Carnitine is a term used to describe various compounds — including L-carnitine and acetyl-L carnitine — that help your body convert fat into energy, according to the Office of Dietary Supplements' website. Your liver and kidneys naturally produce carnitine, and your body stores it in tissues and organs. Your body also gets carnitine from foods such as red meat, milk, chicken and fish. Some athletes, such as competitive swimmers, believe that taking carnitine supplements can boost their performance, but scientific evidence doesn’t clearly point in that direction.
Swimmers and Carnitine
Because L-carnitine plays major roles in energy metabolism, some interest has swirled around its potential to boost athletic performance, according to the Linus Pauling Institute at Oregon State University. However, research published in a 1994 issue of the “International Journal of Sports Medicine” indicates that supplementation may not have its desired effect. In the study, 20 male swimmers were split into a placebo group and a group given an L-carnitine supplement before doing five 100-yard swims with two minutes of rest between bouts. The participants who had L-carnitine had significantly more carnitine in their blood, but their performance times were no better than the performance times of the placebo group members. Additionally, other markers of physical performance — such as blood pH levels — were similar among all study participants.
Other Research Findings
Some small and uncontrolled studies have indicated that supplementing with L-carnitine can increase indicators of increased athletic endurance — such as maximal oxygen uptake — according to the Linus Pauling Institute. However, the conclusions from those studies are limited because the study models had no control groups, the supplementation duration was short and the numbers of participants were small. Also, most recent research hasn’t shown that any supplementation with L-carnitine affects physical performance, according to the Linus Pauling Institute.
Warning
Don’t take a carnitine supplement without your doctor’s recommendation or supervision, particularly if you have pre-existing health conditions such as peripheral vascular disease, cirrhosis, diabetes, kidney disease, high blood pressure and a history of seizures. Supplements may also negatively interact with other medications and, in high doses, they can cause side effects such as diarrhea and rash, according to the University of Maryland Medical Center.
Considerations
As long as you’re generally healthy and you eat a variety of foods that contain carnitine, you shouldn’t need carnitine supplements to treat a deficiency. However, your doctor may prescribe supplements if you have a genetic disorder that causes a carnitine deficiency or if you have a deficiency from a disorder such as kidney failure, according to the Office of Dietary Supplements. Some symptoms of carnitine deficiency are weakness in the muscles, low blood sugar, fatigue, low weight, vomiting and liver enlargement.
References
- International Journal of Sports Medicine: The Effects of L-Carnitine Supplementation on Performance During Interval Swimming
- Office of Dietary Supplements: Carnitine
- Linus Pauling Institute: L-Carnitine
- American Journal of Clinical Nutrition: Supplemental Carnitine and Exercise
- Muscular Dystrophy Association: Carnitine Deficiency
- University of Maryland Medical Center: Supplements with Similar Side Effects as: Carnitine (L-Carnitine)
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