Taste Receptors: Bitter, sweet, and much more

Ever wonder why some people don’t like dark chocolate or broccoli? Others love dark roast coffee and think that Brussel sprouts taste just great.

It turns out that we are all different in our ability to taste bitter in things — like stevia or even certain flavors in alcohol. Some people are wired not to notice sweet flavors as much as others.

This article, though, isn’t only about how we perceive foods. These taste receptors also act as chemical receptors throughout the body, impacting our health from our nose through our gut.  Members will see their genotype report below, plus additional solutions in the Lifehacks section. Consider joining today 

Taste Receptors

If you are old enough, you may remember the Life cereal commercials with Mikey, where the ultimate, picky taste test is whether “Mikey likes it!

It turns out that we all taste things differently. Multiple taste receptors add to our perception of taste. Plus, genetic variants combine together to make our sense of taste unique. Your idea of what dark chocolate tastes like is different than mine!

One thing that genetics research shows us is that having a lot of variation is good for some tasks in the body.

So why is it an advantage to have differences in our taste receptors? 

Think about your ancestors living in a village, gathering foods for dinner. Having part of the community able to taste a bitter toxin and warn of the danger is vital. But, it is also important to have others scarf down Brussels sprouts to let the community as a whole know that a bitter but healthy food is good to eat.

Let me give you 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 agricultural fields, contaminating crops and causing kidney disease. There is a 50-fold difference in people’s ability to taste aristolochic acid. Additionally, that ‘taste’ receptor is located in the intestines.  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.

A lot of our biology is centered around food. Our brain controls our appetite, driving us to go out and obtain food (either through going to get take-out or physically hunting and gathering :-) Our body is formed to put us at the top of the food chain, able to hunt down animals and work the fields in agriculture.

Key to survival, our taste buds are essential for knowing whether the food contains the nutrients our body needs – and whether it is safe to eat. We instinctively know that a ripe strawberry is delicious, but a slightly over-ripe strawberry that starts to decay a bit (bacteria, mold) is disgusting.

How do taste receptors work?

We all learned early in our education that we have taste buds on our tongues to tell us about sweet, bitter, sour, salty, and umami (savory)flavors.

The cells that make up our taste buds abundantly produce taste receptors on the surface of the cells. These receptors bind to specific molecules from foods and send a signal to the brain – signaling for sweet or bitter as well as indicating the intensity of the flavor.[ref]

The sweet and umami tastes are encoded in three genes in humans – and most animals. It turns out that many animals are attracted to sweet tastes, indicating an easy source of energy.[ref]

There are a number of different genes that encode bitter taste receptors — and there are quite a few different molecules that we humans detect as being bitter.

Salty tastes are detected by receptors known as epithelial sodium channels. These are receptors that are sensitive to ions and can detect different concentrations. Salty tastes aren’t just limited to table salt (sodium chloride); other molecules like lithium chloride and potassium chloride also taste salty.[ref]

The image below represents the different receptors available on taste buds for sweet, umami, bitter, and salty.[ref]

Taste receptors on a taste bud. Creative Commons Image license.

 

Taste receptor variants and food choices:

Unsurprisingly, people tend to eat more of the foods they like and less of the food they don’t like. (Yes, lots of research money spent to figure out what every parent knows!)

The heritability, or genetic component of food preference, is around 50% for most types of foods. The other half of the equation is all the other variables – cultural habits, which foods were introduced to kids, when foods were introduced, psychological factors, etc.[ref]

Hormones change your perception and desire for certain foods:

  • The endocannabinoids (and cannabinoids) increase your sensitivity to sweets, while leptin (full signal) decreases your taste for sweets.
  • Ghrelin, the hunger hormone, increases your taste for salty and sour foods.[ref]

Related articles: Ghrelin Genes and Endocannabinoid genes and weight loss

Taste receptors aren’t limited to the mouth:

The taste receptors are just that – a cellular receptor for a specific type of molecule.

  • When in the mouth, the receptor causes a signal to the brain of ‘bitter’ or ‘sweet’.
  • That same receptor triggers other responses when located in other cell types.

Basically, the taste receptors work kind of like a lock and key. A specific chemical comes along that can bind only to a specific receptor on the surface of a cell. That binding or activation then triggers an action to happen within the cell.

Taste receptors are expressed on chemoreceptive epithelial cells throughout the respiratory and intestinal tract. These receptors don’t trigger a ‘taste’ sensation to be sent to the brain. Instead, they trigger a variety of other reactions to happen.

For example, in the sinuses, one of the bitter taste receptors is triggered by certain bacterial byproducts, causing nitric oxide production and nose cilia movement. It helps to kill that specific bacteria and move it out.

