L-carnitine is a naturally occurring amino acid that has been shown to provide numerous health benefits. It is being studied for its brain-boosting ability, ability to alleviate the effects of aging (such as neurological decline and cardiac aging) and improving insulin sensitivity and blood vessel health.
There are several different forms of carnitine, including L-Carnitine, Acetyl-L-carnitine, L-Carnitine L-Tartrate and Propionyl-L-Carnitine.
L-carnitine helps to prevent age-related diseases and decline. Researchers have found a link between a decline in mitochondrial quality and activity and the development of a many age-related diseases. Mitochondria are found in the cells and are known as “powerhouses of the cell,” due to their role in producing most of the chemical energy that cells need to survive.
As we age, there is a decrease in mitochondrial membrane potential, enzyme efficacy and reductions in the efficacy of enzyme organelles. This leads to a domino-like effect of physiological health problems.
While further studies are needed to better understand the role mitochondria plays in aging, researchers believe that finding ways to improve mitochondrial function or quality might be an effective strategy to combatting aging.
In one study performed at the University of California, Berkeley, and Children’s Hospital Oakland Research Institute, researchers tested their theory by feeding older rats acetyl-L-carnitine and alpha-lipoic acid (an antioxidant).
The impressive results revealed that not only did the rats perform better on memory tests, they had more energy, and energy-producing organelles in their cells worked better (1).
L-carnitine helps prevent cardiovascular disease. In 2013, researchers from the Mayo Clinic performed a systematic review and meta-analysis of 13 controlled trials to determine L-carnitine’s effects on mortality, ventricular arrhythmias, angina, heart failure and the reoccurrence of heart attack (infarction).
Compared with placebo or control, L-carnitine is associated with a 27 percent reduction in mortality, a 65 percent reduction in ventricular arrhythmias, and a 40 percent reduction in symptoms of angina in patients experiencing an acute heart attack (2).
In another study involving subjects at increased cardiovascular risk, acetyl-L-carnitine improved arterial hypertension, insulin resistance and impaired glucose tolerance (3).
Propionyl-L-Carnitine has been shown to aid peripheral arterial disease (circulatory problem in which narrowed arteries reduce blood flow to the limbs) as it increases peripheral microcirculation (4).
L-carnitine helps boost memory and improves cognitive decline. The results of a study published in an issue of the Journal of Neuroscience Research, showed that prolonged administration of acetyl-L-carnitine increased cholinergic synaptic transmission (choline is a precursor to acetylcholine, an important neurotransmitter for memory) and consequently enhanced learning capacity (5,6).
L-carnitine improves insulin resistance. In 2010, researchers set out to investigate the role of L-carnitine supplementation in influencing insulin sensitivity.
Patients were randomly assigned to receive a reduced calorie diet for 10 days or a reduced calorie diet along with oral supplementation of L-carnitine (2 g twice daily).
The oral glucose tolerance test improved in both groups at the two hour mark. Plasma insulin levels and homeostasis model assessment of insulin resistance significantly decreased when compared to baseline values only in the L-carnitine-supplemented group.
When used along with a restricted diet, supplementation of L-carnitine improves insulin resistance and may represent an adjunctive treatment for type 2 diabetes mellitus (7).
Another study found that carnitine supplementation (2g per day) resulted in a significant decrease in plasma FFA, which is seen as the main cause of insulin resistance and gestational diabetes (8).
L-carnitine helps improve leg and arm pain after exercise. Intermittent claudication is a condition caused by too little blood flow, usually during exercise, resulting in leg (and sometimes arm) cramping (9).
In one study, supplementation of propinyl-L-carnitine allowed participants to increase their walking distance and was most effective in those with severe leg cramping versus those with less severe symptoms (10).
L-carnitine supplementation helps improve recovery time after exercise. Two grams of l-carnitine supplementation has been shown to significantly reduce free radical formation, muscle tissue disruption and muscle soreness after physical exertion (11).
Two grams of supplementation of L-carnitine L-tartrate in 10 resistance-trained men was able to effectively assist recovery from high-repetition squat exercise (12).
In a study in patients with kidney disease, supplementation for two months with L-carnitine showed promise in decreasing oxidative stress responses, enhancing antioxidant status and improving exercise performance (13).
Participants performed an exercise test to exhaustion before and after supplementation.
L-carnitine may help fight fatigue. In a study involving young and old rats, researchers noted that supplementation of acetyl-L-carnitine significantly increased the distance traveled in both young and old rats, with the increase being larger in the old rats (14).
Fatigue is often a main complaint in the elderly. Researchers have found that supplementation with acetyl L-carnitine holds promise in reducing both physical and mental fatigue.
In a study performed in 2008, researchers found that in addition to providing a physical and mental boost to the group of participants, supplementation improved cognition (15).
In another study performed on 66 participants age 100 and older, supplementation with L-carnitine showed improvements in the following areas: total fat mass, total muscle mass and plasma concentrations of total carnitine.
Compared to placebo, significant improvements were also found in physical fatigue, mental fatigue, fatigue severity and scores on the Mini-Mental State Examination (16).
Some reported side effects with L-carnitine supplementation include upset stomach, heartburn, sore throat, headache, diarrhea, high blood pressure and an unpleasant body odor when taken at high doses (17).
L-carnitine should not be used by those who are taking blood-thinning medications such as warfarin.
The proper dosage depends on what is being treated. Standard dosage ranges from 500-2,000mg per day.
Dosage also varies depending on which form is taken (L-Carnitine, Acetyl-L-carnitine, L-Carnitine L-Tartrate or Propionyl-L-Carnitine)
L-carnitine is an amino acid that has been shown to provide numerous health benefits. Studies show its ability to boost memory and improve cognitive decline; improve insulin resistance; improve neurological decline and cardiac aging; prevent cardiovascular disease; repair muscles and help improve recovery time after exercise and help fight fatigue.
There are different forms of carnitine, including L-Carnitine, Acetyl-L-carnitine, L-Carnitine L-Tartrate and Propionyl-L-Carnitine. The recommended dosage depends on what is being treated and the form of supplementation taken.
While further studies with larger randomized controlled trials of L-carnitine are needed, results so far have caught the attention of researchers.