March 25th, 2015
Why does broccoli taste awful to some, but other people crave it? How can people have different reactions to black coffee? The answer lies in our genes, which have adapted to different foods.
• More tongue. Some people, called “super tasters,” have an unusually large number of sensitive structures called fungiform papillae, on the tip of the tongue. These structures may contribute to the intense flavors sensed by the super-taster.
• The right chemistry. A chemical test, called 6-n-propylthiouracil (PROP), found that about 25% of us are “super tasters,” another 25% are non-tasters, and the remaining 50% do sense bitter taste, but far less so than supertasters. PROP is similar to a naturally occurring chemical, called PTC, which conveys a bitter taste to a “taster.”
• A gene for bad taste. “Supertasters” have a variant of a taste gene called TAS2R38 that controls the nervous system’s reaction to the PROP test. More women and chefs have the supertaster variant of TAS2R38; children, however, may have all sorts of variations and their reactions to vegetables are determined more by social interaction and culture than by their genes.
• A hidden advantage. Noam Cohen at the University of Pennsylvania found that “super tasters” may be better able to fend off bacterial respiratory infections. The receptor controlled by the TAS2R38 gene (called T2R38), alerts the respiratory system when pathogenic bacteria invade. Super taster T2R38 receptors, can sound this alert with just 1% of the bacterial signal.
Modern genomic screening has found more genes (or small variants in genes) that can determine how we taste foods. Scientists at 23andMe found that a small genetic change known as a SNP (single nucleotide polymorphism) was responsible for the 9% of people who thought that cilantro (coriander) tasted like soap. It’s estimated that about 25 bitter taste receptor genes exist, though next-generation sequencing will quite likely yield many more significant genetic combinations.
Oddly, these taster genes do not seem to correlate well with actual eating habits. In short, people eat food despite the bitterness.
Why have a difference in taste? As humans evolved, they were exposed to far more toxic plants in their environment than they are today. This was particularly true when humans were hunter-gatherers, and had to identify “good” versus toxic food despite their nomadic behavior. Once agriculture became commonplace, toxic plants could be avoided, if not bred out of a cultivated plant.
Photo: Science Friday
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