Taste sensitivity is the capability to perceive and differentiate between flavors like sweet, sour, salty, bitter, and umami. This ability is not uniform and exists on a spectrum, where some individuals experience flavors with great intensity while others perceive them more mildly. This variation in perception is a normal aspect of human biology.
The degree of taste sensitivity can shape an individual’s dietary habits and food preferences. For example, a person with a heightened sensitivity to bitterness might find certain vegetables or dark chocolate to be unpleasantly strong. Conversely, someone with lower sensitivity may not perceive these foods as bitter at all.
The Biological Basis of Taste Perception
The sense of taste, or gustation, originates on the tongue, which is covered in small bumps called papillae. There are three types of papillae that contain taste buds: fungiform, foliate, and circumvallate. A fourth type, the filiform papillae, are the most numerous but do not contain taste buds; instead, they provide friction to help move food. The fungiform papillae are mushroom-shaped and are found mainly on the front two-thirds of the tongue.
Within the papillae are the taste buds, which are clusters of 50 to 100 specialized taste receptor cells. Each taste bud has a small opening called a taste pore, which allows dissolved food molecules, or tastants, to come into contact with the taste receptor cells. The human tongue has between 2,000 and 8,000 taste buds on average. These cells are replaced every 10 to 14 days.
When a tastant binds to a receptor on a taste cell, it triggers a chemical signal. Salty and sour tastes are detected when sodium ions (Na+) or hydrogen ions (H+), respectively, enter the taste cells directly. Sweet, bitter, and umami tastes are detected when molecules bind to G protein-coupled receptors on the surface of the taste cells. This interaction initiates a signaling cascade that ultimately sends a message to the brain.
Nerve signals from the taste receptor cells travel along cranial nerves to the brainstem. From there, the signals are relayed to other brain regions, including the thalamus and the gustatory cortex, where taste perception is processed. This system allows the brain to interpret the chemical information from food and identify it as a specific taste.
Classifying Taste Sensitivity
Individual differences in taste perception are categorized into three main groups: supertasters, medium tasters, and non-tasters. This classification is largely based on the ability to taste a synthetic compound called 6-n-propylthiouracil (PROP), often by placing a coated paper strip on the tongue. To supertasters, PROP has an intensely bitter taste, while medium tasters perceive it as moderately bitter, and non-tasters find it virtually tasteless.
These variations in taste sensitivity are linked to both anatomical and genetic factors. Supertasters tend to have a higher density of fungiform papillae on their tongues, the small bumps that house taste buds. This increased number of papillae means they have more taste receptors, leading to a more intense perception of flavors. It is estimated that supertasters make up about 25% of the population, with medium tasters accounting for 50%, and non-tasters the remaining 25%.
Genetics also plays a part, particularly the TAS2R38 gene, which codes for a bitter taste receptor. There are two common variations of this gene: one that is sensitive to PROP (PAV) and one that is not (AVI). Individuals who inherit two copies of the sensitive allele (PAV/PAV) are supertasters, while those with two non-sensitive alleles (AVI/AVI) are non-tasters. Heterozygous individuals, who have one of each allele (PAV/AVI), are medium tasters.
Influence on Food Preferences and Diet
A person’s classification as a supertaster, medium taster, or non-taster directly impacts their food choices and dietary patterns. Due to their heightened sense of taste, supertasters often perceive the bitterness in certain foods as overwhelming. This can lead to an aversion to cruciferous vegetables like broccoli and kale, as well as grapefruit and coffee.
The increased sensitivity of supertasters extends beyond bitterness. They may also be more sensitive to the burn of capsaicin in chili peppers, the richness of high-fat foods, and the sweetness of sugar. This can result in a diet lower in fat and sugar, but also potentially lacking nutrients from some bitter-tasting vegetables.
In contrast, non-tasters have a higher threshold for detecting flavors and may find that foods need more seasoning, sugar, or fat to be palatable. This can lead to a preference for highly processed foods. Their reduced sensitivity to bitterness means they are more likely to enjoy a wider variety of vegetables, but their dietary quality may be lower if they seek out intensely flavored, less nutritious options.
Medium tasters fall between these two extremes and have a more balanced perception of flavors. Their food preferences are less influenced by their taste sensitivity compared to supertasters and non-tasters.
Factors That Alter Taste Perception
An individual’s baseline taste sensitivity is not static and can be altered by various internal and external factors. Both internal and external conditions can change how flavors are perceived. Some of the primary factors include:
- Aging, as the number of taste buds can decrease and the remaining ones may become less sensitive.
- Illness, as viral infections like the common cold, influenza, and COVID-19 can cause a temporary loss or alteration of taste.
- Medical treatments, including chemotherapy and radiation therapy, which can damage taste receptors and affect how food tastes.
- Medications, as some antibiotics and antidepressants can have side effects that alter taste perception.
- Smoking, which can dull the sense of taste by altering the structure of taste buds.
- Nutritional deficiencies, particularly a lack of zinc, which has been linked to taste disorders.
- Poor oral hygiene and dental problems, which can also contribute to changes in taste.