Researchers have tied having a certain gene variant to having bad breath, the Sacramento Bee reports. It notes that while some cases of bad breath can be due to what someone just ate, other times it's chronic.
"It's important to identify the cause of persistent halitosis, and differentiate that cause from relatively benign causes … and the more morbid causes such as liver cirrhosis," the University of California, Davis' Kent Lloyd says in a statement.
He and his colleagues studied five people from three unrelated families with a history of cabbage-like bad breath. As they report in Nature Genetics this week, they uncovered mutations in the SELENBP1 gene among the five affected people. This gene encodes a methanethiol oxidase, which breaks down the sulfur-containing compound methanethiol, which is produced when food is digested.
As Gizmodo notes, the researchers suspect that mutations in SELENBP1 lead to some methanethiol not being broken down and cause the bad odor.
Lloyd and his colleagues also note that SELENBP1 has previously been tied to cancer, though its role is unclear. Gizmodo writes that SELENBP1 mutations in cancers could also led to a buildup of odorous compounds and possibly explain why some dogs can smell cancer.