CARNITINE, FATIGUE, AND NERVE FUNCTION
A substance needed for cellular energy production is L- carnitine. This quasi amino acid is normally found in the body, and is easily interconverted from one form to another. Some is obtained from eating red meat and dairy products, and the body can also synthesize it from other dietary amino acids. A few people with specific medical conditions have actual deficiencies which are alleviated by supplementation; for this reason it is sometimes called vitamin B(t). It has been tried as treatment for many other situations. It is sometimes touted as beneficial for body building; unfortunately, there is no evidence that it helps athletes or otherwise healthy people perform better when exercising, nor with weight loss. There is some evidence that some (not all) people with fatigue due to hepatitis, celiac disease, chronic fatigue syndrome, advanced age, multiple sclerosis or cancer can obtain modest relief when taking a supplement. One cause of male infertility may also be improved, as could some persons with certain types of heart disease, and those taking the seizure medication valproic acid. One small study (ie, statistically not very significant) indicated slight benefit in diabetic weight loss when combined with orlistat, an over the counter medication that blocks fat absorption.
Larger studies need to be done to provide more solid evidence of benefit from L-carnitine supplementation. Supplementation has been reported for fatigue in vegans, persons with ADHD, anorexia or Lyme disease; no studies have been performed in persons with these issues except with ADHD due to the fragile X syndrome, in which case it may be helpful.
Consumption can cause nausea, vomiting, abdominal cramps, heartburn, gastritis, diarrhea, and a fishy body odor. L-carnitine should not be consumed as a supplement by persons with thyroid disorders or a history of seizures without consulting their medical provider.
Another form of L-carnitine, acetyl-l-carnitine, is used for several nerve-related conditions. There is some evidence of improved cognition in those with mild age-related (over 65) or chronic alcoholic-related cognitive impairment, and in depression in the elderly. Doses tested ranged from 1500 to 4000 mg daily, divided into 2-3 doses. Pain from diabetic neuropathy may be decreased with the higher doses of this form of carnitine.
Although these two forms of carnitine can be interconverted by the body, because research has been done on one substance or the other, that product should be used. The cost of these products can vary wildly; comparison shopping is recommended. In addition, and as is true with all supplements, the FDA does not regulate these products for purity or to ensure they contain what they claim.
Natural Medicines Comprehensive Database, accessed 9/24/2012
Up-to-Date, accessed 10/9/2012