Asparagus makes your pee stink due to a sulfur-containing compound called asparagusic acid, which is unique to asparagus. When digested, asparagusic acid breaks down into volatile sulfur compounds such as methanethiol and dimethyl sulfide. These substances evaporate during urination, releasing the strong, distinctive odor that some people detect. The smell can be noticed within 15 to 30 minutes after eating asparagus and can last for several hours.
Not everyone experiences or detects this smell because people vary in their metabolism of asparagusic acid and their genetic ability to smell the sulfur compounds. Some people do not produce the smelly compounds, while others produce them but cannot smell them due to genetic differences in olfactory receptors.
In summary, the characteristic odor of asparagus pee results from the metabolic breakdown of asparagusic acid into sulfur compounds that are excreted in urine and then detected by the nose during urination.
