A bitter taste is usually seen as a signal of potential toxins, but some bitter substances are actually safe and even beneficial. For example, certain peptides and amino acids may taste bitter despite being non-toxic, nutritious, and even essential for human health. An innovative study sheds light on this puzzling occurrence.
Our taste buds play a crucial role in guiding our food choices. Among the five primary tastes, sweet and umami indicate a high-energy and nutritious content in food. Salt helps maintain our electrolyte balance, while sour tastes can signal unripeness or spoilage, and bitter tastes may warn against potential toxins.
Given the presence of toxic compounds in plants like strychnine and hydrogen cyanide, the aversion to bitterness seems rational. This aversion is especially pronounced in infants and young children, as even small doses of toxins can be harmful to them.
Protein Fragments: Bitterness and Nutrition
However, not all bitter-tasting substances are harmful but can, in fact, be nutritious. An interdisciplinary research team led by molecular biologist Maik Behrens has delved into the reasons behind this apparent contradiction.
The team from the Leibniz Institute found that five out of the approximately 25 human bitter taste receptors respond to free amino acids, peptides, and bile acids. Amino acids and peptides are breakdown products of proteins found abundantly in fermented foods like cheese and protein shakes, while bile acids serve various bodily functions.
Insight into Structural Similarities
“Interestingly, our modeling experiments reveal that a specific bitter-tasting peptide can mimic the 3D structure of bile acids in the receptor binding site. This accidental similarity might explain why these bitter taste receptors respond to both types of substances,” explains bioinformatician Antonella Di Pizio.
Lead author Silvia Schäfer notes, “Our genetic analyses demonstrate that the ability to detect both bile acids and peptides is highly conserved in three of the bitter taste receptor types and can be traced back to amphibians, indicating the importance of recognizing at least one of these substance groups across species.”
This study underlines the potential broader roles of bitter taste receptors in human health beyond food selection, presenting new insights into taste perception systems.
Further Information
Amino acids and peptides: Building blocks of proteins released during the protein breakdown process. Essential amino acids must be obtained from the diet.
Bile acids: Produced in the liver from cholesterol derivatives, bile acids aid in fat digestion.
Bitter receptors: Responsible for perceiving bitter tastes, around 25 types of bitter taste receptors are present in humans, not just in the mouth but also in various organs. Studies hint at their potential roles in immune responses, respiratory health, and metabolic regulation.