Related article: Genetics and chronic sinus infections

In other cells in your nose, sweet taste receptors also are activated by certain bacterial products. These sweet receptors decrease the immune response and are linked to effects from commensal bacteria.[ref]

Taste receptors are also found in cells throughout the body, including the pancreas, bladder, thyroid, liver, brain, and testes. Yep, taste receptors in sperm… I’ll come back to this.[ref]

What are all of the receptors doing? Well, let’s take the sweet taste receptors in the bladder as an example. It turns out that artificial sweeteners, such as saccharine, make some people feel like peeing more is due to sweet taste receptors in the bladder causing it to contract.[ref]

There are bitter taste receptors that are important in the thyroid gland, and bitter taste receptor variants influence the risk of thyroid cancer.[ref]

Similarly, researchers have found that certain bitter taste receptors are downregulated in breast cancer tissue. These are the same receptors associated with bitter compounds, such as bitter melon extract and chloroquine, which inhibit tumor growth in breast cancer cells.[ref]

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 on the various functions that these ‘taste’ receptors perform in the body.[ref][ref]

I can’t leave you dangling without explaining taste receptors in the testes… It turns out that there are taste receptors for umami tastes in the sperm, and they affect male fertility (in animal studies). There are also bitter taste receptors in the testes and in sperm. A recent study showed that about 80% of sperm have measurable bitter taste receptors – and that there is a great variety of which ones are expressed in the sperm. Other research indicated that taste receptors might be important in sperm cilia motility.[ref][ref]

 


Taste Receptors Genotype Report

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The TAS2R 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 receptor genes:

TAS2R38 gene: codes for the receptor linked to the taste of bitterness in broccoli, Brussels sprouts, cabbage, watercress, chard, ethanol, and PROP.[ref][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.

Check your genetic data for rs713598 (23andMe v4, v5; AncestryDNA):

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

Members: Your genotype for rs713598 is .

Check your genetic data for rs10246939 (23andMe v4 and v5; AncestryDNA)

  • C/C: Can taste bitter in broccoli, etc.
  • C/T: Probably can taste bitter
  • T/T: Probably unable to taste some bitter flavors

Members: Your genotype for rs10246939 is .

 

TAS2R16 gene: codes for the receptor associated with the taste of beta-glycorpyranoside[clinvar], which is in ethanol, bearberry, bacteria in spoilt or fermented foods, and willow bark (salicin).[ref]

Studies on these variants look at the link between TAS2R16 gene variants and colon cancer, pursuing the idea that a variation in vegetable intake would affect cancer risk. Another theory is that the variation in the number of natural salicin compounds eaten would affect colon cancer risk (aspirin being preventative in colon cancer for some). The studies done so far haven’t been able to make that connection.[ref]

Check your genetic data for rs846672 (23andMe v4):

  • 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

Members: Your genotype for rs846672 is .

Check your genetic data for rs846664 (23andMe v5; AncestryDNA):

  • 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

Members: Your genotype for rs846664 is .

Check your genetic data for rs978739 (23andMe v4 and v5):

  • 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

Members: Your genotype for rs978739 is .

 

TAS2R19 gene: is linked to the taste of quinine, the bitter taste of grapefruit, and tonic water.[ref]

Check your genetic data for rs10772420 (23andMe v5; AncestryDNA):

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

Members: Your genotype for rs10772420 is .

TAS2R4 gene: bitter taste receptor that responds to stevia, chloroquine, PTC, and denatonium benzoate.

Check your genetic data for rs2234001 (AncestryDNA):

  • GG: a bitter taste for stevia
  • C/G: a mix of bitter vs. sweet tasters
  • C/C: a sweet taste for stevia[ref], part of a haplotype associated with reduced thyroid cancer risk.[ref]

Members: Your genotype for rs2234001 is .


TAS2R14 gene: bitter taste receptor — stevia, absinthe, aristolochic acid, fishberries, and Hoodia Gordonii.[ref][ref]

Of those who can taste bitter in stevia (from TAS2R4 above), some strongly perceive the bitter taste based on the TAS2R14 rs3741843 variant.[ref]

Check your genetic data for rs3741843 (23andMe v4; AncestryDNA):

  • T/T: Lower sensitivity to bitter taste from stevia; better sperm motility
  • C/T: Stevia tastes more bitter (if able to taste bitter); better sperm motility
  • C/C: Stevia tastes more bitter (if able to taste bitter)[ref]; decrease sperm motility[ref]

Members: Your genotype for rs3741843 is .

Sweet and Umami Taste Receptor Genes:

TAS1R3 gene: codes for a 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] Umami, or savory flavors, are due to the detection of l-glutamate in foods.

One study found an increase in kids’ 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 why and how the change in the taste receptor protein is also altering insulin secretion.[ref]

Check your genetic data for rs35744813 (23andMe v4 ):

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

Members: Your genotype for rs35744813 is .

Check your genetic data for rs307355 (23andMe v5 only):

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

Members: Your genotype for rs307355 is .

Salty taste receptor genes:

SCNN1A gene: codes for a salt-sensitive receptor. These receptors are found in our salt taste receptors as well as elsewhere in the body. Genetically, some are linked with being more or less likely to have blood pressure sensitive to the amount of salt in the diet.

Check your genetic data for rs11614164 (AncestryDNA):

  • A/A: typical
  • A/G: blood pressure less likely to be salt-sensitive
  • G/G:  blood pressure less likely to be salt-sensitive[ref]

Members: Your genotype for rs11614164 is .

 


Lifehacks:

Your gut knows the difference between sugar and artificial sweeteners. While both may taste sweet and signal ‘sweet’ to the brain, receptors in the gut respond via that vagus nerve to real sugar – and don’t respond to artificial sweeteners. Basically, the gut gives positive feedback to the brain when sugar is ingested.[ref]

Zinc is integral to our ability to taste. When it comes to the ability to taste salt, a zinc deficiency can cause you to eat more salt.[ref]

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About the Author:
Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering and also an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.