Betaine is a broad term in chemistry that describes any neutral chemical compound with both a positively charged or cationic functional group and a negatively charged or anionic functional group. Functional groups are specific groups of atoms that give the molecules they are attached to specific chemical properties. In a betaine, these functional groups may not be adjacent to each other in the molecular structure. Betaines have several dietary functions, and help to prevent heart and liver disease.
The cationic functional group of a betaine is usually an onium ion. An onium ion is an ion (atom with a positive or negative charge) formed by adding a proton to a neutral molecule. The ammonium ion has the formula NH4+, and is an onium ion. NH3, ammonia, is a neutral molecule. The addition of a proton results in ammonium, thus ammonium is an onium ion.
The term betaine was originally coined to describe the specific molecule trimethylglycine. Trimethylglycine was named after its discovery in sugar beets, scientifically referred to as Beta vulgaris. With the formula (CH3)3N+CH2CO2H, trimethylglycine is a betaine. It has several therapeutic uses, and is sometimes used as an aid to digestion. It is often called glycine betaine to separate it from the general category of betaines.
Usually, betaines are zwitterions. A zwitterion is a chemical compound that has formal positive and negative charges on different atoms but is, over all, neutral. In compounds such as these, the cationic and anionic functional groups oppose each other and cancel each other out. While different ends of the compound have distinct and different charges, the overall result is a completely neutral compound.
In many biological systems, betaines function as osmolytes, substances that affect osmosis. Betaines are usually produced or synthesized by cells, and they serve to protect against the various cellular stresses associated with osmosis. The protective actions of betaines primarily function to prevent cellular dehydration.
Increasingly, scientists are recognizing the significance of betaines as methyl donors. Methyl molecules are important aids to many biological and chemical processes in the body. Betaines, through donating methyl to bodily processes, aid liver function, cellular reproduction, and several other important processes throughout the body. They are also believed to be effective in the prevention of heart and liver disease, and can be found in beets, broccoli, grains, shellfish, and spinach. Betaine supplements are also produced from sugar beets and are available in a variety of forms.