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Stimulate our digestion: bitter substances in coffee can regulate gastric acid production


Bitter receptors in the mouth: caffeine can regulate gastric acid production
Many people opt for coffee or bitter after a long meal. After all, such drinks are said to help stimulate digestion. However, many doubt that this really helps. However, researchers have now found that the bitter substance caffeine can have an effect on gastric acid production and thus on digestion.

Folk wisdom about digestion
Some people try to stimulate digestion with a cigarette after eating. Others think that schnapps in particular provides help here. It is also common to drink an espresso or other coffee after a meal. According to experts, many folk wisdoms about digestion are wrong. An international team of researchers has now found that caffeine can affect gastric acid production.

Caffeine can regulate gastric acid release
The stimulating bitter caffeine can both stimulate and delay the release of hydrochloric acid in the stomach, depending on whether it activates bitter receptors in the stomach or in the mouth.

“As our results show, bitter receptors generally play a role in regulating gastric acid release. It would therefore be conceivable that bitter substances or bitter blockers could in future be used as therapeutic agents to treat gastric acidity, ”study leader Veronika Somoza from the University of Vienna said in a statement.

The team led by nutrition physiologist Somoza and first author Kathrin Liszt from the Faculty of Chemistry at the University of Vienna, which includes researchers from the German Institute for Nutritional Research (DIfE), Jakob Ley from Symrise AG in Holzminden and scientists from the Blizard Institute London his results now in the journal "PNAS".

What was known at the beginning of the study
Caffeine not only stimulates the central nervous system and increases blood pressure, but also stimulates the release of stomach acid.

Recent studies also indicate that, in addition to caffeine, other bitter substances, for example from hops, also stimulate acid production in the stomach. The mechanisms by which this happens have not yet been sufficiently researched.

It is also known that humans perceive bitter substances via around 25 different types of bitter receptors, which are located on the tips of the taste receptor cells in the mouth and throat and are intended to warn against swallowing toxic substances.

Five of them react to caffeine, among other things. Studies have recently started to show that taste receptors for bitterness can also be found in other places in the digestive system, for example in the stomach. The function of the receptors there is largely unknown and also little research has been done.

Half an hour after taking caffeine increased release of gastric acid
Since the existing facts suggest that caffeine affects gastric acid release via bitter receptors in the mouth and stomach, the scientists in the current study looked into the question of whether such a connection actually exists.

For this purpose, pH measurements in the stomach were carried out in healthy female and male study participants.

The researchers also used human tissue samples from the stomach and an established cellular model system (HGT-1 cells) to study gastric acid release in order to be able to check the connection at the cellular and molecular level.

If the study participants took 150 mg of caffeine encapsulated in the form of a pill that only dissolved in the stomach, this led to an increased release of stomach acid after about 30 minutes.

If, on the other hand, the participants received a corresponding caffeine solution, which stimulated not only the receptors in the stomach but also the bitter receptors in the oral cavity, the gastric acid release was delayed.

The perceived bitterness of the caffeine correlated with the amount of gastric acid released. In addition, the researchers detected bitter receptors that react to caffeine both in human tissue samples of the stomach and in the HGT-1 cells.

Using the model system of the HGT-1 cells, they also showed that the bitter receptor TAS2R43 is at least one of the receptors through which caffeine regulates gastric acid release. Switching off the TAS2R43 receptor at the gene level (knock out model) additionally confirmed this result.

The stimulating effect could be reduced by adding homoeriodictyol, a bitter blocker that also inhibits TAS2R43. Tests subsequently carried out with study participants, in which the subjects took the bitter blocker together with caffeine, also led to a reduction in the caffeine effects.

Conclusion and outlook
"Although in many cultures after eating a glass of bitter bitters or coffee is used to counter digestive problems, we still know surprisingly little about the molecular interplay between bitter substances and the digestive system," said Veronika Somoza from the Institute of Nutritional Physiology and Physiological Chemistry the University of Vienna.

“In the future, clarifying these relationships could help to develop new therapeutic agents against reflux disease or gastric ulcers,” the professor continued.

"In any case, our results are promising and prove that bitter receptors are involved in the regulation of digestive processes in addition to their function as taste sensors," added co-author Wolfgang Meyerhof from DIfE.

"Research into the bitter receptors, which we have already detected in the intestine, heart muscle and thyroid cells, not only reveals completely new perspectives and starting points in this context, which we want to pursue with our cooperation partners in the future," said DIfE- Finally, taste researcher Maik Behrens. (ad)

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