Most people wear an intact version of TAAR5 and easily recognize the fishy scent as slightly off-putting – a skill that may have evolved to help our ancestors avoid spoiled food. However, a small number of the Icelanders in the study carried at least one “broken” copy of the gene that appeared to make them impervious to the odor. Some even asked it as a sugary dessert, ketchup, or something flowery.
"You really weren't even in the right stadium," said Dr. Gísladóttir.
A dull sense of bad smelling fish may sound poorly customizable. TMA doesn't always mean trouble, though, especially in Iceland where fish plays a prominent role on many menus. The country is famous for tickling dishes like lazy shark and fermented skate, which contain about as much odor as you can imagine.
This could be why the TAAR5 mutation occurs in more than 2 percent of Icelanders, but a much lower percentage of people in Sweden, southern Europe and Africa, the researchers said.
"If they hadn't looked at this population, they might not have found the variant," said Bettina Malnic, an olfactory expert at the University of São Paulo in Brazil who was not involved in the study.
Paule Joseph, a sensory expert at the National Institutes of Health, noted that these genetic changes affect or can be influenced by eating habits. "It would be good to see a similar study in a different population and a more diverse group of people," said Dr. Joseph.
Dr. Stefánsson said it was a shame he doesn't carry the rare mutation, considering how much cod liver oil he had to swallow at his mother's orders as a child. Even so, he eventually found a way to get out of work.
"I said to my mother," I won't have another spoon if you don't do it yourself, "he recalled." I've never taken cod liver oil again. "