Thousands of taste buds are located on the tongue, but some are also scattered on the roof of the mouth, inside the cheeks, and in the upper throat. Each bud contains 50 to 150 specialized taste receptor cells, which send nerve signals to the brain about the five major tastes—sweet, sour, bitter, salty, and umami (often described as savory). What’s more, though the words taste and flavor are often used interchangeably, flavor goes beyond taste and depends largely on the smell of foods. Take chocolate ice cream. Your taste buds perceive that it's sweet, but it's the aromatic chemicals reaching your nose that tell you it's chocolate and not another flavor.
Humans vary genetically in their perception of tastes and have different thresholds for perceiving flavors. About one-quarter of the population, mostly women, are supertasters—they experience tastes more intensely, largely because they have extra taste buds. For instance, supertasters are especially sensitive to bitter compounds in some vegetables and artificial sweeteners. Another quarter of people (unfairly dubbed non-tasters) have far fewer taste buds than average and are often “blind” to such bitter tastes, as well as to some other tastes and flavors. Cultural or psychological factors also shape how food tastes to people.
All mammals prefer sweetness from birth and dislike bitterness, possibly because many poisonous plants contain bitter compounds. Still, some research suggests that a high intake of sugary foods (especially soft drinks) increases the attraction to sweetness. The enjoyment of bitter foods and beverages is usually an “acquired” taste, meaning it takes time to overcome the initial dislike.
It's learned, like most taste preferences. People who consume lots of salt from a young age develop a tolerance to it and consequently may even crave it. But what is learned can be unlearned: People who go on a low-sodium diet find that they adjust to it after about six to eight weeks. That is, they actually change the threshold at which they detect salt.
But the nerve receptors within taste buds, which live only one to two weeks, are replaced more slowly as you age. Moreover, certain chronic illnesses (such as diabetes) and medications can damage taste buds or nerves, while oral conditions (such as dry mouth or dentures) can prevent food chemicals from activating taste buds. In addition, taste sensitivity is often impaired by age-related neurological changes. Such losses can be dangerous. For example, familiar flavors may become distorted and seem unpleasant, leading some older people to eat less and become malnourished. Others start eating more sweets, or overseason with salt or sugar.
First, you should consult your health care provider to see if there’s a treatable underlying problem behind your loss. If not, there are things you can do to compensate, such as chewing food well to boost saliva release and better distribute the chemicals in foods to the taste buds. You can also choose stronger-tasting foods, use more spices and herbs (not salt and sugar), and concentrate on contrasts in texture, temperature, and flavor. There are several cookbooks focusing on flavorful recipes that can help you make up for losses in the sense of taste.