The Genetics of Taste

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One of my co-workers has all kinds of rules about the foods she likes and dislikes: No cooked fruit (too sweet and mushy). No "sweet meat" (no barbecue sauce!). No raw tomatoes.

Another friend pretty much only likes foods that are beige: pasta, potatoes, creamy sauces. Nothing too spicy or tangy. She once came to an Indian restaurant with my family for a birthday celebration. We had to take her to McDonald's afterward.

Some people will eat just about anything, but most of us have a few food rules of our own. My big no-nos are cilantro (tastes like glass cleaner) and mushrooms (tastes like mildew and feels like snails), other than certain flavorful wild or Asian varieties. I'm also not a huge fan of saffron (which I think tastes like dirty dishwater), though I can tolerate it doesn't overwhelm other flavors. I love foods that are spicy, tangy or sweet—preferably at the same time—and garlic, lots of it.

How did we come by these strong flavor preferences, and why do they vary so much from person to person? A few weeks ago I wrote about one of the earliest influences on our food likes and dislikes, exposure to flavors via the womb and breast milk. But it isn't just Mom who has a role in determining what we like to eat: the way we perceive some flavors is coded in our DNA.

One of the first discoveries of this phenomenon was in 1931, when a chemist named Arthur Fox was working with powdered PTC (phenylthiocarbamide) and some of it blew into the air. A colleague in the room commented that the powder tasted bitter, while Fox detected no flavor at all. They conducted an experiment among friends and family, and found wide variation in how (and whether) people perceived the flavor of the PTC.

Geneticists later discovered that the perception of PTC flavor (which, although it doesn't occur in nature, is similar to naturally occurring compounds) was based in a single gene, TAS2R38, that codes for a taste receptor on the tongue. There are multiple versions of this gene, accounting for the variation in how strongly bitter flavors are detected. The Genetic Science Learning Center at the University of Utah Web site explains the science:

There are two common forms (or alleles) of the PTC gene, and at least five rare forms. One of the common forms is a tasting allele, and the other is a non-tasting allele. Each allele codes for a bitter taste receptor protein with a slightly different shape. The shape of the receptor protein determines how strongly it can bind to PTC. Since all people have two copies of every gene, combinations of the bitter taste gene variants determine whether someone finds PTC intensely bitter, somewhat bitter, or without taste at all.

In a 2005 study, researchers at the Monell Chemical Senses Center found that the version of this gene also predicted a child's preference for sweet foods. Those with one or two copies of the bitter-perceiving gene were more likely to favor foods and beverages with a high sugar content, and less likely to name milk or water as their favorite beverage. It is not known yet whether this relationship is due to the children trying to mask the bitter taste of foods or some undiscovered aspect of taste receptor biology. It is also not fully understood why bitter sensitivity sometimes decreases with age.

And what about people like my colleague, who doesn't much care for sweets? It's possible she is a supertaster, the name scientists give people who have inherited more taste buds than the average person and therefore taste flavors more intensely. These people tend to shun strong-flavored foods, including rich desserts. This may explain why supertasters are more likely to be slim.

Though our food preferences have a lot to do with genetics, or nature (as much as nearly half, according to Kings College London research on identical twins), nurture is just as important. Over our lifetimes we build many complex associations with flavors and scents that can override our DNA.

What food likes or dislikes do you think you inherited?

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