Problems with Taste
About Problems with Taste
Taste, or gustation, is one of our most robust senses. Unlike the sense of smell, normal aging does not greatly affect our sense of taste.
Taste helps us recognize when food is good or bad for us. But, even more important, loss of taste can cause a loss of appetite, especially in older adults, which can lead to loss of weight, poor nutrition, weakened immunity, and even death.
How Our Sense of Taste Works
Our sense of taste, along with our sense of smell, is part of our chemical sensing system. Normal taste occurs when tiny molecules released by chewing or the digestion of food stimulate special sensory cells in the mouth and throat. These taste cells, or gustatory cells, send messages through three specialized taste nerves to the brain, where specific tastes are identified. Damage to these nerves following head injury can lead to taste loss.
The taste 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 that can be seen on the tip of the tongue contain taste buds. At birth, we have about 10,000 taste buds scattered on the back, sides, and tip of the tongue. After age 50, we may start to lose taste buds.
Five Taste Sensations
We can experience five basic taste sensations: sweet, sour, bitter, salty, and umami, or savory. Umami was discovered by a Japanese scientist in the early part of the twentieth century. It is the taste of glutamate, a building block of protein found in chicken broth, meat stock, and some cheeses. Umami is the taste associated with MSG (monosodium glutamate) that is often added to foods as a flavor enhancer.
The five taste qualities combine with other oral sensations, such as texture, spiciness, temperature, and aroma to produce what is commonly referred to as flavor. It is flavor that lets us know whether we are eating an apple or a pear.
Flavors and the Sense of Smell
Many people are surprised to learn that we recognize flavors largely through our sense of smell. Try holding your nose while eating chocolate. You will be able to distinguish between its sweetness and bitterness, but you can't identify the chocolate flavor. That's because the distinguishing characteristic of chocolate is largely identified by our sense of smell as aromas are released during chewing. Food flavor is affected by a head cold or nasal congestion because the aroma of food does not reach the sensory cells that detect odors. More information on this topic can be found in the chapter "Problems with Smell."
Smell and Taste Closely Linked
Smell and taste are closely linked senses. Many people mistakenly believe they have a problem with taste, when they are really experiencing a problem with smell. It is common for people who lose their sense of smell to say that food has lost its taste. This is incorrect; the food has lost its aroma, but taste remains. In older people, there is a normal decline in the sense of smell and the taste of food shifts toward blandness. This is why people often believe they have a taste problem.
Some people are able to taste a bitter compound known as phenylthiocarbamide, or PTC, while other people are not. According to some taste researchers, about 25 percent of Americans are nontasters of the chemical compound, 50 percent are medium tasters, and 25 percent are supertasters. This information is important because one's sensitivity to bitter-tasting substances affects the choices a person makes about which foods to eat. Supertasters tend to find many tastes more intense than other people do, and avoid strong-tasting foods, especially bitter-tasting vegetables (such as broccoli and Brussls sprouts, coffee, and alcohol.
In addition, some people are more sensitive to the taste of sweet than other people, which could influence how much sugar they eat. NIDCD researchers have found that very small differences in DNA near the gene that encodes a portion of the sweet taste receptor play a big role in determing whether a person is sensitive to the taste of sugar. What's more, the researchers discovered that certain variations occur more often in different groups of people. People of European ancestry are more likely to be sensitive to the taste of sweet, people of Asian ancestry have medium sensitivity, and people of sub-Saharan African ancestry are more likely to have a reduced sensitivity.
When Taste is Impaired
A distorted sense of taste can be a serious risk factor for heart disease, diabetes, stroke, and other illnesses that require sticking to a specific diet. When taste is impaired, a person may change his or her eating habits. Some people may eat too little and lose weight, while others may eat too much and gain weight.
Loss of taste can cause us to eat too much sugar or salt to make our food taste better. This can be a problem for people with certain medical conditions, such as diabetes or high blood pressure. In severe cases, loss of taste can lead to depression.
Taste Problems in Older Adults
When an older person has a problem with taste, it is often temporary and minor. True taste disorders are uncommon. When a problem with taste exists, it is usually caused by medications, disease, some cancer treatments, or injury.
Many older people believe that there is nothing they can do about their weakened sense of taste. Depending on the cause of your problem, your doctor may be able to suggest ways to regain your sense of taste or to cope with the loss of taste. In many cases, the loss of taste turns out to be a loss of smell. If you think you have a problem with your sense of taste, see your doctor.