COPD stands for “chronic obstructive pulmonary disease”. Two lung diseases fall under the category of COPD: bronchitis and emphysema. Both conditions are largely caused by smoking and often occur together. A placebo-controlled study, appearing in the Brazilian Journal of Medical and Biological Research (2006; 39(4): 465-74,) looked at the effect supplementation with L-carnitine had on patients with COPD. It found that supplementation for six weeks with L-carnitine (2 grams per day) improved the strength of the muscles involved with inspiration and increased exercise tolerance.