A non-taster is someone who cannot detect the bitterness of certain chemical compounds, most notably phenylthiocarbamide (PTC) and a related substance called PROP. Roughly 25 to 30 percent of people with European ancestry are non-tasters, though the rate varies widely across populations. The trait is genetic, tied to a specific receptor on the tongue, and it influences more than just reactions to lab chemicals. It shapes how you experience bitter foods like broccoli, kale, and coffee.
The Gene Behind Taste Blindness
Whether you’re a non-taster comes down almost entirely to one gene: TAS2R38. This gene builds a bitter taste receptor on the surface of your tongue’s taste cells. It contains three key points where the DNA code can vary, and the combination of those variants determines how well (or poorly) the receptor detects certain bitter molecules.
The two most common versions of the gene are known by shorthand as PAV and AVI. PAV is the “taster” version, and it’s dominant, meaning you only need one copy to taste bitterness. AVI is the “non-taster” version and is recessive. If you inherit AVI from both parents, your bitter receptors essentially don’t respond to PTC or PROP, and you’re classified as a non-taster. People who carry one PAV and one AVI copy can taste the bitterness, though sometimes less intensely than someone with two PAV copies. In large genetic surveys, the AVI version actually turns up slightly more often than PAV, at about 53 percent of all copies of the gene compared to 42 percent for PAV.
How Non-Taster Status Is Tested
The classic test is simple: place a small amount of PTC or PROP on a person’s tongue and ask if it tastes bitter. PROP is preferred in modern research because PTC has a sulfurous smell and some toxicity concerns. The test substance is typically delivered on a paper strip or in solution at increasing concentrations.
Most tasters detect bitterness at very low concentrations, often below 100 nanomoles of PROP. Non-tasters, by contrast, can’t identify bitterness even at concentrations of 800 nanomoles or higher. In one validation study, a participant with two copies of the AVI gene couldn’t detect bitterness at 1,000 nanomoles per taste strip. Researchers use this sharp divide in sensitivity to draw a line between tasters and non-tasters. In that study, 26 percent of participants fell into the non-taster category.
Non-Tasters, Tasters, and Supertasters
People typically fall into three broad groups. Non-tasters perceive little or no bitterness from PTC and PROP. Tasters detect it clearly. And supertasters, who usually carry two copies of the PAV gene and tend to have a higher density of taste structures on their tongue, find these compounds intensely bitter. For supertasters, foods like raw broccoli, grapefruit, and black coffee can be almost unbearably sharp. Non-tasters, on the other hand, often have no issue with these foods and may even enjoy them.
Some rare gene combinations, like AAI or AAV, produce intermediate sensitivity. These individuals fall somewhere between full tasters and non-tasters, detecting some bitterness but at higher thresholds than typical tasters.
How Common Non-Tasters Are
The percentage of non-tasters varies dramatically by population. Among people of European descent (including non-Hispanic white Americans), about 27 to 28 percent are PTC non-tasters. Australian Aboriginal populations have rates around 50 percent. Most African, Asian, and Native American populations have lower rates, averaging between 10 and 16 percent. These figures come from a review of more than 370 population samples collected worldwide between 1934 and 1998.
This global variation is itself a clue that evolutionary pressures have shaped the trait differently in different environments.
Why Non-Tasters Still Exist
If bitter taste perception helps animals avoid toxins, you might expect natural selection to have eliminated the non-taster gene long ago. Instead, both versions of TAS2R38 have persisted in human populations for hundreds of thousands of years. Geneticists call this balancing selection, and it was first proposed by the statistician R. A. Fisher in 1939.
The leading explanation is that each version of the gene offers a different advantage. PTC itself doesn’t occur in nature, but it’s structurally similar to bitter compounds called isothiocyanates and goitrin, which are found in cruciferous vegetables like cabbage and broccoli. Tasters may be better at detecting and avoiding these compounds when they signal toxicity. But there’s a cost: tasters may also avoid nutrient-rich vegetables that happen to taste bitter, potentially missing out on beneficial nutrients.
One intriguing hypothesis is that the non-taster version of the receptor isn’t actually broken. It may bind to a different set of bitter molecules that researchers haven’t yet identified, giving non-tasters their own distinct protective repertoire. If true, people who carry one copy of each version (heterozygotes) could detect the widest range of bitter toxins, which would explain why both versions have been preserved.
Effects on Diet and Body Weight
Because non-tasters don’t experience the same aversion to bitter flavors, they tend to accept a wider range of foods, including vegetables and other bitter-tasting items that tasters and supertasters may avoid. This sounds like it should be a health advantage, and in some ways it is. Non-tasters are generally less picky eaters.
However, the same reduced sensitivity extends to fats and sugars. Non-tasters often show less sensitivity to the richness of high-fat foods, which can lead to higher calorie intake without the same feeling of “that’s enough.” Research in children ages three to six found that non-tasters were heavily concentrated in the overweight category, with 73 percent of non-tasters classified as overweight compared to tasters, who skewed toward the underweight category. The relationship between taste perception and body weight appears to start early in life.
Non-tasters also have a slightly higher susceptibility to thyroid-related conditions. Because they don’t taste the goitrin in cruciferous vegetables as readily, they may consume more of these compounds without the aversion response that would limit intake in tasters. In certain dietary contexts, this can interfere with thyroid function.
What Non-Tasters Experience Day to Day
Being a non-taster isn’t something most people notice unless they’re tested. You won’t experience a blank sensation where flavor should be. Your other taste receptors for sweet, salty, sour, and savory work normally. What changes is the intensity of bitterness in specific foods. Black coffee tastes smoother. Dark chocolate is less sharp. Hoppy beer is more approachable. Raw kale or arugula won’t have the same bite.
If you’ve ever wondered why some people can’t understand complaints about bitter vegetables while others find them genuinely unpleasant, the answer is often sitting in the TAS2R38 gene. The difference is real, measurable, and entirely outside your control.