Milk addition to coffee may exert anti-inflammatory effect: Study

Denmark: Adding a dash of milk to a cup of coffee can have anti-inflammatory effects, a recent study from the University of Copenhagen has shown. The study appeared in the Journal of Agricultural and Food Chemistry on January 30, 2023. 

The study investigated how polyphenols behave when combined with amino acids, the building blocks of proteins. The results have been promising.

Is it not amazing that something as simple as a cup of coffee with milk has an anti-inflammatory effect in humans? A combination of proteins and antioxidants doubles the anti-inflammatory properties in immune cells. The researchers hope to be able to study the health effects on humans.

Whenever bacteria, viruses and other foreign substances enter the body, our immune systems react by deploying white blood cells and chemical substances to protect us. This reaction, commonly known as inflammation, also occurs whenever we overload tendons and muscles and is characteristic of diseases like rheumatoid arthritis.

Antioxidants known as polyphenols are found in humans, plants, fruits and vegetables. The food industry also uses this group of antioxidants to slow the oxidation and deterioration of food quality and thereby avoid off flavours and rancidity. Polyphenols are also known to be healthy for humans, as they help reduce oxidative stress in the body, giving rise to inflammation.

But much remains unknown about polyphenols. Relatively few studies have investigated what happens when polyphenols react with other molecules, such as proteins mixed into foods that we then consume.

In a new study, researchers at the Department of Food Science, in collaboration with researchers from the Department of Veterinary and Animal Sciences, at University of Copenhagen investigated how polyphenols behave when combined with amino acids, the building blocks of proteins. The results have been promising.

"The study shows that as a polyphenol reacts with an amino acid, its inhibitory effect on inflammation in immune cells is enhanced. As such, it is clearly imaginable that this cocktail could also have a beneficial effect on inflammation in humans. 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," says Professor Marianne Nissen Lund from the Department of Food Science, who headed the study.

Twice as good at fighting inflammation

To investigate the anti-inflammatory effect of combining polyphenols with proteins, the researchers applied artificial inflammation to immune cells. Some of the cells received various doses of polyphenols that had reacted with an amino acid, while others only received polyphenols in the same doses. A control group received nothing.

The researchers observed that immune cells treated with the combination of polyphenols and amino acids were twice as effective at fighting inflammation as the cells to which only polyphenols were added.

"It is interesting to have now 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," says Associate Professor Andrew Williams of the Department of Veterinary and Animal Sciences at the Faculty of Health and Medical Sciences, who is also a senior author of the study.

Found in coffee with milk

Previous studies by researchers demonstrated that polyphenols bind to proteins in meat products, milk and beer. Another new study 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.

"Our result demonstrates that the reaction between polyphenols and proteins also happens in some coffee drinks with milk that we studied. The reaction happens so quickly that it has been difficult to avoid in any of the foods we've studied so far," says Marianne Nissen Lund.

Therefore, the researcher does not find it difficult to imagine that the reaction and potentially beneficial anti-inflammatory effect also occur when other foods consisting of proteins and fruits or vegetables are combined.

"I can imagine that something similar happens in, for example, a meat dish with vegetables or a smoothie if you make sure to add some protein like milk or yogurt," says Marianne Nissen Lund.

Industry and the research community have noted the major advantages of polyphenols. As such, they are working on adding the right quantities of polyphenols in foods to achieve the best quality. The new research results are promising in this context as well:

"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," explains Marianne Nissen Lund.

Polyphenol Facts

• Polyphenols are a group of naturally occurring antioxidants important for humans.

• They prevent and delay the oxidation of healthy chemical substances and organs in our bodies, thereby protecting them from damage or destruction.

• Polyphenols are found in various fruits and vegetables, tea, coffee, red wine and beer.

• Due to their antioxidant properties, polyphenols are used in the food industry to minimize the oxidation of fats in particular and the quality deterioration of foods, to avoid off flavours and rancidity.

Reference:

Jingyuan Liu, Mahesha M. Poojary, Ling Zhu, Andrew R. Williams, Marianne N. Lund. Phenolic Acid–Amino Acid Adducts Exert Distinct Immunomodulatory Effects in Macrophages Compared to Parent Phenolic Acids. Journal of Agricultural and Food Chemistry, 2023;

DOI: 10.1021/acs.jafc.2c06658