Carnitine is a naturally occurring amino acid derivative essential for transport of long-chain fatty acids into mitochondria. It is advertised on the Internet as a dietary supplement that can promote weight loss, increase energy, enhance athletic performance and slow aging. Levocarnitine (Carnitor - Sigma-Tau) has been FDA approved for oral and parenteral treatment of primary carnitine deficiency since 1986. Products containing levocarnitine and its synthetic derivative acetyl-L-carnitine are available as dietary supplements in the US.

Several readers have asked the Medical Letter to evaluate the effectiveness and safety of exogenous melatonin for treatment of insomnia and jet lag. Melatonin has not been approved by the US Food and Drug Administration (FDA), but is available in health food stores and apparently is being used as self-medication to treat a wide variety of disorders.

Over-the-counter products containing melatonin are widely used as sleep aids in children and adults.

Echinacea, a plant also called purple coneflower, is widely used as a dietary supplement for prevention and treatment of colds.

Coenzyme Q10, a fat-soluble antioxidant also known as ubidecarenone, ubiquinone and CoQ10, is marketed as a dietary supplement in the US, both as a single ingredient and in various combination products.

Web sites and blogs are advising patients that periodic "cleansing" of the colon is necessary to rid the body of toxins.

Claims for the superiority of various calcium supplements are now appearing on television and in the print media. A high calcium intake combined with vitamin D can increase bone density and reduce the incidence of fractures in older women and probably also in men.

Many fermented foods contain tyramine as a byproduct formed by the bacterial breakdown of the amino acid tyrosine; it can also be formed by para-hydroxylation of phenylethylamine or dehydroxylation of DOPA and dopamine. Tyramine and some other amines found in food can cause hypertensive reactions in patients taking monoamine oxidase (MAO)inhibitors.

The FDA has approved an oral liquid formulation of glycerol phenylbutyrate (Ravicti – Hyperion) for chronic management of patients ≥2 years old with urea cycle disorders that cannot be adequately managed by a protein- restricted diet. Sodium phenylbutyrate (Buphenyl, and generics), another oral drug approved by the FDA for this indication, has a bitter taste. The new product, which contains no sodium, has little or no taste. Either drug must be used in addition to a protein-restricted diet and, if needed, dietary supplementation with amino acids and other nutrients.

An advertisement in a recent issue of Ophthalmology introduces PreserVision Eye Vitamin AREDS 2 Formula from Bausch & Lomb. No specific indication is mentioned, but the ad states that “…[the new product] builds on the original PreserVision Eye Vitamin AREDS Formula, the only formula proven to slow the progression of moderate-to-advanced AMD.”