Betaine is a naturally occurring compound found in a variety of foods, including beets, spinach, and whole grains. However, during the manufacturing of betaine supplements, impurities may be introduced into the final product. These impurities can come from the starting materials, the manufacturing process itself, or from contamination during storage or transportation. Some common betaine impurities include trimethylamine oxide (TMAO), betaine hydrochloride, and dimethylglycine (DMG), which can have potential health risks if consumed in excessive amounts. It is important to choose high-quality betaine supplements that have been rigorously tested for purity and safety.