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Wednesday, 3 August 2011

L-Carnitine Supplementation - What is New?


What is L-Carnitine?

L-Carnitine is an amino acid and meats such lamb, beef and pork (mainly red meat) contain high levels of L-Carnitine. It is also found in dairy products albeit at much lower levels. In the body, 95% of L-Carnitine is found in skeletal muscle and heart muscle with the remainder of the 5% present in the kidneys and liver.

What does L-Carnitine do?

L-Carnitine plays a significant role in fat metabolism. More specifically, L-Carnitine transports fatty acids (these are what fats get broken down to) across the mitochondria (the powerhouse of all cells). In simple terms, L-Carnitine transports fat into the cell so that the fat can be oxidised or burned and used as a fuel.   

L-Carnitine and Scientific Research

As a supplement, L-Carnitine has been around for a while (since the 1980s) however until recently, the research on L-Carnitine has not been convincing. It has been purported to increase fat burning, increase endurance performance (mainly from using more fats as a fuel and sparing glycogen), and improving high intensity exercise performance (by reducing lactate production). L-Carnitine is mainly known and advertised by supplement companies as a fat burner.

It is important to note that several studies have failed to demonstrate the above claims (see links below). Although some studies have shown some benefits majority of the studies on L-Carnitine have been unsuccessful at showing that L-Carnitine is a useful supplement for athletes.

Some studies showing no effect of L-Carnitine on performance and fuel use:

·      Effects of four weeks L-Carnitine L-tartrate ingestion on substrate utilization during prolonged exercise.

·      Effects of L-Carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double-blind crossover field study.

·       Supplemental Carnitine and exercise



New Research on L-Carnitine   

More recently however (http://www.ncbi.nlm.nih.gov/pubmed/16984983), scientists have found that when L-Carnitine is taken with carbohydrate (carbohydrate raises insulin and insulin helps the muscles absorb more L-Carnitine) the following was observed:

·      Total Carnitine content in muscle was higher
·      Muscle glycogen content increased
·      Decreases carbohydrate oxidation
·      Increased fatty acid oxidation

In summary it was found that when Carnitine was taken with a carbohydrate drink (i.e. similar to a Lucozade sports drink), more Carnitine was absorbed by the muscle which resulted in higher fat use that consequently saved carbohydrate. It was also found that more muscle glycogen was present in the muscle when Carnitine was taken compared to carbohydrate alone.

J Physiol. 2011 Feb 15;589(Pt 4):963-73.
Chronic oral ingestion of L-Carnitine and carbohydrate increases muscle Carnitine content and alters muscle fuel metabolism during exercise in humans


This recent study by Wall et al. (2011) found that muscle Carnitine levels can actually be raised by taking 80 g of carbohydrate and 2 g of L-Carnitine twice per day over 6 months! Moreover, this study also found that muscle glycogen use during low intensity exercise (@ 50% VO2max) was reduced and fat use during low intensity was increased. In addition when participants taking the Carnitine exercising at 80% VO2max, lactate was lower.

These findings indicate that when  2 g of L-Carnitine is taken with 80 g of carbohydrate twice daily over 6 months, more fat is used during exercise, more glycogen is spared and lactate is reduced at higher intensity exercise. These are pretty impressive findings because in endurance sports such as triathlon and marathon running, athletes could spare muscle glycogen and use more fats as fuel during a race with L-Carnitine + carbohydrate supplementation. Similarly, in sprint/team sports (i.e. rugby, football etc.) reduced lactate levels are achieved allowing for higher work rates and quicker recovery.

Practical Implications

Although further research on Carnitine is needed to confirm and further these findings, they look promising. Realistically, taking 2 g of L-Carnitine with 80 g of carbohydrate for 6 months twice daily is a massive ask, particularly for athletes who try to control their carbohydrate intake. If the L-Carnitine is taken with a recovery drink after training (for athletes who train twice daily) can mimic the above study (although 80 g may be a little high for a recovery drink) athletes could see a positive benefit.

Currently the only product that I am aware of in the UK that is safe (for those that get drug tested) and reputable is the Science in sport burner gel (http://www.scienceinsport.com/public/shop_product.php?selprod=9) however, it only contain 1 g of L-Carnitine and just under 20 g of carbohydrate (much less than what was used in the above study).

It is still early to tell whether L-Carnitine can be effective to enhance performance in endurance and tea, sports but for those of you that are keen in trying it the following protocol should help:

·      Take 2 SIS burner gels per day (one should be taken during/after training and the other one after a second session or as a snack if not training)

·      It takes time for the muscle to absorb the L-Carnitine so this strategy needs to be followed for at least 3 months or longer

·      The SIS Gels contain much lower levels of Carbohydrate and L-Carnitine as used in the above study and these dosages haven’t fully been investigated at the protocol used above contained 700 kcal per day!

Summary

Watch this space on L-Carnitine. I will update this blog as Professor Paul Greenhaff from Nottingham Uni and other researchers in the field publish more work.



By Mayur Ranchordas






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