How Fat Became the “Sixth Taste”

Mediterranean salad.
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It’s been craved. It’s been feared. Now, fat is taking on a new role. Recent research says fat joins the ranks of salty, sweet, sour, bitter and umami as the “sixth taste” detected during a dining experience.

By definition, “taste” is the sensory impression created after a food or other substance is consumed. To fit the criteria, taste buds must be able to pinpoint specific interactions that take place after certain molecules or ions make contact with receptors located on the tongue. A chain reaction takes place, as the receptor finds a pathway to the brain where it recognizes and distinguished a specific taste.

Let’s use sweetness to explain what happens. The taste of sweet is produced by the presence of sugar (the stimulant). When eaten, various G protein-coupled receptors on our taste buds recognize and receive the specific taste of the sugar. When two or more taste bud receptors are activated, the signal gets sent to the brain where it then recognizes the taste with its own receptors. The brain then recognizes the taste, often finding it to have desirable traits.

Testing for the Taste of Fat

There is no dispute that fat has an evident mouthfeel. A high-fat containing food, such as butter, has the ability to create a favorable, rich texture when used as an ingredient in a recipe. Think of the flakiness of a pie crust made with lard or the smoothness of a cream-based soup. However, the initial revelation of fat joining the ranks of other tastes did not come without controversy. Some scientists felt the claim was premature, and that fat is missing necessary traits in order to classify it as a true “taste.”

Researchers at Purdue University, led by Richard Mattes, PhD, tested fat’s taste by manipulating the nutrient and altering its natural state. In their first experiment, 100 willing participants were given isolated solutions containing the six tastes. Certain tastes – sweet, sour and salty — were easily identified. Participants had more difficulty deciphering the difference between the remaining three: bitter, umami and fat. This was believed to be because these flavors are known for their “strange” or “bad” tastes. Rather than separating each flavor, subjects likely grouped them as “unappealing.”

To address the ambiguousness of the results, another experiment was done solely looking at the bitter, umami and fat tastes. Once again, the tastes were divided into separate solutions. This time, disparities were clearly noted. Because it held flavor characteristics that do not overlap with the previously identified tastes, this finding was important for fat’s case as a separate taste.

So What Does Fat Taste Like?

Ironically, fat’s taste is not as decadent as one might assume.

The newly identified flavor — known as “oleogustus,” which is Latin for “taste for fat” — is likened to sampling a food that has gone rancid. Similar to bitter, fat is used as a warning to our gustatory system, telling the body to start limiting consumption when too much is eaten. However, when present in smaller doses, fat can add a desirable quality to a food, much like how a touch of bitterness livens a piece of dark chocolate or glass of wine.

For the world of science, the finding is a breakthrough, as researchers continue to discover new information about how flavors in food impact our senses. For health purposes, identifying fat as a taste could eventually help combat increasing rates of obesity. The hope is that new products could be developed that use healthier alternatives to favorite high-fat dishes, without the adverse side effects of previous fat alternatives.

With the unveiling of fat as the newest, distinguishable taste, the question now becomes, what’s the “seventh taste”? Other flavors that have been on researchers’ radars — and even competed with fat for the “sixth taste” title — include calcium, kokumi, piquance, coolness, metallicity and carbon dioxide. Time will tell if they meet the criteria as unknown taste bud receptors and neural pathways are found. While the gustatory realm awaits new discoveries, foodies everywhere can continue to savor the tried and true favorites: sweet, salty, sour, bitter, umami and, now, oleogustus.

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Bethany Oxender
Bethany Oxender, MS, RDN, is a clinical dietitian based in Ann Arbor, MI, specializing in weight management. Follow her on Twitter or Instagram and read her blog, Bethany Grey.