Why do some people smell their urine after eating asparagus?

The odor of urine after eating asparagus is due to the presence of sulfur-containing compounds that are released when asparagus is broken down in the digestive system.

These compounds, especially aspartic acid, are broken down in the body into volatile sulfur compounds such as methanethiol, dimethyl sulfide, and dimethyl disulfide. These compounds have a strong, pungent odor, which in some people is released into the urine, causing a distinctive odor.

Not everyone breaks down asparagus in the same way. In some people, the sulfur compounds are produced more quickly and in larger quantities, giving their urine a stronger odor.

Research suggests that not everyone is able to detect the odor. This is due to genetic variations in the sense of smell. Some people have a genetic mutation that makes them unable to smell the sulfur compounds that are present in the urine after eating asparagus. This phenomenon is called asparagus anosmia, which means that these people are olfactory blind to the specific odor.

In summary, some people can smell their urine after eating asparagus because they both produce the sulfur-containing compounds and can detect the odor, while others either do not produce the compounds or are unable to detect the odor.

Source: https://health.clevelandclinic.org/why-does-asparagus-make-your-pee-smell

Author: Prof. Dr. Dirk Devroey - Latest update: 2024-10-06 - Copyright: Clinifacts 2025