Umami is one of the five basic tastes, along with sweet, sour, bitter, and salty. It is described as a savory, meaty, or brothy taste. Umami is common in foods like meat, fish, cheeses, tomatoes, mushrooms, soy sauce, and broths. Humans have taste receptors specifically for detecting umami flavors. But can animals other than humans also taste umami?
Which animals have been shown to taste umami?
Several studies have demonstrated that animals besides humans can detect and have preferences for umami tastes. Animals that appear to be able to taste umami include:
- Rodents: Studies have shown that mice and rats are attracted to umami solutions and have specific umami taste receptors that respond to umami flavors.
- Cats: Cats have been shown to respond to and prefer solutions with monosodium glutamate (MSG), one of the main sources of umami taste.
- Dogs: While less research has been done in dogs, there is evidence they can detect glutamate, an umami compound.
- Birds: Taste receptor genes similar to umami receptors in humans have been found in chickens and zebra finches.
- Fish: Some studies on fish like catfish and trout indicate they may be able to sense umami compounds through taste receptors.
- Insects: The fungus gnat has been shown to be attracted to umami solutions.
So while the sense of umami may not be universal among all animal species, the evidence so far shows that the ability to taste umami is certainly not limited to just humans. A wide variety of vertebrate and invertebrate animals appear able to detect this savory taste.
How do we know other animals can taste umami?
Researchers have used several approaches to demonstrate that animals can sense umami flavors:
Behavioral Studies
In behavioral studies, animals are given different solutions containing umami compounds and their reactions observed. For example, rats and mice will readily drink solutions containing MSG but avoid bitter or sour solutions. Cats will respond more positively to MSG solutions compared to plain water. These preferences indicate the animals can taste and enjoy the umami flavor.
Nerve Recordings
Measuring activity from nerves that innervate taste buds can also reveal umami detection. When umami compounds are applied to the tongue, specific patterns of nerve signals are produced. Researchers have recorded these distinctive signals in rodents, fish, and frogs in response to umami, demonstrating there are umami-specific taste pathways in these species.
Molecular Studies
Studies have identified receptor proteins that specifically bind to umami compounds and trigger taste nerve signals in the mouth and brain. Variants of these umami taste receptors are found in species like mice, chickens, cats, and fish, indicating an evolutionary conservation of umami detecting biology across vertebrates.
Genetic Knockout
Deleting or disabling umami receptor genes in mice leaves them unable to detect umami compounds. This proves that those receptor genes are essential for umami taste. This kind of genetic knockout approach produces compelling evidence that umami taste depends on specific receptors in animals.
What is the purpose of umami taste for animals?
So why did umami tasting ability evolve in so many animal species? Detecting and enjoying umami flavors likely provides advantages for animal survival:
Identifying Protein-Rich Foods
Umami taste helps animals identify protein-rich foods. Most umami compounds come from amino acids that make up proteins. Sensing umami signals the presence of meat, cheese, fish, and other protein sources. Preferring umami helps animals seek out these nutritious, protein-containing foods.
Signaling Nutritional Abundance
Umami compounds like glutamate are most abundant in foods ripe for harvest or capture. For example, glutamate levels in tomatoes and mushroom spike as they fully ripen. High levels of inosinate arise in aged meat. For predators, the umami taste may signal prey animals with higher nutrient stores. So umami provides useful information about food quality and availability.
Aiding Digestion
When animals taste savory umami foods, it stimulates their digestive system in preparation for a protein meal. Salivation and gastric acid secretion increases, speeding up digestion of amino acids. So umami directly helps animals efficiently process protein-rich nutrients.
Evaluating Freshness
Some umami compounds increase with aging and decay as proteins break down. The umami taste may help animals determine if food is fresh by the relative amounts of different umami chemicals. Ripe/aged foods have higher levels of umami and taste appealing, while rotten foods are too far degraded.
Adding Flavor Enjoyment
While the nutritious value of umami is important, animals appear to simply enjoy the sensation of its savory taste. The umami flavor makes food more palatable, encouraging animals to eat and favor protein-rich foods.
How do animal umami receptors compare to human receptors?
The main umami taste receptors in humans belong to the TAS1R family of proteins. TAS1R1 and TAS1R3 join together to form a receptor that specifically binds to umami compounds like glutamate. Animals also have variants of the TAS1R receptor genes that allow them to detect umami:
| Animal | Umami Receptor |
|---|---|
| Mouse | Tas1r1 + Tas1r3 |
| Cat | Tas1r1 + Tas1r3 |
| Dog | Tas1r1 + Tas1r3 |
| Chicken | Tas1r1 + Tas1r3 |
| Zebrafish | Tas1r1 + Tas1r3b |
| Bullfrog | Tas1r1 + Tas1r3 |
The components are similar to the human umami receptors, except some species like zebrafish have a slightly different variant of TAS1R3. But the basic combination of TAS1R1 and TAS1R3 to form umami receptors appears conserved across many animal groups. This suggests these receptor genes evolved long ago in a common ancestor and have been maintained by natural selection.
Are there any animals that cannot taste umami?
While umami sensing appears common for mammals, birds, reptiles, amphibians, and fish, not all animals necessarily share this ability. For example:
- Dogs may have a reduced umami sense compared to humans. They have mutations that may impair their TAS1R receptors.
- Insects like flies do not have TAS1R genes, instead using other molecular pathways to detect amino acids and protein sources.
- It is unknown if invertebrates like worms or mollusks can taste umami, though they do respond to amino acid stimuli.
- Not enough study has been done on the umami tasting abilities of animals like marsupials, monotremes, and aquatic mammals.
So while the ability to taste umami is widespread, it may not be truly universal among all animal species. Some groups like the insects appear to use different mechanisms. There are also likely some species that do not detect umami at all if it was not useful in their ecological niche. But any animal that consumes nutrients from other living things would benefit from umami taste, so this ability evolved readily in many species.
Conclusion
In summary, there is strong evidence from behavioral, physiological, genetic, and evolutionary studies that many animals besides humans can taste and appreciate umami flavors. Mice, rats, cats, dogs, fish, amphibians, reptiles, and birds have all shown the ability to detect umami compounds using receptors similar to humans. Sensing umami provides valuable information about protein-rich food sources and stimulates digestion. This powerful flavor cue likely evolved in diverse animal species because it aids survival. However, some invertebrates appear to use different mechanisms to sense amino acids. And there are likely some specialized species that do not perceive umami at all if it did not suit their ecological context. But while not universal, umami detection is certainly widespread across the animal kingdom, driving attraction to protein-rich foods.