Cilantro! One of the more divisive herbs on the planet. I, for one, am perfectly happy to have people cramming the green parts of the coriander plant into my stews and salsa every single day. But for 4 to 14% of people, depending on their ancestry, it can be a total meal-ruiner, making an entire soup taste like soap.

Turns out they aren't just being picky. How cilantro tastes to you has a lot to do with your genes. Now it's normal for people to like different foods, but cilantro-haters fanaticism made scientists wonder: why do they hate it so hard? 

So, they did what scientists usually do when they have questions - they investigated. A study performed in the early 2000s at the National Twin Day Festival in Twinsburg, Ohio - which yes is actually a thing - found that 80% of identical twins shared either a like or dislike for cilantro. But only 50% of fraternal twins who share about half their genome, had the same feelings for cilantro. 

Researchers at the consumer genetics firm 23andMe decided to take a closer look. They analyzed the genomes of almost 30,000 people, asking each subject whether they liked cilantro, and what they thought it tasted like. Subjects who said that cilantro made salsa taste like bubble bath had similarities in a cluster of smell receptor genes that - surprise - detect the smell of soap. 

They tended to share one gene in particular which codes for the receptor that picks up the scent of aldehyde chemicals. Aldehydes are organic molecules that contain an aldehyde group - a carbon bonded to a hydrogen and double bonded to oxygen. There's a bunch of different aldehydes that have really distinctive smells, there's vanillin which smells like vanilla, and cinnamaldehyde which is what gives cinnamon its smell. There's more than one aldehyde responsible for cilantro's distinctive smell, and they also happen to be a bi-product of soap-making. Upon further study, researchers found that almost half of Europeans have 2 copies of the gene that codes for those aldehyde receptors, but only about 15% of European subjects said that the herb tasted like soap. By comparison, 11.5% of people who had no copies of that version of the gene also said that cilantro was soapy. 

So other genes must be contributing as well. There are at least 3 more genes that seem to be involved in this cilantro-gross-out mystery, one that codes for smell receptors though we're not sure how, and two that affect the taste of bitterness. So it looks like genetics definitely at least plays a part in whether you like cilantro or not, but some specifics still need to be worked out before you can take a doctor's note to lunch tomorrow. 

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