What Happens to Your Taste Without Smell?

The tongue detects only five tastes: sweet, sour, salty, bitter and umami, a savory taste researchers first isolated in the form of monosodium glutamate. All of the other characteristics that people call taste are more properly assigned to the olfactory sense. Chewing food releases scents via the back of the nasal passages where olfactory neurons perceive them as complex flavors. Without the sense of smell--a condition doctors term anosmia--the sense of taste becomes severely limited.

Lessening of Taste

• With temporary conditions such as a case of sinusitis or a common cold, nasal congestion causes partial anosmia that diminishes the flavor of foods and beverages. The patch of olfactory neurons at the base of the nasal passages remains active, but less air can pass over these sensory nerves. With less of an air current, fewer scent molecules make their way to the neurons, leaving food with less perceptible flavor aside from the five basic tastes.

Inability to Taste

• Total anosmia--the complete inability to smell--can result from neurological damage in the brain or to the olfactory neurons. Disease, injury and malnutrition can cause this disorder. People who suffer from total anosmia taste only the fundamental flavors. They can still feel the cooling sensation of mint and the prickling heat of chili peppers or horseradish, but they can no longer perceive complex flavors. People with total anosmia have trouble distinguishing between foods as different as apples and potatoes.

Malnutrition

• As a complete loss of smell leads to an almost total loss of taste, people with anosmia must make a conscious effort to eat sufficient food to stay healthy. The creativity of chefs and the amount of shelf space devoted to novel flavors in supermarkets attest to the sophistication of the human palate. When this refined sense becomes a coarser instrument with which to perceive a meal, diners with anosmia lose much of their interest in food. The desire to eat and enjoy food is so primal that those who lose it risk becoming undernourished and even depressed.

Food Poisoning

• People with total, permanent anosmia must guard against food-borne illnesses more vigilantly than those with an intact sense of smell. Smell evolved in part to alert an animal to the presence of something dangerous or noxious in its food; although the human sense of smell lacks the sophistication of some animals' olfactory capabilities, it does help people decide whether to drink that old milk or pour it out. Without a sense of smell, people with anosmia must rely on visual inspection of foods. Unless a food goes markedly sour, an anosmic person cannot taste spoilage.