L-Carnitine: The best kept supplement secret?

What is L-carnitine?

L-carnitine plays a role in many functions of the body, but there are a few of interest to the fitness world that has made supplement manufacturers sit up and take note and develop carnitine supplements that harness its full potential. This article will talk you through what L-carnitine is, why it is of potential benefit to us and in what ways, and finally, assess some of the forms in which it comes via supplementation and what effects these have had in scientific studies.

L-carnitine is created in the body from the amino acids lysine and methionine and it is the role that carnitine plays in fatty acid metabolism that first gathered interest. Skeletal muscle is the main store for carnitine in the body and is an unusual compound (as it is not considered a vitamin, mineral or amino acid but more a 'vitamin-like' compound). It can potentially achieve this function as a weight loss aid as carnitine has a key role in allowing our body to access its body fat storage as a form of energy to be transported into our mitochondria, our cellular power plants for energy. This would obviously be of interest in those who want to lose weight if increased amounts of carnitine caused an increase in fat mobilisation and in turn fat loss.   

Could it help your endurance?

This may also be of benefit for athletes in endurance activities, as using fatty acids more easily for fuel may spare muscle glycogen for when it is required, allowing them to maintain performance at higher levels for longer. This higher level of energy may also allow those of us looking to pack on lean muscle to train harder and heavier for longer and has also demonstrated effects of buffering muscle lactate, which may also improve performance in high-intensity activities.

The combination of buffering lactate and increased energy release may also help us to recover and therefore be able to increase our exercise capacity, indirectly helping us to grow more muscle. Some research has even shown that carnitine plays a role in improving the function and amount of androgen receptors, this would allow more efficient binding to testosterone and a more anabolic, muscle-building environment.

L-Carnitine has many benefits

Brainy, Healthy and Fertile

Carnitine also has many other proposed benefits, on cognitive function, boosting immune function, improved cardiovascular function, bone health and even increased male fertility. Carnitine does however come in several forms with the carnitine attached to other compounds which may have a greater effect on some of the aforementioned benefits, due to how these are digested, absorbed and metabolised in the body. Aside from supplementation with the direct form of L-Carnitine, there are four main other forms that are commonly found in supplements:


Acetyl-L-Carnitine is one of the most commonly found forms of carnitine in supplements. The addition of the acetyl acid to the carnitine is meant to be more targeted towards increased cognitive function and mental focus alongside the benefits of fatty acid mobilisation. The attached acetyl group is proposed to make the carnitine more biologically available, increasing its effectiveness.


L-Carnitine-L-Tartrate is again a popular and well-researched form of carnitine found in many supplements. The tartrate component added to the carnitine is a powerful antioxidant, this will potentially reduce the effects of exercises induced muscle stress and damage and therefore boost recovery. Research has demonstrated that supplementation with the L-tartrate form had significantly reduced catabolic markers after weight training exercise implying an increased anabolic muscle environment and concluded that supplementation with this form has muscle recovery benefits for high repetition weight training.

Glycine Propionyl-L-Carnitine

Glycine Propionyl-L-Carnitine is another fairly common form of carnitine found in supplements. It is meant to be the most targeted for muscle recovery and growth, as the addition of the glycine is proposed to promote strong blood flow to the muscles and improved protein synthesis, this increase in blood flow may also aid in the removal of waste from the muscle cells boosting performance and recovery.

L-Carnitine Fumarate

L-Carnitine Fumarate, is a less common form found in carnitine supplements, the addition of fumarate, an intermediate in the production of energy, is proposed to enhance the fatty acid metabolising effect and increases oxygen supply to the heart which would be of obvious benefit for endurance athletes for both increased aerobic capacity and glycogen sparing effects.

Check out all these benefits

What do the studies say?

Several studies have shown significant improvements in markers of athletic performance and recovery in athletic populations at between 1-3g of carnitine per day regardless of source, with most positive results showing supplementation being taken for longer periods. This directs us to conclude that carnitine supplementation should be considered for more long term use for the best possible results. Studies that have used shorter periods of dosing in less than a week have typically shown no effect, it appears that as with one of our other favourite, research-backed supplements, creatine, that there needs to be enough time for accumulation of carnitine within the muscles to have an effect. 

So there you have it the low down on carnitine, as far as research-backed supplements go, this one definitely has our interest as something that would be beneficial to many of you out there in the fitness world, regardless of your health or fitness goals. Only time will tell in more controlled studies whether these effects are going to be of benefit for the majority of us or just in selected populations, but as it’s a completely natural, safe, relatively inexpensive and pretty well supported scientifically then we suggest giving it a go and seeing what happens! Take a look at our L-Carnitine range here.

As always Team CSN are here to help, call or email us today and we can give you professional, unbiased advice on all your nutrition and supplement needs.