Results of a new study indicate that L-carnitine may improve exercise ability in people with poor circulation in their legs. Peripheral arterial disease impairs circulation and can lead to claudication—a sharp leg pain that limits exercise.
In a study conducted by William Hiatt, M.D., of the University of Colorado Health Sciences Center in Denver, 155 Americans and Russians age 40 to 80 were randomly selected to take either 2 g/day L-carnitine or placebo for six months. To assess their walking ability, the participants were tested on a graded treadmill at 2 mph. The grade began level and increased 2 percent every two minutes. Subjects walked until leg pain became intense.
Participants also filled out a questionnaire to determine how they perceived their walking ability and their overall functioning. Nearly all the participants were Caucasian; more than 90 percent were previous or current smokers; about half were taking other medications.
After six months, the 82 who took L-carnitine walked 39 percent longer compared with a 14 percent improvement in the placebo group. In addition, those taking the supplement experienced a self-declared boost in overall health and vitality. There were no reported side effects.
L-carnitine contributes to energy production within muscle cells, and supplementation increases the energy available to skeletal muscle. In addition, Hiatt speculates, the supplement may also improve blood vessel integrity.
PURPOSE: We tested the hypothesis that propionyl-L-carnitine would improve peak walking time in patients with claudication. Secondary aims of the study were to evaluate the effects of propionyl-L-carnitine on claudication onset time, functional status, and safety.
SUBJECTS AND METHODS: In this double-blind, randomized, placebo-controlled trial, 155 patients with disabling claudication from the United States (n = 72) or Russia (n = 83) received either placebo or propionyl-L-carnitine (2g/day orally) for 6 months. Subjects were evaluated at baseline and 3 and 6 months after randomization with a graded treadmill protocol at a constant speed of 2 miles per hour, beginning at 0% grade, with increments in the grade of 2% every 2 minutes until maximal symptoms of claudication forced cessation of exercise. Questionnaires were used to determine changes in functional status.
RESULTS: At baseline, peak walking time was 331 +/- 171 seconds in the placebo group and 331 +/- 187 seconds in the propionyl-L-carnitine group. After 6 months of treatment, subjects randomly assigned to propionyl-L-carnitine increased their peak walking time by 162 +/- 222 seconds (a 54% increase) as compared with an improvement of 75 +/- 191 seconds (a 25% increase) for those on placebo (P <0.001). Similar improvements were observed for claudication onset time. Propionyl-L-carnitine treatment significantly improved walking distance and walking speed (by the Walking Impairment Questionnaire), and enhanced physical role functioning, reduced bodily pain, and resulted in a better health transition score (by the Medical Outcome Study SF-36 Questionnaire). The incidence of adverse events and study discontinuations were similar in the two treatment groups.
CONCLUSIONS: Propionyl-L-carnitine safely improved treadmill exercise performance and enhanced functional status in patients with claudication.
Hiatt WR, Regensteiner JG, Creager MA, Hirsch AT, Cooke JP, Olin JW, Gorbunov GN, Isner J, Lukjanov YV, Tsitsiashvili MS, Zabelskaya TF, Amato A. Propionyl-L-carnitine improves exercise performance and functional status in patients with claudication. Am J Med. 2001 Jun 1;110(8):616-22.