a larger carnitine intake.
Finally, it is still not clear that vegetarians’ lower levels of muscle carnitine have any physiological significance. I once supplemented with carnitine for a few days and experienced no noticeable health improvement (such as increased energy). But I do know of one person who did very poorly on a vegan diet until he started supplementing with carnitine.
Stephens FB, Marimuthu K, Cheng Y, Patel N, Constantin D, Simpson EJ, Greenhaff PL. Vegetarians have a reduced skeletal muscle carnitine transport capacity. Am J Clin Nutr. 2011 Sep;94(3):938-44. | Link