Why do people love sweet foods and drinks?
Over many millennia, humans who found and favored foods high in readily available calories tended to survive and pass on their genes.
The great challenges of prehistoric man's search for food, water, and shelter demanded reliable fuel for the muscles and brain … for which only sugar will suffice.
Sugary, starchy foods provide glucose, which the body circulates in the blood for immediate needs, and stores in cells.
As a “backup” supply to enable greater physical and mental endurance, the body also stores glucose in muscle cells and in certain brain cells, within a starch called glycogen.
Naturally, the best choices for energizing “fuels” were and remain foods higher in sugars (e.g., fruits, grains, tubers, and root vegetables).
Foods high in fats (e.g., nuts, seeds, fatty meats and fish) come in second.
In a pinch, certain fats stored in the body (e.g, triglycerides) can be burned to provide energy ... but they can't substitute for dietary sugars and starches (complex sugars).
The high-protein foods available to prehistoric humans – mostly lean wild meats and shoreline shellfish – enable muscle-growth and more, but lack sufficient fats or sugars to provide quick energy.
A survival instinct became a disadvantage
Today, “calorie-dense” fatty and sugary foods abound at cheap prices, even in many non-affluent countries.
This historically recent bounty turned the age-old preference for sugary, fatty foods into a main driver of modern metabolic disorders … obesity, diabetes, and cardiovascular disease.
Cravings for sugary foods, whether natural (fruits) or manmade (cake) are driven by the amount of energy (calories) they provide.
This explains why the brain's reward centers get more satisfaction from real sugars, versus artificial sweeteners.
Our deep-rooted, evolution-driven love of foods high in fat and sugar drives the growing global epidemic of obesity and diabetes.
Fake sugars were intended to fight fat gain
Decades ago, food companies began using artificial sweeteners to meet consumer demand for low-calorie fare to help control their weight and/or fight diabetes.
Most of the many prior studies suggest that while artificial sweeteners don't help people lose weight, they don't necessarily lead to weight gain, either.
But exceptions can be found in the medical literature.
It's well established that animals and people alike get more pleasure and “reward” from real sugars, versus non-caloric artificial sweeteners.
And the results of a new study imply that it's hard to fool the brain by providing it with no-calorie, energy-free sweeteners.
Fake sweets didn't curb rodent's sugar cravings
Professor Ivan de Araujo of the Yale University School of Medicine led a study testing the effects of artificially sweetened drinks on rodents' cravings, versus sugary drinks (Tellez LA et al. 2013).
They performed behavioral tests involving sweeteners and sugars, while measuring chemical responses in brain circuits for reward.
Based on the known similarities in how rodents and humans respond to dietary sugars, the researchers believe the findings are likely to apply to people.
As they said, their findings imply that people who habitually consume low-calorie foods and/or drinks while hungry may be more likely to “relapse” and choose sugary, high-calorie foods in the near future.
Dr. Araujo proposed adding a bit of real sugar to forestall this effect: “The results suggest that a ‘happy medium' could be a solution; combining sweeteners with minimal amounts of sugar so that energy metabolism doesn't drop, while caloric intake is kept to a minimum.” (YUSM 2013)
Of course, that proposal presumes no fear for the possible ill effects of ingesting artificial sweeteners – especially much-maligned aspartame – on a regular basis.
The study identified a specific chemical signal critical to determining the brain's choice between sugars and sweeteners.
This chemical signal regulates levels of dopamine – the brain's own rewarding, pleasure-making “drug” – by talking to dopamine-producing cells.
Importantly, that signal only orders release of dopamine when the body breaks sugar down into a form (glucose) usable as fuel for its cells.
As Professor de Araujo said, “…when hungry mice are given a choice between artificial sweeteners and sugars, they are more likely to switch their preferences towards sugars, even if the artificial sweetener is much sweeter than the sugar solution.” (YUSM 2013)
The team now hopes to identify the cell receptors and pathways in the brain associated with the rewarding effects of sugar, to help reveal solutions to cravings.
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- Tellez LA, Ren X, Han W, Medina S, Ferreira J, Yeckel C, de Araujo IE. Glucose Utilization Rates Regulate Intake Levels of Artificial Sweeteners. J Physiol. 2013 Sep 23. [Epub ahead of print]
- Yale University School of Medicine (YUSM). The brain cannot be fooled by artificial sweeteners. September 22, 2013