Here’s why we crave more and more sweetness — and how
to stop the cycle 05/27/2020
Ambition? I only want to walk in beautiful places and eat sweet things.” Marty Rubin, American author.
Human beings are born “wired” for sweet tastes. No wonder. For our ancestors, finding a bit of sweet fruit or perhaps a honeycomb could provide essential, concentrated calories and energy, vital for times of food scarcity.
And human history has known plenty of food scarcity.
The problem, of course, is that the modern era presents us with the precise opposite of scarcity – an endless cornucopia of every kind of food imaginable, especially the most tempting sweet ones.
Worse, there seems to be a habituation response. Eat lots of sweet treats, and soon you need more - or more concentrated - sweets to get the same intensity of pleasurable taste, which puts on the pounds and can eventually lead to serious disease including type 2 diabetes.
The good news: this process can run in reverse. By intentionally restricting sweet foods, you can ramp up your ability to appreciate even subtle sweetness.
As it turns out, this does not appear to be “just” a psychological effect.
Lords of the Fruit Flies
Researchers at the University of Sydney in Australia, studying fruit flies, discovered that taste perception is constantly changed at a molecular level by every food the flies consumed (Wang Q-P et al. 2020).
And before you object that flies are not people, one of the researchers was careful to note that the molecules involved are “conserved” in evolution all the way to humans. “We know humans also experience changes in taste perception in response to diet, so it's possible the whole process is conserved…” said Qiaoping Wang of China’s Sun Yat-Sen University.
Central to the taste-perception-habituation process is dopamine, the neurotransmitter that humans also use to notice, learn and remember.
The researchers found that when the flies ate unsweetened food, this made sugary food eaten afterward taste more intense, as represented by increased neurotransmitter traffic in the flies’ tongues.
This means the dialing up or down of perceived sweetness is in the tongue itself rather than the flies’ brains (yes, fruit flies have brains, albeit small ones, and may even have primitive emotions [C.I.T., 2020]) and is a specific, observable physical process, “which is kind of neat,” said Wang.
Putting it to Use
One of the secrets of healthy eating is consuming food in such a way that we conserve our ability to perceive its intense, pleasurable, satisfying flavor.
The fruit fly study and others suggest that one way to do this is to eat less of, or stop eating altogether, the sweet treats that we love on a regular basis, to restore our ability to be satisfied by a smaller or less concentrated amount.
One human study confirming this found that study participants did not derive increased pleasure from sweet tastes in four sweetened beverages, but rather habituated to them as measured by survey results. The study concluded, “weak” responses as the tasting went on reflected “habituation…to sweet taste than a gradation in sensory pleasure” (Leterme A et al. 2008)
Aside from taking periodic breaks from sweets, another way to preserve our taste sensations and enjoyment is via eating a variety of foods at each meal. As one review found:
“Habituation is slower when a variety of foods is presented. The effect of variety occurs for both low and high energy dense foods…which would lead to the dual recommendation that weight loss programs (1.) increase access to a variety of low energy density foods, to decrease habituation to them, and (2.) decrease access to a variety of high energy density foods, which would facilitate habituation to them” (Epstein LH et al. 2009).
Bottom line: we tend to regard some substances as addictive, others non-addictive. But the habituation response that leads addicts to seek ever greater amounts of a substance to achieve the same satisfying thrill actually plays out in many arenas for every human being. This happens especially in the realm of tastes, and even more in the realm of sweet tastes.
So experiment with sweet-free days – or, dare we suggest, a week? – and enjoy a variety of foods at every meal. You are likely to regain the pleasure of fruit or dark chocolate to a degree you have not experienced in years, and to find the subtle sweetness in foods, perhaps even in shellfish or salmon, where you normally miss it.
Your refreshed neurotransmitter pathways will thank you.
Wang Q-P, Lin YQ, Lai M-L, et al. PGC1α Controls Sucrose Taste Sensitization in Drosophila. Cell Reports. 2020;31(1):107480. doi:10.1016/j.celrep.2020.03.044.
Do Fruit Flies Have Emotions? California Institute of Technology. https://www.caltech.edu/about/news/do-fruit-flies-have-emotions-46769. Accessed May 21, 2020.
Leterme A, Brun L, Dittmar A, Robin O. Autonomic nervous system responses to sweet taste: Evidence for habituation rather than pleasure. Physiology & Behavior. 2008;93(4-5):994-999. doi:10.1016/j.physbeh.2008.01.005.
Epstein LH, Temple JL, Roemmich JN, Bouton ME. Habituation as a determinant of human food intake. Psychological Review. 2009;116(2):384-407. doi:10.1037/a0015074.