Brown sugar causes teeth to rotten: Tooth decay has become a prominent health hazard associated with the consumption of sugars, especially in sucrose, an element that is very high in brown sugar. Oral bacteria such as Streptococcus mutans live in dental plaque and metabolize any sugars into lactic acid. The resultant lactic acid lowers the pH of the tooth’s surface, stripping it of minerals in the process known as tooth decay.