When you visit a restaurant or coffee shop, the white packets of sweetener are table sugar, and the brown, raw sugar. Everything else is artificial: blue, aspartame; green, stevia; pink, saccharin; and yellow, sucralose.
Artificial sweeteners reduce net calories in the moment but may contribute to weight gain and other health impacts in the long-term.
In 1965, James M. Schlatter accidentally discovered the first example of the chemical we know as aspartame:
To pick up a paper, he had licked his finger. He tasted an unexpectedly sweet trace of a substance that had, he realized, earlier splashed onto the outside of a flask he had handled. It contained L-aspartyl-L-phenylalnine methyl ester.
Schlatter applied for a patent on 18 April 1966 (U.S. No. 3,492,131) for his employer, G.D. Searle & Co.; the US patent office assigned the patent on 27 Jan 1970. On 24 July 1981, the Food and Drug Administration initially approved aspartame as a food sweetener. In 1996 it extended that to a general-purpose sweetener where it had brand names such as Nutrasweet and Equal.
Saccharin became “the first widely commercialized non-nutritive sweetener” under the trade name Sweet’n Low (1957). The original weight-control product had been discovered accidentally in 1879, when Constantin Fahlberg “noticed a sweet taste on his hand.”
Originally, NutraSweet and Equal marketed aspartame as a competitor to Sweet’n Low. Today, NutraSweetM is based on stevia. Although Equal Original is still based on aspartame, Equal sells variations based on saccharin, stevia and sucralose. Splenda was the first to use sucralose, which was also discovered by accident.
Around World War II, in response to a sugar shortage and evolving cultural views of beauty, the target consumer group for noncaloric sweetener manufacturers shifted from primarily diabetics to anyone in the general public wishing to reduce sugar intake and lose weight. Foods containing artificial sweeteners changed their labels. Instead of cautioning ‘only for consumption by those who must restrict sugar intake’, they read for those who ‘desire to restrict‘ sugar.
The brain knows the difference
In the intervening decades, these products escaped the sugar container at the coffee shop. They are found in diet sodas, of course, but also in baby food, chewing gum, frozen dinners, vitamins and yogurt, to provide a non-exhaustive list.
Both saccharin and aspartame have been subject to concerns about causing cancer. FDA has cleared both.
The more urgent, but less popularly discussed, concern should be effects of artificial sugars on the reward system in the brain and effects on the brain-gut system.
In 2010, researchers noted that obesity in the United States correlated with “an increase in the widespread use of non-caloric artificial sweeteners, such as aspartame (e.g., Diet Coke) and sucralose (e.g., Pepsi One).”
Although many people who are not diabetic shift to artificial sweeteners to lose weight, the opposite is more likely to happen.
[By 2010,] several large scale prospective cohort studies [had] found positive correlation between artificial sweetener use and weight gain.
The hypothesis is how the brain’s food reward pathways work in the presence of artificial sweeteners.
Say you have a box of cupcakes. The initial bite is bliss. In that first taste, dopamine is released in the brain’s reward pathway and you get a jolt of pleasure. In addition to dopamine, the release of leptin, a hormone that regulates appetite and informs the brain when you are full, reduces activation of dopamine neurons in the midbrain, lowering the reward value of sugar. As a result, the second bite of the cupcake is less rewarding than the first and you begin to feel full with subsequent bites, hopefully stopping you from gorging yourself on the entire box of cupcakes.
Functional magnetic resonance imaging (fMRI) studies suggest that the “brain’s reward pathway is conditioned to prefer a sugar, or caloric-based, stimulus.”
That was from a research summary in Scientific American in 2013.
It’s important to contextualize “sugar.” It “encompasses a number of substances the human body uses as fuel.” Artificial sweeteners provide no fuel. But there’s more.
To determine how the brain’s preference for sugar develops, researchers are now studying the connections between the gut-to-brain circuit and other brain systems, like those involved in reward, feeding and emotions. Although the studies are in mice, Zuker believes that essentially the same glucose-sensing pathway exists in humans.
In 2018, researchers showed that only 14 days of substituting sucralose for sugar “showed a significant decrease in insulin sensitivity.” Insulin resistance can lead to adult-onset diabetes.
Researchers at Duke University reported in January 2022 that the important cells that encourage us to eat sugar are in the gut, not on the tongue. “Sugar has both taste and nutritive value and the gut is able to identify both.”
Despite decades of habitual consumption of artificial sweeteners — intentional and non-intentional — we have not, as a society, questioned long-term health impacts. Nor have we required corporations to track them.