D-lactic acid is a type of organic acid that is produced during the fermentation of carbohydrates. It is one of the two optical isomers of lactic acid, the other being L-lactic acid. D-lactic acid is commonly found in certain fermented foods and is also produced by some bacteria in the gut. In the body, D-lactic acid can accumulate in certain conditions, such as in individuals with short bowel syndrome. High levels of D-lactic acid can lead to a condition known as D-lactic acidosis, which can cause symptoms like confusion and difficulty walking. Understanding D-lactic acid is important in both food science and medical research.