Q. A year ago I had a car accident, and since then food doesn’t taste like it did before. Is this a serious problem?
A. The first thing you should do is consult an ear/nose/throat specialist to see whether your problem is a disorder of taste or smell. True taste disorders are rare compared to partial or total loss of the sense of smell, which will prompt around 200,000 people this year to consult their doctors.
Despite the close association in our minds, taste and smell are quite distinct senses. The tongue can recognize only four tastes (sweet, salty, sour, and bitter), perhaps five if you count umami, or savory, as some do). In contrast, humans can recognize as many as 10,000 different odors. Loss of the sense of smell – anosmia is the medical term – is also often due to injuries such as car accidents. For instance, about a third of football players have a reduced sense of smell from repeated blows to their heads.
The sense of smell is very important, though often taken for granted. Our sense of smell triggers the flow of saliva and the digestive juices that are necessary for the proper digestion and assimilation of food. Many people with anosmia skip meals because the appeal for food is not there, resulting in malnutrition and involuntary weight loss. Anosmia can also have the opposite effect, and a person may compensate for the loss of taste by overeating.
The nose is vitally important in detecting food flavors. It is common for people who lose their sense of smell to report that food “loses its taste.” What really happens is that food loses its aroma, and its taste, though still detectable, is rather monotonous. When we eat, the odors of the food go up the back of the throat into the nose. Because we put it in our mouth we think we “taste” the food, but it’s really the smell we detect. There is a specific site in the brain where we integrate taste and smell information, and the sum of taste and smell, or “flavor,” turns out to be about 75% smell.
The sense of smell is important not only to enjoy the taste of food, but it is essential for detecting danger signs such as smoke, gas leaks, and spoiled food. A person with anosmia needs to take extra safety precautions, such as installing extra smoke detectors and fire extinguishers, and switching to an electric range instead of a gas range since someone with anosmia cannot detect gas leaks. The sense of smell is also very important in detecting spoiled food, and leftovers need to be clearly marked with a “throwaway date.”
Though results have been inconsistent, zinc supplements are often recommended, along with vitamin A supplements, as treatment for anosmia. Recently liquid zinc gluconate nose drops have been recommended to treat the common cold. These should never be used, because direct application of zinc to the delicate membranes in the nose will actually cause anosmia.
Recently two American scientists were awarded the Nobel Prize for work done with what are called “G proteins,” influential proteins that translate signals from outside the cell (like smell) into cellular action. When G proteins do not work, they can lead to problems such as diabetes, alcoholism, infection, and even cancer. G proteins are presently the targets of intense medical research. We may find that loss of the sense of smell can do more than reduce your zest for life. It may even jeopardize your health.
This article appears in October 15 • 2004.