Holding the nose when eating often makes food less flavorful. While it is possible to distinguish whether chocolate is bitter or sweet, the candy does not have the familiar chocolate flavor. Similarly, the coffee flavor is largely dependent on smell.
Both smell and taste are part of the human chemical sensing system. Foods release molecules that stimulate nerve cells found in the mouth, throat and nose. Holding the nose prevents the nerve cells inside from detecting these smells.
The tongue has taste buds for sweet, sour, bitter and salty. However, the brain combines signals from the taste buds, smells, textures and temperature to sense the flavor of foods.
Some people are born with a poor sense of smell, while others lose the ability to sense odors due to disease or dental problems. Prolonged exposure to certain chemicals also affects the sense of smell and, ultimately, the taste of food.
A loss of the sense of smell decreases the desire for many older people to eat. The sense of smell alerts people to dangers, including fire, spoiled food and poisonous fumes. Losing the sense of smell is like holding the nose when eating, but it lasts much longer. An adult's sense of smell begins to decline after age 60, and men tend to have a less-accurate sense of smell than women.