Work. Family. Bills. The Future. These are a few of the life factors that are stressful to the average person. When many biologists study stress, especially from a hormonal perspective, we focus on how these various sources of stress are transformed into hormonal signals in the body. Research has demonstrated that our abilities to detect low (read: weak) concentrations of both smell and taste stimuli are significantly impeded by stress. The longer or more severe the stress, the more impaired our abilities to smell and taste. For instance, when you eat something pleasing, say, a piece of wedding cake, your body releases tons of signals that travel through your blood stream and nervous system to activate other processes.
What Happens When You Have Your Cake and Eat it too
When you eat that piece of cake, the first experiences are the taste, smell and flavor of the food. You taste the sweetness of the sugar and the richness of the butter in the icing. These experiences result from the actions of taste cells in your taste buds. They sense the sugar and the fats and release hormones and other chemicals that tell your brain that you have sugar and fat in your mouth. If you were to close your nose before eating that piece of cake, that would be almost all you would experience.
If you were to eat the wedding cake with an open nose, you would notice all of the aromas, perhaps vanilla or almond extract, lemon essence, or rose water. In fact, most people would describe the “taste” of wedding cake to be sweet with hints of these odors when, in fact, those are the scents that combine with our taste qualities to create the flavor experience. Flavor is the simultaneous unification of taste and smell information in our brains. The flavor of wedding cake is a unique identifier, just as the flavor of a dreamsicle—sweet cream and sour citrus with vanilla and orange aromas—is its own identifiable experience.
Stress Makes You Want More Sugar and Fat
Studies show that stress can affect both taste and smell. If increased amounts of stress reduce our ability to detect, say, sweet compounds, it follows that a higher concentration of sweets would be required for us to find them pleasing. For example, think about the amount of sugar you add to your coffee or tea. If stress inhibits your ability to detect a teaspoon of sugar in your coffee, which you normally find sufficiently sweet, you may end up adding a second teaspoon of sugar just to maintain, not enhance, your food experience. You have effectively doubled the amount of sugar in your cup of coffee simply to “enjoy it” the same as you always do.
Sugar is not just for your coffee, though. It’s in virtually every food we consume on a daily basis. We have known for quite some time that obesity and stress are linked, but from the taste perspective, researchers have recently shown that obese people (and rodent models) become desensitized to numerous tastes, especially fats and sugar. The natural inclination of people who become desensitized is to reach for something sweeter when the normal amount of sugar isn’t cutting it. That sets the stage for excessive calorie consumption and obesity.
Differences in Taste Caused by Stress
Our recent paper demonstrated that taste buds themselves are targets of stress hormones. When you experience a stressful event that is either short, like a sudden shock, or prolonged, like taking care of a newborn baby for months, your body’s stress responsiveness is altered. In the case of acute stress, your adrenal glands are signaled to immediately release glucocorticoids (GCs). GCs flood into the blood stream and then travel throughout the body where they have significant effects on cells and tissues that express the GC receptor: GR.
We found that GR is present in taste bud cells. However, it wasn’t in all cells of the taste bud—it was selectively expressed in the type of taste cells that respond to sweet, umami (savory), and bitter taste stimuli.
A taste bud is an interesting biological structure. It is shaped a little bit like an artichoke, where each petal would be an individual taste cell. What’s neat about taste buds is that not every cell responds to the same taste stimuli. For instance, you might have one cell that responds to only sweet (e.g., sugar, Splenda) and umami (e.g., MSG) compounds, and another cell might only respond to sour compounds (e.g., citrus acid, vinegar). So an entire taste bud could respond to every taste compound type (sweet, sour, umami, bitter, salt, mineral, fat) but it delegates the responsibility of individual tastes to different types of cells within the bud.
Since we discovered GR expression in sweet/umami/bitter cells, we wanted to see what happens to these receptors in the taste buds during stress. Therefore, we collected acutely stressed mice, since rodents are great research models for understanding mammalian biology. When observing the taste buds of stressed mice versus unstressed controls, we noticed that the stressed mice exhibited GR activity, specifically the movement of GR into taste cell nuclei. GR only mobilizes to the nuclei of cells when it is activated by stress hormones, which we concluded was occurring in these stressed mice. This may mean that stress could eventually lead to changes in taste sensitivity by switching off certain taste genes.
Taste Buds Share Feelings of Stress with You
Our findings revealed that your taste buds “feel” the effects of stress just like other parts of your body—they are not protected from stress. This matters because our taste buds, along with our noses, are the first point of contact between us and food. What happens during that first interaction can determine how much of something we will eat and if we will prefer that food over something different. Think of your taste buds as the guardians of your digestive system. If they are functioning properly, your body can maintain a healthier condition. However, if because of excessive stress in your life your chemical senses become less sensitive, your ability to properly assess the foods you consume could become compromised.
What we have observed in taste buds is not unique among the body’s sensory systems. Indeed, GR is expressed and active in hearing cells of your ear, retinal cells of your eye and even olfactory cells in your nose. Moreover, GR in these other sensory tissues can be activated by stress as well. This could ultimately mean that long term stress may handicap us wholesale. Therefore, the proper management of our personal stress, especially stress or anxiety which is prolonged, is undoubtedly crucial to our personal health.
1.M. Rockwell Parker, Dianna Feng, Brianna Chamuris, Robert F. Margolskee. Expression and nuclear translocation of glucocorticoid receptors in type 2 taste receptor cells. Neuroscience Letters, 2014; 571: 72 DOI:10.1016/j.neulet.2014.04.047
Rocky Parker, a Visiting Assistant Professor at Washington and Lee University, has a background in steroid hormone physiology. His research spans from discovering sex pheromone regulation in snakes during his Ph.D. at Oregon State University to examining the endocrine-sensory system interaction in mice during his postdoctoral studies at Monell. Besides conducting physiological research, he is dedicated to teaching, mentoring young scientists, and communicating science effectively to diverse audiences.