You eat what you are

Following up on my recent post on scientists trawling the silk road in search of taste receptor variants, there’s serendipitous news out that a set of polymorphisms have been found that determines whether you think cilantro tastes like soap or like heaven!  Our good friends at 23andme analyzed their database of users who responded to the questions, “Does fresh cilantro taste like soap to you?” or “Do you like the taste of fresh (not dried) cilantro?” and found a SNP – a single letter of your DNA – that was associated with the soapiness.  But they’re not the only ones – two other unpublished studies have found other SNPs associated with the taste of soapiness.

The thing is, taste and smell perception are complicated things.  Every food – every ingredient – is a unique combination of a large set of flavors and odorants.  Turning an ingredient from godly to soapy might take the interaction of many different odorant receptors to tell your brain that what you’re smelling is more like soap than an herb.  And it’s not purely genetic, either; much of the preference (or perhaps hatred) for cilantro is learned.

A similarly noxious food is the (disgusting) brussel sprout; some people taste these as terribly bitter and disgusting – and others do not.  This is reliably linked to a single SNP and here, too, the connection is not perfect.  Still, 80% of the time, if you know your genetic variant, you’ll know what you think of brussel sprouts.  The ability to taste this bitterness isn’t just in brussel sprouts: it’s also in broccoli, coffee, and dark beers.

What these SNPs are probably doing is modifying the receptor that detects the bitter-tasting chemical in a such a way that it can no longer detect it at all.  The receptor itself isn’t what causes something to be ‘bitter’: that role is relegated to the neuron upon which the receptor is located.  A famous experiment by Cori Bargmann showed that if you have an odor receptor on one neuron, it can make smells attractive; move it to another neuron and that scent becomes repulsive.  The receptor only senses the chemical, it does not tell you how you feel about it.  Flavors are complex combinations of these chemicals, and it is the combination of neurons that are activated by these chemicals that let you know whether the flavor is bitter or sweet, delicious or disgusting.

This is why it will be so interesting to see what the results of the silk road expedition are.  Do these genetic variants arise because there is selective pressure to make these herbs as ‘attractive’ in people?  Will cultures with lower levels of the cilantro soap SNPs be more likely to use recipes that include cilantro – even if in the next valley over there are a group of people with very different sets of SNPs?  And it should make you wonder what it means to have ‘good taste’ – in food as well as everything else.

References

Nicholas Eriksson,, Shirley Wu,, Chuong B. Do,, Amy K. Kiefer,, Joyce Y. Tung,, Joanna L. Mountain,, David A. Hinds,, & Uta Francke (2012). A genetic variant near olfactory receptor genes influences cilantro preference arxiv

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