Bitter foods aren’t always harmful, study explains

Your sense of taste is essential for making food choices. Among the five basic tastes, sweet and umami indicate energy-rich and nutritious foods. Salt helps maintain electrolyte balance, while sour flavors can warn of unripe or spoiled food, and bitter ones can signal potentially toxic substances.

Given the numerous toxic plant substances, like strychnine from nux vomica or hydrogen cyanide from manioc, this makes sense. It's also logical that babies and toddlers reject bitter foods since even small amounts of these toxic substances can harm them.

However, not everything bitter is dangerous; some can be nutritious. An interdisciplinary research team led by molecular biologist Maik Behrens investigated this seemingly contradictory phenomenon for the first time.

Using a cellular test system, the team discovered that five of the approximately 25 human bitter taste receptor types react to free amino acids and peptides, as well as bile acids. Free amino acids and peptides are produced during protein breakdown and are abundant in fermented foods like cream cheese and protein shakes. While bile acids play virtually no role as food components, they fulfill essential functions in the body and could activate endogenous bitter receptors found on intestinal and blood cells.

“Interestingly, our modeling experiments show that a certain bitter-tasting peptide can adopt a functionally active 3D shape similar to that of bile acids inside the receptor binding pocket. This coincidental similarity could explain why the same set of the bitter taste receptors react to both groups of substances," explains bioinformatician Antonella Di Pizio.

First author Silvia Schäfer adds: "Our genetic analyses also show that the ability to recognize both bile acids and peptides is highly conserved in three of the bitter taste receptor types and can be traced back to amphibians. This again indicates that at least the recognition of one of the two substance groups is important across species."

"Bile acids and bitter taste receptors existed millions of years before the typical bitter substances of today's flowering plants and long before humans - in fish, for example. This supports the hypothesis that bitter taste receptors originally also regulated important physiological processes and not just warned against toxic substances," explains principal investigator Maik Behrens. "Our findings provide new insights into the complex systems of taste perception and suggest that bitter receptors play additional, as yet unknown roles in human health that go beyond their function in food selection."

This research shows that while bitter taste often signals danger, it can also indicate nutritious elements. Your understanding of taste and its roles in human health continues to evolve, revealing complex interactions that go beyond simple food selection.

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