There are tiny taste buds inside your mouth: On your tongue, in your throat, even on the roof of your mouth. What we call “flavor” is based on five basic tastes: sweet, salty, bitter, sour, and savory. These flavors — plus the sensations of heat, coolness, and texture, combine inside the mouth to give us a sense of taste. Along with how it tastes, how food smells is also part of what makes up its flavor.

When food tastes bland, many people try to improve the flavor by adding more salt or sugar. This may not be healthy for older people, especially if you have medical problems like high blood pressure or diabetes (high blood sugar).

People who have lost some of their sense of taste may not eat the foods they need to stay healthy. This can lead to other issues such as:

• Weight loss
• Malnutrition (not getting the calories, protein, carbohydrates, vitamins, and minerals you need from the food)

Eating food that is good for you is important to your health. If you have a problem with how food tastes, be sure to talk with your doctor.

Taste, also called gustation, and smell, also called olfaction, are the most interconnected senses in that both involve molecules of the stimulus entering the body and bonding to receptors. Smell lets an animal sense the presence of food or other animals—whether potential mates, predators, or prey—or other chemicals in the environment that can impact their survival. Similarly, the sense of taste allows animals to discriminate between types of foods. While the value of a sense of smell is obvious, what is the value of a sense of taste? Different tasting foods have different attributes, both helpful and harmful. For example, sweet-tasting substances tend to be highly caloric, which could be necessary for survival in lean times. Bitterness is associated with toxicity, and sourness is associated with spoiled food. Salty foods are valuable in maintaining homeostasis by helping the body retain water and by providing ions necessary for cells to function.

Tastes and Odors

Both taste and odor stimuli are molecules taken in from the environment. The primary tastes detected by humans are sweet, sour, bitter, salty and umami. The first four tastes need little explanation. The identification of umami as a fundamental taste occurred fairly recently—it was identified in 1908 by Japanese scientist Kikunae Ikeda while he worked with seaweed broth, but it was not widely accepted as a taste that could be physiologically distinguished until many years later. The taste of umami, also known as savoriness, is attributable to the taste of the amino acid L-glutamate. In fact, monosodium glutamate, or MSG, is often used in cooking to enhance the savory taste of certain foods. What is the adaptive value of being able to distinguish umami? Savory substances tend to be high in protein.

All odors that we perceive are molecules in the air we breathe. If a substance does not release molecules into the air from its surface, it has no smell. And if a human or other animal does not have a receptor that recognizes a specific molecule, then that molecule has no smell. Humans have about 350 olfactory receptor subtypes that work in various combinations to allow us to sense about 10,000 different odors. Compare that to mice, for example, which have about 1,300 olfactory receptor types, and therefore probably sense more odors. Both odors and tastes involve molecules that stimulate specific chemoreceptors. Although humans commonly distinguish taste as one sense and smell as another, they work together to create the perception of flavor. A person’s perception of flavor is reduced if he or she has congested nasal passages.

Reception and Transduction

Odorants (odor molecules) enter the nose and dissolve in the olfactory epithelium, the mucosa at the back of the nasal cavity (as illustrated below). The olfactory epithelium is a collection of specialized olfactory receptors in the back of the nasal cavity that spans an area about 5 cm² in humans. Recall that sensory cells are neurons. An olfactory receptor, which is a dendrite of a specialized neuron, responds when it binds certain molecules inhaled from the environment by sending impulses directly to the olfactory bulb of the brain. Humans have about 12 million olfactory receptors, distributed among hundreds of different receptor types that respond to different odors. Twelve million seems like a large number of receptors, but compare that to other animals: rabbits have about 100 million, most dogs have about 1 billion, and bloodhounds—dogs selectively bred for their sense of smell—have about 4 billion. The overall size of the olfactory epithelium also differs between species, with that of bloodhounds, for example, being many times larger than that of humans.

Olfactory neurons are bipolar neurons (neurons with two processes from the cell body). Each neuron has a single dendrite buried in the olfactory epithelium, and extending from this dendrite are 5 to 20 receptor-laden, hair-like cilia that trap odorant molecules. The sensory receptors on the cilia are proteins, and it is the variations in their amino acid chains that make the receptors sensitive to different odorants. Each olfactory sensory neuron has only one type of receptor on its cilia, and the receptors are specialized to detect specific odorants, so the bipolar neurons themselves are specialized. When an odorant binds with a receptor that recognizes it, the sensory neuron associated with the receptor is stimulated. Olfactory stimulation is the only sensory information that directly reaches the cerebral cortex, whereas other sensations are relayed through the thalamus.

Smell and Taste in the Brain

Olfactory neurons project from the olfactory epithelium to the olfactory bulb as thin, unmyelinated axons. The olfactory bulb is composed of neural clusters called glomeruli, and each glomerulus receives signals from one type of olfactory receptor, so each glomerulus is specific to one odorant. From glomeruli, olfactory signals travel directly to the olfactory cortex and then to the frontal cortex and the thalamus. Recall that this is a different path from most other sensory information, which is sent directly to the thalamus before ending up in the cortex. Olfactory signals also travel directly to the amygdala, thereafter reaching the hypothalamus, thalamus, and frontal cortex. The last structure that olfactory signals directly travel to is a cortical center in the temporal lobe structure important in spatial, autobiographical, declarative, and episodic memories. Olfaction is finally processed by areas of the brain that deal with memory, emotions, reproduction, and thought.

