Bitter taste receptors

Ever wonder why some people don’t like Brussel sprouts or strong, dark coffee?  It turns out that there are common genetic variants that influence your perception of bitter compounds.

Taste Receptors

In genes where there is a lot of common variants, it is often the case that the variety of phenotypes, or traits, from the variants are an advantage to the population as a whole.

So why is it an advantage to have differences in our taste receptors?  Having part of the population able to taste a bitter toxin and warn of the danger is vital, while also having others who scarf down Brussels sprouts lets the community as a whole know that a bitter, but healthy, food is good to eat.

Taste buds on the tongue. By OpenStax – Wikimedia Commons.

Here’s an example:

One of the substances that some people can detect, at extremely low concentrations, is aristolochic acid, a toxin found in certain plant seeds.  In Eastern Europe, the plant tends to grow as a weed in fields, contaminating crops and causing kidney disease in those who ate the toxin. There is a 50-fold difference in people’s ability to taste aristolochic acid, although researchers are still trying to untangle the effects of taste ability vs the effect of the sensitivity of the gastrointestinal receptors on the disease-causing aspects of the toxin.  Needless to say, it would be an advantage to have someone in the village that can warn you that the crop is contaminated!

Receptors for more than just tasting:

We all know that we taste food in our mouth, but it turns out that these same receptors are also found in the gastrointestinal tract, in the airways, and in the urinary tract. New studies are coming out all the time on the various functions that these ‘taste’ receptors perform in the body.[study][study]


Genetic Variants for taste receptors

TheTAS2R gene family, containing 43 different genes, is responsible for various bitter taste receptors, while the TAS1R family (just two genes) is responsible for sweet and umami tastes.  Salty and sour taste receptors are still being sorted out, and it turns out we also have taste receptors for fat.

Bitter taste receptors:

TAS2R38 gene:
Linked to the taste of bitter in broccoli, Brussels sprouts, cabbage, watercress, chard, ethanol, and PROP. [ref][ref]   Non-tasters, or people who generally can’t detect the bitter taste, eat more vegetables, on the whole, when compared to tasters. [ref]

Interestingly, this taste receptor is also being studied as a target for type 2 diabetes medicines and is involved in triggering the production of bile acids.[ref][ref]

The TAS2R38 protein has recently been found to be expressed in adipose (fat) cells. Interestingly, people who are obese tend to have a lot more TAS2R38 in their fat cells compared to lean people. [ref]

Dietary intervention studies with a goal of increasing vegetable intake find that people who are able to taste the bitter compound in broccoli, etc are unlikely to increase their intake of vegetables, even when they are encouraged to do so.  On the other hand, people who can’t taste the bitter or are intermediate tasters did increase their vegetable consumption when encouraged to do so to prevent cardiovascular disease. [ref]

Check your genetic data for rs713598 (23andMe v.4 and v.5):

  • G/G: Can taste bitter in broccoli, etc.[ref]
  • C/G: Probably can taste bitter
  • C/C: Probably unable to taste some bitter flavors

Check your genetic data for rs10246939 (23andMe v4, v5):

  • C/C: Can taste bitter in broccoli, etc.
  • C/T: Probably can taste bitter
  • T/T: Probably unable to taste some bitter flavors, likely to consume more fruit and linked to obesity (Korean women)[ref]

TAS2R16 gene:
Associated with the taste of beta-glycorpyranoside [ref], which is in ethanol, bearberry, bacteria in spoilt or fermented foods, and willow bark (salicin).  [ref]  There have been studies looking into the link between TAS2R16 gene variants and colon cancer, pursuing the idea that either a variation in vegetable intake would affect cancer risk or a variation in the amount of natural salicin compounds eaten would affect colon cancer risk (aspirin being preventative in colon cancer for some). The studies done so far though haven’t been able to make that connection. [ref]

Check your genetic data for rs846672 (23andMe v.4 and v.5):

  • C/C: Can taste bitter in ethanol, fermented foods, etc
  • A/C: Probably can taste bitter
  • A/A: Probably unable to taste some bitter flavors

Check your genetic data for rs846664 (23andMe v.5 only):

  • A/A: Can taste bitter in ethanol, fermented foods, etc
  • A/C: Probably can taste bitter
  • C/C: less able to taste some bitter flavors

Check your genetic data for rs978739 (23andMe v.4 and v.5 only):

  • T/T: Can taste bitter in ethanol, fermented foods, etc
  • C/T: Probably can taste bitter
  • C/C: less able to taste some bitter flavors

TAS2R19 gene:
Linked to the taste of quinine,  the bitter taste of grapefruit and tonic water. [study]

Check your 23andMe results for rs10772420 (v.5 only):

  • A/A: Can taste bitter in quinine
  • A/G: Probably can taste bitter in quinine
  • G/G: Less able to taste bitter in quinine


TAS2R14 gene
:
Stevia taste receptor — as well as absinthe, aristolochic acid, fishberries, and Hoodia Gordonii.[study] [ref]  There is a polymorphism (rs2234001, covered by AncestryDNA but not 23andMe) that causes some people to detect stevia as bitter, some as only sweet, and some as sweet with a bitter aftertaste.  You don’t really need a genetic test for this one, though, since you can just taste some stevia and know whether you think it is sweet or bitter or both.

Of those who can taste bitter, some have a much strong perception of the bitter taste based on the rs3741843 variant. [study]

Check your 23andMe results for rs3741843 (v.4 only):

  • T/T: Lower sensitivity to bitter taste from stevia.
  • C/T: Stevia tastes more bitter (if able to taste the bitter)
  • C/C: Stevia tastes more bitter (if able to taste the bitter)

Sweet and Umami Taste Receptors:

TAS1R3 gene:
Sweet taste receptor for which variations are estimated to produce about a 16% difference in variability of sweet taste perception.  This receptor also plays a role in umami taste as well, along with another gene. [ref] A study found an increase in kid’s cavities linked to those who have a decreased sensitivity to the taste of sugar, perhaps due to eating more sugar to reach the same perception as those without the variant.  Scientists are still sorting out the reason why and how the change in the taste receptor protein is also altering insulin secretion.  [study]

Check your 23andMe results for rs35744813 (v.4 only):

  • T/T: Decreased taste sensitivity for sucrose
  • C/T: Somewhat decreased taste sensitivity for sucrose
  • C/C: Normal taste receptor for sucrose

Check your 23andMe results for rs307355 (v.5 only):

  • T/T: Decreased taste sensitivity for sucrose
  • C/T: Somewhat decreased taste
  • C/C: Normal taste sensitivity for sucrose

 

More to read:
Here are a few more studies that are digging into the roles that our taste receptors play –outside of just the taste we perceive in our mouth.  Read through them to find out the more about the interactions of leptin, endocannabinoids, and insulin with taste receptors.  Pretty cool stuff!



Author Information:   Debbie Moon
Debbie Moon is the founder of Genetic Lifehacks. She holds a Master of Science in Biological Sciences from Clemson University. Debbie is a science communicator who is passionate about explaining evidence-based health information. Her goal with Genetic Lifehacks is to bridge the gap between scientific research and the lay person's ability to utilize that information. To contact Debbie, visit the contact page.