Caffeic acid (CA) and chlorogenic acid (CGA) are commonly found in phenolic acids in plant-derived foods and beverages. Their corresponding adducts with cysteine (Cys) have been detected in coffee-containing beverages. However, despite the well-documented antioxidant and anti-inflammatory activity of CA and CGA, the immunomodulatory activities of the Cys adducts are unknown.
According to a new study from the University of Copenhagen, a cup of coffee with milk has an anti-inflammatory effect in humans. That happens because a combination of proteins and antioxidants doubles the anti-inflammatory properties in immune cells.
Antioxidants known as polyphenols are found in humans, plants, fruits, and vegetables. Polyphenols are also known to be healthy for humans, as they help reduce oxidative stress in the body, giving rise to inflammation.
But there is still a lot to learn about polyphenols. Only a small number of research have looked into how polyphenols interact with other molecules, including the proteins added to the meals we eat.
Scientists from the University of Copenhagen’s Department of Food Science and the Department of Veterinary and Animal Sciences worked together on a recent study to examine how polyphenols interact with amino acids, which are the building blocks of proteins. The outcomes are encouraging.
Professor Marianne Nissen Lund from the Department of Food Science, who headed the study, said, “In the study, we show that as a polyphenol reacts with an amino acid, its inhibitory effect on inflammation in immune cells is enhanced. As such, it is imaginable that this cocktail could also have a beneficial effect on human inflammation. We will now investigate further, initially in animals. After that, we hope to receive research funding which will allow us to study the effect in humans.”
The scientists deliberately inflamed immune cells to test if polyphenols and proteins have an anti-inflammatory impact. While some cells just received polyphenols in the same amounts, some cells received different doses of polyphenols that had interacted with an amino acid. A control group did not get anything.
The scientists found that adding polyphenols and amino acids to immune cells doubled their ability to reduce inflammation compared to cells that received polyphenols.
Associate Professor Andrew Williams of the Department of Veterinary and Animal Sciences at the Faculty of Health and Medical Sciences said, “It is interesting to have observed the anti-inflammatory effect in cell experiments. And obviously, this has only made us more interested in understanding these health effects in greater detail. So, the next step will be to study the effects in animals.”
In another study, scientists tested whether the molecules also bind to each other in a coffee drink with milk. Indeed, coffee beans are filled with polyphenols, while milk is rich in proteins.
The result shows the reaction between polyphenols and proteins also happens in some of the coffee drinks with milk that we studied. Because the reaction occurs so quickly, it has been challenging to prevent it in any of the meals that we have thus far tested.
Therefore, it is not difficult for scientists to think that the reaction and beneficial anti-inflammatory impact also occur when other foods consisting of proteins and fruits or vegetables are mixed.
“Because humans do not absorb that much polyphenol, many researchers are studying how to encapsulate polyphenols in protein structures which improve their absorption in the body. This strategy has the added advantage of enhancing the anti-inflammatory effects of polyphenols.”
- Jingyuan Liu, Mahesha M. Poojary et al. Phenolic Acid–Amino Acid Adducts Exert Distinct Immunomodulatory Effects in Macrophages Compared to Parent Phenolic Acids. American Chemical Society. DOI: 10.1021/acs.jafc.2c06658
- Mahesha M. Poojary et al. Covalent bonding between polyphenols and proteins: Synthesis of caffeic acid-cysteine and chlorogenic acid-cysteine adducts and their quantification in dairy beverages. Food Chemistry. DOI: 10.1016/j.foodchem.2022.134406