Wednesday, February 2, 2011

L-carnitine: The best supplement for weight loss?

Posted by Minhui Dai

Nowadays you can find lots commercials about weight loss anywhere. L-carnitine defeats other well-known supplements and is named as the fastest and safest way to lose weight. Firstly, L-carnitine transports long-chain acyl groups from fatty acids into the mitochondrial matrix, so they can be broken down through β-oxidation to acetyl-CoA to obtain usable energy via the citric acid cycle. That’s the way to metabolize fats and to prevent futile cycling between β-oxidation and fatty acid synthesis directly. Secondly, we can get L-carnitine from everyday food like red-meat, dairy and synthesized by our own healthy body. It is not a component that we made of but one that we original have. So L-carnitine is considered as the safest supplement.

In recent studies, L-carnitine is proved to have effect to protect the cell from oxidation damage which can be considered to use in antitumor medicine. Also L-carnitine treatment can reduce the neuronal loss and number of neuronal intranuclear aggregates. It is now used to prevent or treat Huntington’s disease.

More and more people get to know L-carnitine and are attracted by its intermediate effect in fatty biosynthesis and fat catabolism. But there is no evidence that carnitine supplements can improve weight loss performance in healthy individuals. Which I think does make sense. Here are some reasons I summarize from what I read and what I think.

The body can make enough carnitine to meet most people’s need. How many fats you burn considered the energy you use then how many carnitines will be produced. In recent animal experiments, it shows that L-carnitine consumption can influence the renal reabsorbtion of cartinition. Renal reabsorbtion is the way for kidney to retake useful components in initial urine. Some components’ reabsorbtion needs transporters, which can combine those components and be reclaimed by the body. L-carnitine is one of them. The number of its transporter called OCTN2 is limited. A study shows that treatment with L-carnitine affected neither the activity of carnitine transport into isolated renal brush border membrane vesicles, nor renal mRNA expression of the carnitine transporter OCTN2. In contrast, in carnitine deficient rats, carnitine transport into isolated brush border membrane vesicles was increased 1.9 fold compared to untreated control rats. So more extra carnitine you eat more you just urinate. And because of the decrease of transporters when you stop consuming this supplement the rate of fat catabolism will be lower than that before consumption. That’s why only carnitine deficient patients who suffer from peripheral vascular disease, cardiovascular, pulmonary, and kidney diseases and diabetes will take carnitine as medicine under doctor’s supervision.

On the other hand, some clinical cases show that carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a “fishy” body odor. And in some animal studies, carnitine persistently increases dopamine outflow in the nucleus accumbens. Dopamine dysregulation in this pathway has been shown to cause psychotic symptoms.

As the conclusion, in the theory, L-carnition is an efficient way to help lose weight. But it won’t and it causes some bad side effects. So do not believe those weight loss commercials. Eat healthier and exercise more!


  1. I think it is truly amazing how much time and money is spent on developing weight loss drugs. If losing weight was as easy as popping a pill, then certainly everyone would be skinny! But in a society that must have quick and easy solutions, two-thirds of America will remain overweight and the quest for the perfect weight loss drug will go on. With side effects such as the ones described above, it is a wonder anyone who even consider a weight loss supplement before substituting a salad for a Big Mac and taking the stairs instead of the elevator. Weight loss is something that almost anybody can achieve with with a little effort. Perhaps if drug companies spent less time developing and promoting an unreliable solution to a serious problem, people would realize they cannot rely on drugs for their every need.

    Posted by Brianna Lee

  2. I agree with you Brianna. As a student of food science major, I am confused that we need to make tasty food to encourage people to eat more but one the other hand we need to study weight loss drugs or components. If the food is less tasty or appear less attractive, people maybe eat less. But that will make food industry to loss costmers and food scientists lose their jobs.

    Posted by Minhui Dai

  3. The fact that people are willing to go through the terrible side effects to be thin is really discouraging. I know similar things occur with other weight loss drugs as well. People these days are so used to instant gratification because of technology that they are too lazy to go for a walk. People need to realize that if something sounds too good to be true then it usually is. Something promising weight loss with no diet changes or increased exercise are a scam and may cause further harm to their bodies.