Did you know that we have only one type of receptor for the sweet, sour, salty and savory tastes, but a whopping 25 types of taste receptors to detect the bitter taste?
What is up with bitter? Why so many bitter taste receptors? The answer will send you buying plenty of bitter greens on your next trip to the market.
Until recently, the standard American diet was overwhelming high in sweet and salty tastes, and very low in bitter tastes. Salt, as a preservative, was so valuable in ancient times that it was traded as a currency. We all got addicted to the sweet taste after our first taste of mother’s milk, which we have been craving ever since. Sweet, and to some extent salty, were tastes that were safe, edible and would not kill you.
Bitter tastes are not so straight-forward, some bitter plants are deadly. Poisons like strychnine and nicotine are quite bitter, activating bitter taste receptors to cough, spit and not swallow. Other bitter tastes seem to activate the immune system, protecting us from infection. (1,3)
Bitter tastes stimulate the cilia that line the respiratory tract to move faster in their effort to escort toxins to the throat, where they can be either swallowed, spit up, or coughed out. The problem is that not everyone is reactive to the bitter taste and the immune response to a bacterial invasion may be sluggish. (1,3)
People who are what scientists are calling “supertasters” have very reactive bitter taste receptors and get sick much less frequently than the non-bitter tasters. The ability for the bitter taste receptors to trigger an immune response is so powerful that many researchers believe that bitter-tasting medicines may someday replace antibiotics. (1,2)
Once the respiratory cilia are activated by an immune-boosting bitter taste, nasal cells will trigger the release of nitric oxide and thus kill the bacteria. These bitter tastes can trigger an immune response to a bacterial or viral agent in just seconds or minutes after exposure, while the more traditional immune response can take days or even weeks. (1,2)
Immunity Can Be Bittersweet
There are other bitter receptors that are paired with sweet receptors. When a bad bacteria comes into contact with one of these bitter receptors, they release a chemical called defensins, which kills the bacteria. The sweet receptors nearby sense the demise of the bacteria and then begin secreting glucose, a sweet taste that spreads the message, “the coast is clear, the sugar-eating bacteria are dead.” (1,2)
People who secrete too much glucose or sugar and are less responsive to the bitter tastes and get sick at higher rates, suggesting that we need to train our bitter receptors and un-train our sweet receptors. These taste receptors may prove to be more important than previously thought, as they are also found in the intestinal tract, lungs, pancreas and brain. (1,2) The research has only just begun.
Ayurveda’s Take On Taste
A balanced meal was not based on a measure of carbs, proteins and fats—rather, it was determined by a balance of all the five tastes. Each meal was required to have a bitter, pungent (spicy) sweet, sour, salty and astringent taste. Overeating any one of these (as we have with sweet and salty) can create a severe imbalance in mood, immunity and overall health.
While the research has not come to this conclusion yet, bringing our tastes back into balance may prove to be a therapy from the past for our future. I would suggest to actively work on breaking the taste addiction to sweet and salt, and intentionally add more bitter and astringent (cucumbers, beans, and pomegranates) to the diet.
The science is clear: excess sweet taste activation leads to a less robust immune response and those who have active bitter receptors have a much greater immune response.
Lee, Robert J et al. Bitter and sweet taste receptors regulate human upper respiratory innate immunity. J Clin Invest. 2014;124(3):1393–1405. doi:10.1172/JCI72094.
- Adappa, Nithin D et al. The bitter taste receptor T2R38 is an independent risk factor for chronic rhinosinusitis requiring sinus surgery. Int Forum Allergy Rhinol. 2014 January; 4(1): 3–7. Published online 2013 December 2.
Author: Dr. John Douillard
Editor: Renée Picard
Image: Merlene Goulet at Unsplash