Introduction
Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness, cataplexy (sudden loss of muscle tone in response to strong emotions), and rapid eye movement (REM) sleep abnormalities. Narcolepsy patients are at a higher risk of obesity and non–insulin-dependent diabetes mellitus and show high levels of total cholesterol and triglycerides.
True narcolepsy affects only about 5 out of every 10,000 people in the United States in Europe, but affects about 1 in every 500 people in Japan and Asia. There are several genetic markers that have been linked to the condition. One of the most common is a genetic predisposition for low carnitine levels.
Background Data:
Carnitine is a vitamin-like compound responsible for the transport of long-chain fatty acids into the energy producing units in cells – the mitochondria. Carnitine can be synthesized from the essential amino acid lysine, so it is not officially listed as a vitamin. Sometimes, however, there is insufficient production of carnitine. As a result carnitine supplementation has shown considerable benefit in the treatment of a wide variety of conditions associated with impaired fat utilization and energy production including:
- Alzheimer’s disease and age-related senility
- Cardiovascular disease
- Angina
- Congestive heart failure
- High blood lipids (cholesterol and triglycerides)
- Peripheral vascular disease
- Kidney disease
- Liver disease
- Macular degeneration
- Male infertility (carnitine improves sperm counts and motility)
Low levels of carnitine are associated with a higher frequency of fragmented wakefulness and REM sleep.
New Data:
In a study conducted at the University of Tokyo, 30 patients with narcolepsy were given L-carnitine (510 mg/day) or a placebo in a randomized, double-blind, cross-over and placebo-controlled trial. Results revealed that total time for dozing off during daytime in narcolepsy patients, the primary endpoint, was significantly decreased by L-carnitine supplementation compared with placebo. L-carnitine supplementation also increased serum carnitine levels and reduced serum triglycerides concentration indicating improvement in the burning of fat as energy.
Commentary:
The significance of this study is high. Although narcolepsy is a rather rare disorder, daytime sleepiness is not. It is possible that low levels of carnitine could be a cause of fatigue and daytime sleepiness. For example, low serum carnitine levels have been observed in patients with chronic fatigue syndrome (CFS) – a clinically defined condition characterized by severe disabling fatigue and a combination of symptoms, such as musculoskeletal pain, difficulty in concentration and sleep disturbances.
L-carnitine supplementation has produced significant improvements in fatigue severity after two months of supplementation. The authors of the new study concluded “there might be a common pathological process underlying narcolepsy and CFS since both are accompanied by low serum carnitine levels, a symptom that is improved by L-carnitine treatment.”
Typical dosage recommendations for L-carnitine are 900 to 1,500 mg daily.
Reference:
Miyagawa T, Kawamura H, Obuchi M, et al. Effects of oral L-carnitine administration in narcolepsy patients: a randomized, double-blind, cross-over and placebo-controlled trial. PLoS One. 2013;8(1):e53707.
