PEOPLE’S LOVE for sweet is so ingrained that food companies entice consumers to their products by adding sugar to almost everything they make: yogurt, ketchup, fruit snacks, breakfast cereals and even health foods like granola bars.
It’s hard to imagine a greater disconnect between a powerful attraction to something and a rational aversion for it. Insights into our species’ evolutionary history can provide important clues about why it’s so hard to say no to sweet. In nature, sweetness signals the presence of sugars, an excellent source of calories.
This ability allowed foragers to assess calorie content with a quick taste before investing a lot of effort in gathering, processing and eating the items. Detecting sweetness helped early humans gather plenty of calories with less effort. Rather than browsing randomly, they could target their efforts, improving their evolutionary success.
Evidence of sugar detection’s vital importance can be found at the most fundamental level of biology, the gene. Your ability to perceive sweetness isn’t incidental; it is etched in your body’s genetic blueprints.
Sweet perception begins in taste buds. Different subtypes of cells within taste buds are each responsive to a particular taste quality: sour, salty, savory, bitter or sweet. The subtypes produce receptor proteins corresponding to their taste qualities, which sense the chemical makeup of foods as they pass by in the mouth.
Sweet-detecting cells produce a receptor protein called TAS1R2/3, which detects sugars. When it does, it sends a neural signal to the brain for processing. This message is how you perceive the sweetness in a food you’ve eaten. The sugar-detecting receptor protein TAS1R2/3 is encoded by a pair of genes on chromosome 1 of the human genome, conveniently named TAS1R2 and TAS1R3.
Comparisons with other species reveal just how deeply sweet perception is embedded in human beings. The TAS1R2 and TAS1R3 genes aren’t only found in humans but most other vertebrates have them, too. They’re found in monkeys, cattle, rodents, dogs, bats, lizards, fish and other animals.
Geneticists have long known that genes with important functions are kept intact by natural selection, while genes without a vital job tend to decay and sometimes disappear completely as species evolve. Scientists think about this as the use-it-or-lose-it theory of evolutionary genetics. The presence of the TAS1R1 and TAS2R2 genes across so many species testifies to the advantages sweet taste has provided for ages.
Anyone who decides they want to reduce their sugar consumption is up against millions of years of evolutionary pressure to find and consume it. People in the developed world now live in a society that produces more sweet, refined sugars than can possibly be eaten. There is a destructive mismatch between the evolved drive to consume sugar, current access to it and the human body’s responses to it.
Here’s a sweet message for lovers: A Belated Happy Valentine’s Day! By Manny Palomar, PhD (EV Mail FEB. 17-23, 2025 issue)
