Carnitines: Dissimilar Members of the Same Family
One of the best known amino acid is actually not an amino acid. L-Carnitine (also known as carnitine) is not an amino acid in the strict definition as it is not a component of proteins and more closely resembles a B-vitamin. Many readers are familiar with the general benefits of carnitine, such as its effect on improving cardiovascular health. The main biological effect of carnitine is to shuttle long chain fatty acids into the mitochondria, which is the energy manufacturing organelle inside our cells. Systemically, the overwhelming amount of carnitine (approximately 95%) is found in our skeletal muscle and heart tissue cells.
Nutritional scientists use the phrase “conditionally essential” to describe carnitine because under certain conditions of physical stress, disease, or trauma, it may be imperative to consume carnitine. We only produce about 20 milligrams of carnitine internally (de-novo synthesis) on a daily basis. The amounts we get from our diet vary tremendously according to dietary practices. The estimates of carnitine consumption are 72 mg/person/day in Japan, 225 mg /person/day in the U.S., and 290 mg/person/day in New Zealand.
While dietary supplement consumers have favorably embraced carnitines, the array of different carnitine forms available in the market has resulted in consumer confusion. Choices include Carnitine Tartrate, Carnitine Fumarate, Acetyl-L-Carnitine, Acetyl-L-Carnitine Arginate, Propionyl- L-Carnitine, to name a few. Which is the best form and what are the differences? To answer these questions requires a slight investigation to uncover the differences in forms and effects of these various carnitines.
One of the main reasons for the different commercial forms of carnitine is because the carnitine molecule is inherently unstable. It has a powerful ability to attract moisture (hygroscopicity), thus resulting in difficulties of formulating in a finished dosage format. This led the two primary pioneers of carnitine manufacturing, Sigma Tau and Lonza, to employ the use of stabilizing salts to eliminate the hygroscopic effect and stabilize carnitine. The addition of the salts tartrate or fumarate results in a stable carnitine for a finished dosage format. These forms of carnitine are called salts of carnitine, as they are not molecular bonds per se, but rather weak ionic interaction. In other words, when you consume a carnitine tartrate or a carnitine fumarate, it results in a release of free of carnitine and the stabilizing salt. Sure, there are differences in the effects of the salt themselves, but in my opinion the differences are minor as the real active compound is the carnitine.
Some forms of carnitine are not stabilized salts but completely different molecules with differences in biological effects. These are not carnitine salts but rather molecular analogs of carnitine. Some examples of these analogs are Acetylcarnitine (also known as Alcar or ALC), Propionylcarnitine (PLC), Carnitine Creatinate, Carnitine Taurinate, and Carnitine Arginate. As a result of the additional compounds bonded to the carnitine molecule, these carnitine analogs offer different biological effects. Unfortunately, for most of these products, there have not been comparative clinical trials conducted to determine if these biological effects are specific to the carnitine analog or to carnitines in general. But, the following can provide some understanding of the carnitine analogs:
“Carnitine Plus” molecules
This is a group of carnitine-based molecules whereby an additional nutrient is bonded to the carnitine. The additional molecule can be Arginine, Creatine, Taurine, Lysine, or other nutrient. These carnitine analogs are likely cleaved into free carnitine plus the accompanying nutrient prior to absorption into the body. Sure, taking a carnitine creatinate is superior to taking ordinary carnitine, but it’s not a fair comparison. A more interesting comparison would be to investigate if there’s any difference after oral administration of a carnitine-plus-nutrient molecule versus a carnitine-and-nutrient mixture - - the latter being a simple mixture of two powders, not a molecular bond, and a lot less costly. So, in general, the “carnitine plus” molecules are still in a phase of proving their worth. Two carnitine analogs, though, are deserving of a special mention because of their difference from ordinary carnitines as well as the amount of clinical data substantiating their use: Propionylcarnitine and Acetylcarnitine.
Propionylcarnitine (PLC) is available commercially in the form of glycine-propionylcarnitine (esterified carnitine) and this is a superb form of carnitine very specific for muscle tissue and cardiovascular protection. In an experimental rodent study, ordinary carnitine and acetylcarnitine had no protective effect on vascular inflammation, but PLC offered significant protection. Although ordinary carnitine and acetylcarnitine have proven cardiovascular benefit, there are some effects of PLC that are superior for particular cardiovascular conditions.
This is one of my favorite forms of carnitine because of its versatility in affecting a variety of tissues including the brain, nerve, and muscle tissue. Ordinary carnitine cannot cross the blood brain barrier (BBB), however acetylcarnitine crosses the BBB and has been proven clinically to benefit the brain. Acetylcarnitine is also a better stimulator of the mitochondria for energy synthesis than ordinary carnitine. The surprising twist is that no pharmacokinetic study has been done with acetylcarnitine to determine if it is absorbed intact. However, it has been determined in a study that consuming acetylcarnitine raises acetylcarnitine levels in the blood, and therefore yielding the desired result. If I had to simplify my life and choose one form of carnitine, based on versatility, price, and proven efficacy, I would choose acetylcarnitine.
A few other points should also be considered in order to best utilize carnitine. First, carnitine is not caffeine, so don’t expect a result in one hour. Carnitine’s effects are really felt after about four weeks of supplementation. Second, use carnitine in conjunction with synergestic nutrients such as D-Ribose (an ATP stimulator), CoQ10, and Magnesium. As to the form of carnitine, remember that there are significant differences in the members of the carnitine family. Use the above as a guide to maximize your results from the benefits of carnitines. In the final analysis, the type of carnitine you choose should be based on your specific health condition and budget.