Ask the Doctors

Dear Doctor: Does loss of taste occur naturally with old age, or could it be a symptom of an illness? I'm 89, in pretty good shape with good blood pressure, but seem to be losing my sense of taste.

Dear Reader: While it's true than an impaired sense of taste can be related to illnesses that range from a simple cold to a complex neurological disorder, by the time one is 89 (congratulations, by the way!) it's more likely that the decline is age-related. To understand why, we need to talk about two of our senses -- taste and smell.

Let's begin with a tiny and amazing organ -- the taste bud. We enter the world with about 10,000 taste buds, each of which is made up of between 10 and 50 sensory cells. These cells are bundled together like the sections of an orange, and are connected to a complex web of nerve fibers.

Each bundle is tipped with a fluid-filled pore that behaves as a funnel and, via minute fibers known as taste hairs, delivers molecules to the sensory cells to be "tasted." The nerve fibers send chemical messages from the taste buds to the brain, where they are interpreted as sweet, salty, bitter, sour and savory, also referred to as "umami."

The taste buds themselves are tucked into undulating walls and grooves on the surface of the tongue, which are known as papillae. The papillae greatly increase the surface area of the tongue. This allows for a significant increase in sensitivity without a corresponding increase in the size of the tongue. Additional tasting cells are found on the roof of the mouth and along the lining of the throat.

As you may have noticed, we recover from a bite or burn to the tongue far more quickly than to other parts of the body. This is due to the remarkable rate at which the sensory cells in the taste buds can regenerate. As we age, though, these cells tend to regenerate more slowly. This affects our sense of taste.

At the same time, our sense of smell, which plays a crucial role in our ability to taste and distinguish the subtleties of flavors, also begins to diminish. When we chew, volatile molecules travel via the nasal cavity from the mouth to the nose. There, as on the tongue, highly specialized cells send signals to the brain, where the incoming data get interpreted as flavor.

Research shows that what is perceived as a loss in the sense of taste is, in fact, often a loss in the sense of smell. The tongue will tell us that something is sweet. But it's the sense of smell allows us to say whether that sweet bite is a peach or an apricot.

A diminished sense of smell has many causes. If the decline in your ability to taste is sudden or severe, a visit to your primary care physician is a good idea. He or she can perform tests to assess the degree of the loss, conduct a physical exam to rule out chronic conditions or disease, and propose medical treatment, if appropriate.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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