Taste neurons project from taste cells in the tongue, esophagus, and palate to the medulla, in the brainstem. From the medulla, taste signals travel to the thalamus and then to the primary gustatory cortex. Information from different regions of the tongue is segregated in the medulla, thalamus, and cortex.

Your ability to taste comes from tiny molecules released when you chew, drink, or digest food; these molecules stimulate special sensory cells in the mouth and throat. These taste cells, or gustatory cells, are clustered within the taste buds of the tongue and roof of the mouth, and along the lining of the throat. Many of the small bumps on the tip of your tongue contain taste buds. At birth, you have about 10,000 taste buds, but after age 50, you may start to lose them.

When the taste cells are stimulated, they send messages through three specialized taste nerves to the brain, where specific tastes are identified. Taste cells have receptors that respond to one of at least five basic taste qualities: sweet, sour, bitter, salty, and umami [oo-MOM-ee]. Umami, or savory, is the taste you get from glutamate, which is found in chicken broth, meat extracts, and some cheeses. A common misconception is that taste cells that respond to different tastes are found in separate regions of the tongue. In humans, the different types of taste cells are scattered throughout the tongue.

Taste quality is just one way that you experience a certain food. Another chemosensory mechanism, called the common chemical sense, involves thousands of nerve endings, especially on the moist surfaces of the eyes, nose, mouth, and throat. These nerve endings give rise to sensations such as the coolness of mint and the burning or irritation of chili peppers. Other specialized nerves create the sensations of heat, cold, and texture. When you eat, the sensations from the five taste qualities, together with the sensations from the common chemical sense and the sensations of heat, cold, and texture, combine with a food’s aroma to produce a perception of flavor. It is flavor that lets you know whether you are eating a pear or an apple.

Most people who think they have a taste disorder actually have a problem with smell. When you chew food, aromas are released that activate your sense of smell by way of a special channel that connects the roof of the throat to the nose. If this channel is blocked, such as when your nose is stuffed up by a cold or flu, odors can’t reach sensory cells in the nose that are stimulated by smells. As a result, you lose much of our enjoyment of flavor. Without smell, foods tend to taste bland and have little or no flavor.

Smell and taste are important senses. They can help you enjoy life—smell the flowers or savor your meal. They can also keep you safe. The smell of smoke can alert you to danger.

As you get older, your sense of taste or smell may fade. These senses are related. So when you can’t smell, you may also find that food tastes bland.

Often, loss of smell or taste isn’t cause for concern. It can be caused by many things. People with certain viruses can temporarily lose one or both senses.

When undergoing radiation and other cancer treatments, people may experience loss of smell and taste. This should return after the treatment stops.

Certain medications can also affect smell or make food taste different. An infection in the mouth, like gum disease, can leave a bad taste, too.

Sometimes the loss of smell or taste can be a sign of a more serious problem. Losing your sense of smell, for example, may be a symptom of Parkinson’s or Alzheimer’s disease. Tell your health care provider if you have any change in your sense of smell or taste.

If you’re having trouble smelling and tasting, adding colorful foods and spices to a dish can help. Try choosing brightly colored vegetables, like carrots or broccoli. Spices like mustard, garlic, and ginger can liven up a meal.

Many things can cause you to lose your sense of taste. If the salivary glands are damaged or aren’t producing enough saliva, this can affect taste. Most of the time there are ways to help with the problem.

A new loss of taste is a symptom that can occur with coronavirus infection. You should regain your sense of taste after all other symptoms have gone away, however if it doesn’t return, seek medical care as soon as possible.

Medications, like antibiotics and pills to lower cholesterol and blood pressure, can sometimes change how food tastes. Some medicines such as those for high blood pressure, depression, and bladder-control issues can make your mouth dry. Having a dry mouth can cause food to taste funny and also make it hard to swallow. Talk to your doctor if you think a medicine is affecting your sense of taste. There may be different medicines that you can try. Do not stop taking your medicine.

Gum disease, an infection in your mouth, or issues with your dentures can leave a bad taste in your mouth that changes the way food tastes. Brushing your teeth, flossing, and using mouthwash can help prevent these problems. Talk to your dentist if you have a bad taste in your mouth that won’t go away.

Alcohol can alter how food tastes. Cutting back or stopping drinking may help. Smoking can also reduce your sense of taste. Quitting may help.

If the foods you enjoy don’t smell or taste the way you think they should, talk to your doctor. He or she might suggest you see a specialist who treats people with smell and taste problems.This kind of doctor is called an otolaryngologist (oh-toh-lar-ing-gol-uh-jist), also known as an ENT (which stands for ear, nose, and throat). An otolaryngologist works on problems related to the ear, nose, and throat, as well as the larynx (voice box), mouth, and parts of the neck and face. The doctor may ask:

• Can you smell anything at all?
• Can you taste any food?
• When did you first notice the problem?
• Is the problem getting worse?
• Have you been told that you have allergies or chronic sinus problems?
• What medicines do you take?

There are likely ways to help fix the problem. If not, the doctor can help you cope with the changes in smell and taste.