For many years, scientists agreed that human tongues perceived four basic tastes: sweet, sour, salty and bitter. Then in 2002, receptors were confirmed for a taste called umami — first proposed by a Japanese chemist in 1908 and commonly described as meatiness or savoriness — and it became widely accepted as the fifth basic taste.
Since then, molecular biologists have theorized that humans may have as many as 20 distinct receptors for such tastes as calcium, carbonation, starch and even water. The data supporting each vary widely, but one contender for a sixth taste has begun to stand out from the rest: fat.
Currently, the debate is still over whether fat is a taste, and studies are increasingly likely to say that it is.
In 2010, for example, researchers at Deakin University in Australia found that people were able to detect the taste of fatty acids. This year, researchers at the Center for Human Nutrition at Washington University School of Medicine in St. Louis said they had discovered that some people may be more sensitive to the presence of fat in foods than others.
For the latter study, published in March in the Journal of Lipid Research, 21 people with a body mass index of 30 or more — considered clinically obese — tasted three solutions with a similarly viscous texture and were asked to identify the one that was different.
One of the solutions contained a bit of fatty oil. Participants whose bodies produce more of a protein called CD36 more often picked that solution out of the lineup, suggesting that they were more sensitive to the fatty acids.
Researchers speculated that this CD36 protein made people more sensitive to the taste of fat, so they perceive it in smaller amounts. If true, that would suggest a genetic basis for why some people crave fat more than others.
“The take-home message is that we now know there is a fat-taste component, and we cannot dismiss it. It exists in humans, but how it influences behavior and fat intake, we still don’t know,” said Nada Abumrad, one of the authors of the study and the Atkins Professor of Medicine and Obesity Research at Washington University in St. Louis.
Traditionally, scientists have viewed fat as something humans detect through texture or aroma rather than taste.
To understand this better, a little familiarity with food science is helpful: In this context, taste refers to what we perceive through the tongue alone. Flavor refers to what we perceive through both taste and smell. For example, to the tongue alone, ice cream mainly tastes sweet. It’s not until the nose gets involved that you can experience the flavors — chocolate or strawberry, for example. This also explains why foods you don’t enjoy might go down more easily if you pinch your nose, or why your dinner is less enjoyable when your sinuses are congested during a cold.