A Question of Taste -- Or Is It Smell?
Sometimes when we talk about taste, we're really talking about smell. Much of our experience of the "taste" of food is what we smell of the food in our mouths, experts say.
Our taste buds are important, but smell seems to play a bigger role. Most people who complain of loss of the sense of taste are surprised to learn they are actually having problems with their sense of smell. A more accurate word for the sense of taste, experts say, might be the sense of flavor.
Airborne molecules that reach the nose stimulate olfactory cells. Food in the mouth or throat stimulates gustatory (taste) nerve cells. Both types of nerve cells send messages to the brain. The brain assesses the information on smell and taste to identify the source. These nerve cells are the only ones the body replaces when they become old or damaged. If part of the tongue, or the cranial nerve connected to a part of the tongue, is damaged, for example, the other portions of the tongue will take over the function of that damaged portion.
Flavors such as salty, bitter, sweet and sour can be recognized by the brain without involving the sense of smell. It is the complex flavors that need input from both senses to be experienced.
Other nerve cells in the moist areas of the mouth, nose, throat and eyes identify other sensations, such as the cool feeling from peppermint or the bite of a chili pepper, that contribute to the experience of taste and smell.
The sense of taste remains stable over your lifetime. Although aging may seem to affect the taste of food, it's actually the sense of smell that begins to decline around age 60. Other causes for a poor sense of smell or taste include a head injury; upper respiratory infections, which can cause temporary or permanent loss; polyps in the nose or sinuses; hormone problems; dental problems; dry mouth; radiation therapy to head or neck; tobacco smoking; prolonged exposure to chemicals; and certain medications.
No 'tongue map'
A popular myth about taste is that we experience sweetness at the tip of the tongue, salt at the sides of the tongue, and bitterness at the back. But experts say that there's no such thing as a "tongue map." Taste buds are located in an oval around the tongue, with few in the center. You can experience any of the four main tastes -- sweet, sour, salty and bitter -- in any of those areas.
When it comes to taste, we're not created equal. Genetically speaking, there's a breed of "super-tasters" who have many, many more taste buds than most, making them more sensitive to sweet and bitter. Research indicates that about a fourth of us are super-tasters, and most are women.
Are you a super-taster? Look in the mirror, and stick out your tongue. Look for red, round structures. (A few drops of milk will make them stand out.) Compare your taste bud total with that of your friends. If you've got more, you may be a super-taster.
Bitter is tops
Our ability to taste bitterness is the most highly developed taste. We can detect the presence of a bitter taste in as little as 1 part per 200,000. In comparison, we detect sweets in about 1 part per 200. Experts say this may be a built-in safety mechanism for detecting poisonous plants when looking for food: We can detect the bitter poisonous alkaloids in plants without having to eat enough to get sick from them.
Although much of our taste sensation comes from the sense of smell, foods like hot peppers are the exception. They are actually experienced on the tongue chemically, and are described more correctly as pain sensation because the taste buds are wrapped in pain fibers.