A recent investigation has revealed that when the natural sweetener thaumatin is digested, bitter-tasting protein fragments (peptides) emerge in the stomach. In laboratory tests, these peptides successfully trigger acid production in human stomach cells and can affect inflammatory responses.
A new investigation led by the Leibniz Institute for Food Systems Biology at the Technical University of Munich has discovered for the first time that during the digestion of the natural sweetener thaumatin, bitter-tasting protein fragments (peptides) are created in the stomach. In a cellular testing environment, these peptides can boost acid secretion from human stomach cells and influence inflammatory processes. “Our research sheds light on the health implications of this plant protein, commonly used as a sweetener,” explains Veronika Somoza, the study’s lead researcher and director of the Leibniz Institute.
The research team, headed by Veronika Somoza, is examining how bitter-tasting food compounds affect the metabolism of stomach cells and overall health. They developed a human gastric cell line (HGT-1 cells) as a testing method. In previous research, the scientists demonstrated that specific bitter substances can engage the stomach cells’ own bitter taste receptors, leading to an increase in proton release and thereby boosting acid production within the cells. These bitter substances also include peptides formed during the breakdown of milk proteins.
Building on earlier research
“Public interest prominently centers on not just bitter compounds but also the health impacts of sweeteners. Given our prior findings, we sought to determine if bitter peptides also arise from the digestion of the sweet protein thaumatin, which could have physiological effects,” says Phil Richter, the primary author and doctoral researcher at the Leibniz Institute.
Through studies on pigs, laboratory experiments, and sensory evaluations, the team identified three bitter-tasting peptides created during the digestion of thaumatin in the stomach. In their testing environment, even extremely low concentrations of these bitter peptides (in the nanomolar range) prompted HGT-1 cells to release protons.
To understand the potential anti-inflammatory properties of these three peptides, the research team first assessed how the test system’s stomach cells reacted to the addition of Helicobacter pylori proteins. This bacterium can lead to inflammatory stomach diseases, including stomach cancer, and approximately half of the global population is infected with it. Uniquely, it can thrive in the highly acidic environment of the stomach by neutralizing stomach acid’s low pH level.
Anti-inflammatory properties
The findings revealed that Helicobacter pylori proteins caused a surge in pro-inflammatory interleukin 17A release from the test cells. “Interestingly, we observed that the gastric cells’ induced interleukin release could be decreased by up to 89.7 percent with the addition of one of the identified bitter peptides. The gastric cells’ own bitter taste receptor, TAS2R16, played a role in this anti-inflammatory response as well as in stimulating proton release,” discusses Phil Richter.
“The levels of peptides tested in our research reflect realistic concentrations achievable in the stomach through consumption of a typical sweetener tablet. Therefore, our results indicate that the anti-inflammatory potential of thaumatin or its bitter breakdown products, alongside the role of endogenous bitter taste receptors, needs further exploration. Our goal is to enhance understanding of the molecular mechanisms behind diet-related inflammatory gastric conditions, particularly regarding Helicobacter pylori infections,” clarifies Veronika Somoza.
About the study: This study was conducted by the Leibniz Institute for Food Systems Biology at the Technical University of Munich in collaboration with TUM and received funding from both institutions. Full results have been published in the journal Food Chemistry.
Thaumatin is a protein sourced from the Katemfe fruit, native to West Africa. It has been known for its sweetening abilities and enhances flavor. As an EU-approved sweetener (E 957), it’s commonly found in various foods and beverages. Due to its powerful sweetening capability, which is around 1,600 times sweeter than regular sugar, people consume it in minimal daily quantities, and its caloric contribution of approximately four kilocalories per gram is negligible. However, one limitation is that thaumatin loses its sweetness when exposed to heat from baking or cooking, although its flavor-enhancing properties remain intact.
No acceptable daily intake (ADI) level has been established for thaumatin since the body completely breaks it down, making even high consumption levels considered safe from a toxicological perspective. The ADI represents the maximum amount of a substance a person can safely ingest daily over a lifetime without adverse health effects.
One nanomole is a measure of one billionth (1/1,000,000,000) of a mole, indicating an extremely tiny quantity of a substance. One mole of any substance contains approximately 6 x 1023 particles.
Bitter taste receptors exist not only on the tongue but also on various tissues and cells, including the parietal cells of the stomach that produce stomach acid by secreting protons.
