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How do Humans Taste Spice?

Updated: Aug 3, 2021

Author: Ellie Wang

Editors: Vincent Chang and Liane Xu

Artist: Denise Suárez

Of all the mammals living on this planet, humans and tree shrews are the only two that enjoy eating spicy foods. The reason why we like spice is a question for another day. What’s answered here is how humans taste the spice and what measurements quantify it.

Despite the term “tasting spice”, our taste buds aren’t the structures that detect capsaicin, the chemical compound that causes the hot feeling of spicy foods. The tongue, mouth, and throat contain Transient Receptor Potential Vanilloid subtype 1, or TRPV1. This ion channel is found in sensory neurons throughout our body for detecting temperatures above 42 degrees Celsius and harmful acid. Once it does, it sends signals to the brain, leading to a painfully hot sensation. By binding to TRPV1, capsaicin triggers this process, which is why spicy foods taste hot.

Capsaicin doesn’t always act independently, though - certain substances can increase or decrease the hot feeling it creates. For instance, ethanol, a compound found in alcohol, magnifies the feeling by lowering “the temperature at which the capsaicin receptor activates,” according to BBC Future. As a result, capsaicin can more easily set off the perceived pain linked to TRPV1. On the other hand, milk is known to decrease the hotness of spice. The Sensory Evaluation Center in Penn State’s College of Agricultural Sciences conducted a study comparing the effects of different commercial drinks on subjects’ perceptions of spiciness after drinking a spicy Bloody Mary. It demonstrated that the protein content of milk is more important than the fat content of milk since there was almost no difference between the effectiveness of whole milk and skim milk. Specifically, a lipophilic, or fat-loving protein called casein found in mammal’s milk binds to capsaicin’s hydrocarbon tail. Approximately 80% of cow’s milk consists of casein, which is how it drastically reduces spiciness.

To measure the spiciness of chili peppers, a pharmacologist named Wilbur Scoville created the Scoville scale in 1912. The number represents the level of dilution for the spiciness to vanish, which means that a higher number would correlate with a spicier substance.

Pure capsaicin measures at about 16,000,000 average Scoville Heat Units, or SHUs. Chili peppers are much lower on the Scoville scale, though. A common pepper, such as jalapeño, falls around 5,000 SHUs. The spiciest pepper in the world is the Carolina Reaper, which sits at an average of 1,569,000 SHUs. However, the hottest Carolina Reaper to ever exist, named Smokin’ Ed’s Carolina Reaper, was tested to be 2.2 million SHUs.

Many humans crave the hot sensation and pain of spicy foods. Spice is a significant part of human culture globally, and thanks to TRPV1 receptors and substances to enhance or mitigate the feeling, humans get to experience it and control how they do so.



Hertzberg, Richie. “One Is the Human and the Other, Says a New Study, Is the Tree Shrew.”

National Geographic, 23 July 2018,


Du, Qian. “The Role of Transient Receptor Potential Vanilloid 1 in Common Diseases of the

Digestive Tract and the Cardiovascular and Respiratory System.” Frontiers, 21 Aug.


Greenwood, Veronique. “Food: How Spicy Flavours Trick Your Tongue.” BBC Future, 19 Jan.


Penn State. “Milk: Best Drink to Reduce Burn from Chili Peppers.” ScienceDaily, 25 June


Lewis, Jordan. “Why Does Drinking Milk Ease the Pain of Eating Spicy Food?” Psychology

Today, 16 Feb. 2017,


Team, The Alimentarium. “The Scoville Scale.” Alimentarium, 6 Jan. 2021,

Hallock, Betty. “World’s Hottest Pepper Hits 2.2 Million Scoville Heat Units.” Los Angeles

Times, 23 Jan. 2016,


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