L-carnitine is an amino acid compound used as a supplement to improve mitochondrial health and act as a bioenergetic. In plain English, that means it improves energy levels by boosting the action of the mitochondria -- the energy powerhouse in your cells.
L-carnitine has a range of sub-compounds that can have a variety of different effects. The supplement may help improve cognition and aid in recovery. It also acts as a nitric-oxide-boosting ingredient that may improve your workouts.
Carnitine acts as an antioxidant, making it a possible treatment for a variety of different health problems. Antioxidants help eliminate free radicals, which damage cells and can alter DNA. Experts theorize that since antioxidants neutralize free radicals, L-carnitine may reduce or prevent health problems.
How it works
L-carnitine works by making it easier for the body, specifically the mitochondria in your cells, to produce more energy. This leads to improved endurance, which in turn may yield better performance at the gym and increased overall activity.
This amino acid does have a relatively low bioavailability, however, with just about 15% staying intact. The remaining useable form will pass through your digestive system. Despite its low absorption rate, L-carnitine and its sub-compounds still provide several benefits.
In the body, L-carnitine is converted into a variety of related compounds. Each has different benefits. While you could supplement with a broad-range L-carnitine supplement, read about the specific benefits provided by sub-compounds, like acetyl L-carnitine, propionyl L-carnitine, and L-carnitine L-tartrate.
Acetyl L-carnitine, or ALCAR, acts as a neurotransmitter and can help with problems related to aging, especially brain cognition. The energy-boosting effect of ALCAR also promotes endurance and increases alertness, though the effect is not as strong as caffeine.
ALCAR is recommended for offsetting the effects of chronic fatigue, metabolic disorders, and dementia.
Endurance athletes considering l-carnitine supplementation should skip right to ALCAR. The fatigue-fighting effects (which are discussed in depth on our acetyl l-carnitine page) are well worth their price, especially when considering the focus boost that comes along with it.
Propionyl-L-carnitine, or PLCAR, is estimated to have a somewhat higher bioavailability than standard L-carnitine, but no studies quantify how much. It also has fewer side effects than other L-carnitine sub-compounds.
Propionyl-L-carnitine increases energy production in the muscle by converting fatty acids to acylcarnitines, which are burned as energy, resulting in weight loss. This process allows you to retain lean muscle mass since the body only burns fat, not muscle. You should note, however, that studies on weight loss using propionyl-L-carnitine has only been studied on mice, not humans.
L-carnitine L-tartrate, or LCLT, is a great supplement for recovery following a workout. Supplemental LCLT acts as an antioxidant, lowering free radical production, and can reduce soreness after exercise. In one small study, researchers demonstrated that using 2g of LCLT daily reduced muscle disruption following exercise up to 45% faster compared to a placebo group.
To help build endurance and get the most out of your workout, glycine propionyl-L-carnitine (GPLC) is extremely beneficial. It helps promote nitric oxide in your body, which in turn acts as a vasodilator. In plain language, it increases blood flow and oxygen supplied to your muscles.
Standard L-carnitine is the most widely available and least expensive of all the carnitine compounds. Each are available in liquid, powder, and capsules. Liquid forms provide faster uptake and more of the compound can be absorbed. However, liquid, as well as powders, can have a bitter aftertaste, making the pill form more appealing to some.
The recommended dosage range for supplements in the L-carnitine family are as follows:
|L-Carnitine Compound||Recommended Dosage (mg p/d)||Recommended Dosage (g p/d)|
|Standard||1,000mg to 3,000mg||1g to 3g|
| ALCAR ||630mg to 2,500mg||.63g to 2.5g|
|PLCAR||500mg to 2,000mg||.5g to 2.g|
| LCLT ||1,000mg to 4,000mg||1g to 4g|
| GPLC ||1,000mg to 4,000mg||1g to 4g|
According to the University of Maryland Medical Center, a typical dose for standard L-carnitine is between 1g to 3g per day.
Who should take it
It's hard to imagine a group that this supplement would put at a disadvantage. By helping you stay active or improving your performance, it's an excellent supplement for anyone interested in healthy living. It's especially beneficial if you suffer from chronic fatigue or age-related neurological problems.
In 2011, researchers from Maryland's Institute of Chronic Illnesses concluded that L-carnitine therapy, administered at 50mg/kg of bodyweight per day for three months, demonstrated significant improvement in clinical measurements of autism spectrum disorder severity. More studies are needed to confirm these results and move towards autism treatment methods using this amino acid.
Although its supplementation is popular for weight loss, standard l-carnitine is not shown to burn fat — even when combined with aerobic activity. Due to the lack of fat burning effects, we consider this a third-tier supplement for most individuals, and typically recommend one of the sub-compounds, such as acetyl-l-carnitine. In 2005, Swiss exercise physiology experts demonstrated that the compound does not improve recovery from fatigue-inducing workouts.
According to the University of Maryland Medical Center, L-carnitine is safe for use in combating fatigue and improving exercise performance, "but may not help much."
Potential side effects
Taking too much L-carnitine, about 5g, can cause digestive upset, abdominal pain, vomiting, and diarrhea, though these symptoms cease once you lower your dosage (start by cutting it in half), or stop taking it completely. Another good idea is to switch to a sub-compound such as ALCAR, which requires you to take less, and may yield fewer problems.
Other side effects include rash, body odor, and increased appetite, though these are rare.
As with any medication or supplement, talk to your doctor before changing or adding to your fitness regimen. If you have any of the following disorders, delay any type of carnitine supplementation until you consult with a physician:
By helping you stay active and improving your performance, L-carnitine is an excellent supplement for anyone interested in healthy living.
- Peripheral vascular disease
- High blood pressure
- Liver disease from alcoholism (cirrhosis)
- Kidney disease
- History of seizures
Red meat is the best way of supplementing L-carnitine through diet. It contains 95mg of the amino acid per 100g of beef. That means to get the lowest effective dosage of L-carnitine, at 500mg, you would need to eat more than 526g, or 18.56 oz., of steak every day. If the cost of a 20oz. daily rib eye habit doesn't dissuade you, the possible damage to your arteries and inevitable weight gain should.
We suggest the following brands for liquid and powder L-carnitine formulations:
- NOW Foods has an excellent powdered or capsule L-carnitine supplement in a variety of sizes.
- Dymatize offers a sugar- and calorie-free liquid L-carnitine that is very affordable. Where to buy
- Goo MJ, et. al.; Archives of Pharmacal Research; "Protective effects of acetyl-L-carnitine on neurodegenerative changes in chronic cerebral ischemia models and learning-memory impairment in aged rats;" January 2012
- Mingorance C, et. al.; PLoS One; "Propionyl-L-carnitine corrects metabolic and cardiovascular alterations in diet-induced obese mice and improves liver respiratory chain activity;" March 2012
- Volek JS, et. al.; American Journal of Physiology; "L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress;" February 2002
- University of Maryland Medical Center; "Carnitine (L-carnitine);" Reviewed March 2011
- Villani RG, et. al.; International Journal of Sports Nutrition and Exercise Metabolism; "L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women;" June 2000
- Stuessi, C, et. al.; European Journal of Applied Physiology; "L -Carnitine and the recovery from exhaustive endurance exercise: a randomised, double-blind, placebo-controlled trial;" December 2005
- Geier DA, et. al.; Medical Science Monitor; "A prospective double-blind, randomized clinical trial of levocarnitine to treat autism spectrum disorders;" June 2011