Betaine

Glycine betaine

The original betaine, N,N,N-trimethylglycine, was named after its discovery in sugar beet (Beta vulgaris subsp. vulgaris) in the nineteenth century. It is a small N-trimethylated amino acid. It is a zwitterion, which cannot isomerize because there is no labile hydrogen atom attached to the nitrogen atom. This substance may be called glycine betaine to distinguish it from other betaines.

Uses

Biochemistry

Phosphonium betaines are intermediates in the Wittig reaction. The addition of betaine to polymerase chain reactions improves the amplification of DNA by reducing the formation of secondary structure in GC-rich regions. The addition of betaine may enhance the specificity of the polymerase chain reaction by eliminating the base pair composition dependence of DNA melting.

Food additive

In 2017, the European Food Safety Authority concluded that betaine was safe "as a novel food to be used at a maximum intake level of 6 mg/kg body weight per day in addition to the intake from the background diet."

Approved drug

A prescription drug (Cystadane) containing betaine has limited use for oral treatment of genetic homocystinuria to lower levels of homocysteine in circulating blood.

Dietary supplement

Trimethylglycine, a betaine, is used as a dietary supplement, although there is no evidence that it is effective or safe. Common side effects of taking oral betaine include nausea and stomach upset.

Safety

Many betaines are irritants of the eyes and skin.