Why You’re Evolutionarily Programed to Love Sugar

A group of friends looks at pies in a bakery window.
Humans have been evolutionarily programmed to crave sugar. Photo credit: JLPH / Image Source / Getty Images

It’s the ingredient in food you try to avoid because you feel it’s too unhealthy, but it’s so delicious it’s hard to eat in moderation. Many of us love it, but at the same time rue its existence. It turns out this tricky additive many of us have a love/hate relationship with is also one that we as humans have been evolutionarily programmed to crave: sugar.

As we know, cakes, cookies and other sweetened foods are at the top of the food pyramid for a reason; we’re supposed to eat less of them. So why do we crave them so much? Stephen Wooding, an anthropologist and assistant professor at University of California, Merced, who studies the evolution of taste perception, may have the answer.

“The refined sugars we use today are no different from the ones found in nature — the problem is that they are much more abundant now than at any point in our evolutionary history. Humans lived for hundreds of thousands of years in environments where sugar was enticing but scarce. Now we can get as much as we want, and we want lots of it,” Wooding told EcoWatch.

As Wooding pointed out to The Conversation, getting enough food to eat was one of the most basic struggles of our ancient ancestors. The daily activities of getting enough food and shelter for themselves and their families used up a lot of calories, and those who were better at these things lived longer and had more children. In other words, “they had greater fitness, in evolutionary terms,” Wooding wrote in The Conversation.

And being able to detect the presence of sugars in prospective foods, particularly in plants, while foraging could give an individual a great advantage because, as we know, sugars are a wellspring of calories. When foods are sweet, it tells the person tasting them that sugars are present, and if the taster could also tell the amount of sugar the food might have, that would enable them to quickly decide whether or not they should invest the time and energy in “gathering, processing and eating the items,” Wooding wrote for The Conversation. “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,” Wooding wrote.

According to Wooding, taste buds have subtypes of cells that respond to different aspects of taste, like salty, bitter, savory, sour or sweet. When you eat a food, the taste bud subtypes sense the food’s chemical makeup by making receptor proteins that correspond to these different “taste qualities.” The subtype that produces the bitter protein makes it when something toxic is present, while the savory protein is responding to amino acids, the molecules that combine to make proteins. As Wooding wrote in The Conversation, “Your ability to perceive sweetness isn’t incidental; it is etched in your body’s genetic blueprints.”

The receptor protein that detects sugars is called TAS1R2/3. Found in many different animals, the genes that encode the receptor protein are called TAS1R2 and TAS1R3 and have been around for hundreds of millions of years.

“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 eons,” Wooding wrote for The Conversation.

Animals that don’t usually eat foods that contain sugars lose their ability to recognize it and thus have only remnants of the TAS1R2 gene, Wooding wrote. And just as the bitter receptors in the brain tell a person something is toxic and shouldn’t be eaten, since humans have evolved to need sugar for the calories and energy it provides, when the brain detects it, it tells you to keep eating. Since these responses have been favorable for generations, they become instincts due to natural selection. “Experiment after experiment finds the same thing: People are attracted to sugar from the moment they’re born. These responses can be shaped by later learning, but they remain at the core of human behavior,” Wooding wrote for The Conversation.

When we’ve eaten a lot of sugar and start to feel sick, that’s our bodies’ way of telling us to stop, but it doesn’t always work in time to protect us from the longer-term effects of eating too much sugar.

“Our bodies send warning signals when we’re eating too much of something, including sugars. A major problem is that for most people the signal comes too late, after we’ve eaten so much we’re already storing fat and gaining weight,” Wooding told EcoWatch. “However, this isn’t true for everybody. We all have a friend who seems to effortlessly stay at a healthy weight, but we also have friends who struggle to control it. Scientists are very interested in discovering the biological signals that tell people they feel full. The formal term for feeling satisfied after eating is satiety. I think major discoveries about the sources of satiety are coming, and are going to win some Nobel prizes.”

While people who like sugar could evolve to have less of an advantage over generations due to the health effects of eating too much of it, it would take tens of thousands of years, Wooding explained to EcoWatch. He added that the health crisis isn’t all about sugar, it’s also caused by an increased consumption of complex carbohydrates, proteins and fats.

“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 an environment where society 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. In a way, we are victims of our own success,” Wooding wrote for The Conversation.

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