Evidence supporting the use of: Acetyl l-carnitine
For the health condition: Endurance (lack of)

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

Acetyl L-carnitine (ALCAR) is a derivative of the amino acid L-carnitine, which is involved in the transport of fatty acids into the mitochondria for energy production. The rationale for its use in supporting endurance primarily stems from its role in cellular energy metabolism. Some scientific studies have investigated ALCAR supplementation for its potential to improve exercise performance and reduce fatigue, particularly in physically active individuals and athletes.

However, the evidence supporting ALCAR’s efficacy for enhancing endurance is mixed and generally modest. Some small-scale clinical trials and animal studies have suggested that ALCAR may improve muscular energy metabolism, decrease muscle damage, and delay the onset of fatigue during prolonged exercise. These effects are hypothesized to result from more efficient fatty acid oxidation and mitochondrial function. Additionally, there is some support for its role in reducing markers of muscle injury and oxidative stress after exercise.

Despite these mechanistic insights, larger and more rigorous human studies often fail to find significant improvements in overall endurance performance, such as time to exhaustion or maximal oxygen uptake (VO2 max), with ALCAR supplementation. The majority of positive findings are limited to specific populations (e.g., elderly, individuals with fatigue syndromes) or are of marginal practical significance in healthy athletes. Therefore, while there is a scientific basis for considering ALCAR in the context of endurance, the strength of evidence is currently low to moderate, warranting a rating of 2 out of 5.

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