Artificial sweeteners spark more intense brain activity than real sugar

Your brain may be able to tell the difference between a diet soda and a regular sugary drink, even if they taste exactly the same to you. New research suggests that artificial sweeteners trigger distinct and more intense electrical activity in the brain compared to natural sugar, even when the sweetness levels are identical. These findings were published recently in the journal Foods.

The human desire for sweet foods is innate and powerful. This evolutionary drive has led to a modern health crisis characterized by excessive sugar consumption. In response, the food industry has developed numerous sugar substitutes. These additives promise the sensory pleasure of sweetness without the caloric cost.

While these products are popular, scientists are still working to understand how the human body and brain react to them. Most research focuses on how these sweeteners affect metabolism or appetite hormones. Less is known about how the brain processes the actual sensation of tasting them.

Sensory perception is usually measured in two ways. The first is explicit measurement, which involves asking a person to describe what they are tasting. This method relies on the participant’s ability to articulate their experience. It can be unreliable because people have different vocabularies and subjective baselines for sweetness. The second method is implicit measurement. This approach looks at physiological data that the participant cannot control. It offers a window into the body’s automatic reactions.

Xiaolei Wang and a team of researchers from Zhejiang University in China chose to use implicit measurement for this investigation. They utilized electroencephalography, commonly known as EEG. An EEG is a non-invasive test that records electrical patterns in the brain. It involves placing a cap with small metal discs called electrodes on a person’s scalp. These electrodes detect the tiny electrical charges that result from the activity of brain cells. This technology allows scientists to observe brain activity with millisecond-level precision.

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The researchers recruited 30 healthy university students for the experiment. All participants were right-handed and between the ages of 18 and 30. They had no history of smoking or alcohol consumption that might dull their sense of taste. Two participants were later excluded from the data because of excessive movement or eye blinking, which creates noise in the EEG signal. This left a final group of 28 participants.

The study aimed to answer two specific questions regarding sweetness. First, the team wanted to see how the brain reacts to different amounts of the same sweetener. Second, they wanted to see if the brain reacts differently to chemically distinct sweeteners that have been balanced to taste equally sweet. This condition is known as being “iso-sweet.”

To test the first question, the researchers prepared solutions of sucrose, which is common table sugar. They created four different concentrations: 1%, 3%, 5%, and 7%. Sucrose served as the baseline for natural sweetness.

To test the second question, the researchers selected three popular non-nutritive sweeteners. Non-nutritive sweeteners are substances that provide sweetness but few or no calories. The team used erythritol, sucralose, and stevioside. They carefully adjusted the concentration of these three solutions so that human tasters would perceive them as having the same sweetness intensity as the 7% sucrose solution.

The experiment took place in a quiet, temperature-controlled laboratory. Participants sat wearing the EEG caps and followed a strict “sip and hold” protocol. For each trial, the participant rinsed their mouth with water. They then received a 5 milliliter sample of a sweet solution. They held the liquid in their mouths without swallowing for five seconds. After this period, they spat the sample out and rinsed again. There was a 60-second rest period between each taste test to allow the brain signals to return to a neutral baseline.

The results regarding the concentration of sugar were unexpected. One might assume that a stronger concentration of sugar would produce a stronger electrical signal in the brain. The data showed the opposite effect. The 1% sucrose solution elicited a stronger EEG signal than the 5% or 7% solutions.

The researchers propose that this decrease in signal strength may be due to neural adaptation. When a stimulus becomes too strong, the brain sometimes dampens its response to avoid being overwhelmed. This is a phenomenon often seen in sensory processing, where the system becomes saturated. The brain essentially turns down the volume on the incoming “loud” taste signal.

The results regarding the different types of sweeteners were equally revealing. All three non-nutritive sweeteners produced stronger brain responses than the 7% sucrose solution they were designed to mimic. Even though a person might say the stevioside solution tasted just as sweet as the sugar solution, their brain activity told a different story.

Stevioside elicited the most robust neural response of all the substances tested. Erythritol caused the second strongest reaction. Sucralose also triggered a response that was statistically distinct from sugar. This indicates that the brain can differentiate between the chemical nature of sweeteners. It perceives them as different stimuli even if the conscious mind perceives the same level of sweetness.

The researchers also analyzed specific types of brain waves. They looked at alpha waves, which are typically associated with wakeful relaxation. They also analyzed delta waves. The non-nutritive sweeteners caused a surge in power in both these frequency bands. This suggests that artificial sweeteners might engage more neural resources than natural sugar.

The study also mapped where this activity was happening in the brain. The most active areas were the frontal and parietal-occipital regions. The frontal region is often involved in emotional regulation and decision-making. The parietal-occipital region, located toward the back of the head, is heavily involved in processing sensory information.

The timing of the brain’s reaction also varied by sweetener. The response to stevioside began early and remained strong throughout the tasting period. In contrast, the responses to erythritol and sucralose peaked and then faded relatively quickly. The response to natural sugar was slower to start and weaker overall.

These findings suggest that artificial sweeteners stimulate the brain in a way that is fundamentally different from sugar. The increased electrical activity might reflect the brain trying to process a chemical structure that does not perfectly match the biological expectation of “sweet energy.” The mismatch between the sweet taste and the lack of calories is a known area of interest in nutrition science.

There are limitations to this study that affect how the results should be interpreted. The sample size was relatively small. The participants were all young university students, so the results may not apply to older adults or children. Additionally, the participants did not swallow the solutions. Swallowing engages additional sensory receptors in the throat and digestive system that contribute to the overall experience of eating.

The researchers note that this technology could have practical applications. Food scientists could use EEG to objectively measure how consumers respond to new products. This would reduce the reliance on subjective taste tests. Understanding the neural “fingerprint” of different sweeteners could help companies design low-sugar foods that mimic the brain response of real sugar more closely.

Future research will likely explore these differences further. Scientists may look at how these brain responses correlate with feelings of satisfaction or cravings. They might also investigate if the brain learns to process these sweeteners differently over time with regular consumption. For now, the study provides evidence that to the human brain, sugar is not just a taste. It is a specific chemical signal that substitutes have yet to perfectly replicate.

The study, “EEG-Based Analysis of Neural Responses to Sweeteners: Effects of Type and Concentration,” was authored by Xiaolei Wang, Guangnan Wang, and Donghong Liu.