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.
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
- 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.
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.
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.
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.