Carnitine – Different Types and What Do They Do?
Carnitine is a compound that helps in energy generation in the body.
It is present in almost all body cells but most abundant in muscles, the brain, the liver, and the kidneys.
The natural food sources of carnitine include red meat, fish, dairy, and poultry (1).
Different Types of Carnitine
Carnitine exists in three forms:
- Acetyl L-Carnitine
- and Glycine Propionyl-L-Carnitine.
In addition to the difference in their names, these forms of carnitine differ in their chemical structure and the kind of health benefits they offer.
We will discuss these three types of carnitine in detail here.
Understanding these differences is important as each type has particular roles in the body and gives optimum results when used for certain indications.
L-Carnitine is the most commonly occurring form of carnitine.
When people talk about carnitine, they mostly refer to L-Carnitine.
Your body cells have specialized structures inside them that function together in a complex manner.
One of the structures within your cells is the mitochondria. Mitochondria functions to generate energy inside your cells.
L-Carnitine transports fatty acids from your food to the mitochondria within their cells where they turn into energy.
The most popular use of L-Carnitine is as a ‘fat burner’.
A meta-analysis summarizing 37 RCTs noted that carnitine supplementation causes a noticeable reduction in weight and up to 2 kg reduction in body fat.
This is when L-Carnitine is used on average for 12 weeks at a dose of 2,000 mg/day (2).
Another benefit of L-Carnitine is its effects on male reproductive health.
Studies suggest that L-Carnitine improves the production of reproductive hormones.
These include testosterone, follicle-stimulating hormone, and luteinizing hormone.
All of these hormones are crucial for male reproductive health and sperm production.
Sperms are sensitive to oxidative damage.
Due to its potent antioxidant action, L-carnitine helps to improve sperm motility and survival rates, as suggested by meta-analyses (3)
The blood vessels inside your brain are selective in what they allow to seep out into the brain.
This selectivity of the blood vessels acts as a barrier- called the blood-brain barrier. Most products might claim that they work wonders for the brain.
But most of these products don’t work as their active ingredients never reach the brain due to the blood-brain barrier.
This is where acetyl L-Carnitine is different.
As you can guess from the name, acetyl L-Carnitine is structurally different from L-carnitine.
The addition of the acetyl groups allows it to cross the blood-brain barrier easily.
This gives acetyl L-Carnitine the ability to improve brain health more efficiently.
Acetyl L-Carnitine increases the levels of a main brain chemical called ‘acetylcholine’.
Acetylcholine is a main brain neurotransmitter through which the brain cells talk to each other.
It also offers neuroprotective effects due to its antioxidant properties.
Finally, acetyl L-Carnitine can even alter the gene structure of brain neurons and can save them from different diseases, such as age-related conditions.
Results of RCTs have suggested that using acetyl L-Carnitine in doses of up to 2,000 mg/day can improve cognitive function in individuals with memory dysfunction (such as Alzheimer’s and other types of dementia) (4).
Similarly, a meta-analysis of 12 RCTs suggested that using L-carnitine in doses between 500 mg and 2,000 mg/day provides a major relief from depressive episodes (5).
Glycine Propionyl-L-Carnitine (GPLC) is a derivative of L-Carnitine. GPLC differs from L-Carnitine and Acetyl L-Carnitine due to its effects on the body.
GPLC has a special affinity for body muscles including skeletal and heart muscles. It causes an increase in energy production by kickstarting fat metabolism and preventing muscle damage due to oxidative stress.
In addition, it also modules the release of nitric oxide.
Nitric oxide dilates blood vessels and increases blood supply to body parts during demand periods, such as exercise.
In one RCT conducted at the Florida Atlantic University, participants were given 4.5 g/day GPLC or cellulose for one week.
The protocol included the participants performing 90 minutes of exercise following the use of supplements.
Results showed a 15% increase in mean and peak performance among the GPLC group.
It also showed an increase in blood supply as suggested by an almost 16% reduction in the blood lactate levels among the GPLC group (6).
Studies have also suggested promising effects of using high doses of GPLC (6-9 g/day) in individuals with heart conditions.
Results show that it improves exercise tolerance and improves overall heart function in individuals with heart disease, such as congestive cardiac failure (7).
General Health Benefits of Carnitine
As suggested by research, other benefits of carnitine use include (1):
- It triggers the energy generation processes in the body.
- It helps stimulate metabolism and can aid in weight loss.
- Due to its antioxidant benefits, it can help with visible signs of aging.
- Due to its ability to combat oxidative stress, it can help with conditions that arise from an increase in oxidative stress.
- It helps improve cognitive function and can help with disorders associated with a decline in brain neurotransmitters like dementia and Parkinson’s disease.
- Due to its antioxidant benefits, it can protect nerve fibers from damage. This ability can help fight pain and is useful in several pain disorders.
- It can aid in improving mood and sleep.
- It facilitates exercise performance and can improve recovery.
- It can even be useful in conditions like high blood pressure, heart conditions, diabetes, cancers, and neurodegenerative disorders like Alzheimer’s.
- It can improve male fertility and sexual health.
- The use of carnitine in individuals with kidney disease improves anemia, fatigue, and muscle loss.
My Preferred Sources
As mentioned in this article, carnitine is present in different forms.
The versatile nature of this substance makes it extremely useful.
Knowing its different types and understanding their benefits will help you understand when and how to take the formation of carnitine.
This will help you maximize the benefits without worrying about complications or unwanted side effects.
Coach Carlos Castro
- NHI National Health Institute
- Talenezhad N, Mohammadi M, Ramezani-Jolfaie N, Mozaffari-Khosravi H, Salehi-Abargouei A. Effects of l-carnitine supplementation on weight loss and body composition: A systematic review and meta-analysis of 37 randomized controlled clinical trials with dose-response analysis. Clin Nutr ESPEN. 2020 Jun;37:9-23
- Zhou X, Liu F, Zhai S. Effect of L-carnitine and/or L-acetyl-carnitine in nutrition treatment for male infertility: a systematic review. Asia Pac J Clin Nutr. 2007;16 Suppl 1:383-90
- Traina G. The neurobiology of acetyl-L-carnitine. Front Biosci (Landmark Ed). 2016 Jun 1;21(7):1314-29.
- Veronese N, Stubbs B, Solmi M, Ajnakina O, Carvalho AF, Maggi S. Acetyl-L-Carnitine Supplementation and the Treatment of Depressive Symptoms: A Systematic Review and Meta-Analysis. Psychosom Med. 2018 Feb/Mar;80(2):154-159.
- Jacobs PL, Goldstein ER, Blackburn W, Orem I, Hughes JJ. Glycine propionyl-L-carnitine produces enhanced anaerobic work capacity with reduced lactate accumulation in resistance-trained males. J Int Soc Sports Nutr. 2009 Apr 2;6:9
- Ferrari R, Merli E, Cicchitelli G, Mele D, Fucili A, Ceconi C. Therapeutic effects of L-carnitine and propionyl-L-carnitine on cardiovascular diseases: a review. Ann N Y Acad Sci. 2004 Nov;1033:79-91