What Are Taste Buds? 5 Basic Tastes

The average tongue has somewhere between 5,000 and 10,000 taste buds.

When food dissolves in your saliva, it activates receptors at the tips of the cells that can distinguish between different types of tastes. The receptors then send signals to the brain, relaying the precise flavor you are experiencing.

Most of your taste buds are found in papillae (small, rounded bumps on the upper surface of the tongue). Taste buds can also be found on the roof of the mouth and at the back of the throat, which are replaced with new taste buds every 8 to 12 days.

There are four types of papillae on the tongue:

1. Fungiform papillae: These have a slight mushroom-like shape and are mostly found at the apex (tip) of the tongue and on the sides. The facial nerve innervates it.
2. Filiform papillae: These are thin, long V-shaped papillae cones that lack taste buds but are the most numerous. These papillae are mechanical and do not participate in gustation.
3. Foliate papillae: Ridges and grooves found on the lateral margins of the tongue toward the back of the tongue. The facial nerve (anterior papillae) and the glossopharyngeal nerve (posterior papillae) innervate it.
4. Circumvallate papillae: Dome-shaped structures on the tongue that range from 8 to 12. They are located on the back surface of the tongue, and each contains over 100 taste buds.

For a long time, scientists believed that each taste was identified at a different location on the tongue. However, subsequent research has proven this to be false. Although the edge of the tongue has more taste buds than the base and is more sensitive, the tongue does not have different areas of taste. The bitter taste is an exception because it is mostly found at the back of the tongue.

The basic tastes that are universally accepted are as follows:

1. Sweet: Sweet is a pleasurable taste that indicates the presence of sugar. Sweet complements the other basic tastes well.
2. Salt: The salt receptor is the most basic taste receptor in the mouth. When you reduce your salt intake, your taste buds can adjust and adapt to be satisfied with less. Adding salt to traditionally sweet dishes as a flavor enhancer is necessary to amplify the sweet notes. Most baked dessert recipes include a pinch of salt.
3. Sour: Your tongue can detect the sour acidity of citrus fruits, such as lemons and oranges. Fermented foods, such as sauerkraut and yogurt can also have a sour taste.
4. Bitter:  This is the most delicate of the five flavors. Many bitter compounds are toxic, which is why many people find bitter flavors unpleasant.
5. Umami: This flavor is sometimes described as savory or meaty. It is the most recent and widely recognized of the basic tastes. This flavor is distinguished by the presence of glutamic acids, such as in soy sauce and monosodium glutamate.

Your taste buds can also detect fatty, alkaline, and metallic tastes. Because fats are an important part of a healthy diet, there could be taste buds that are particularly sensitive to fatty flavors. The alkaline taste is derived from briny foods or liquids and is thought to be the opposite of sour. However, no conclusive research on these tastes exists.

Each taste receptor on the tongue is specialized to recognize different tastes. They have microscopic hair-like proteins called microvilli that attach to certain chemical compounds according to their taste type. Scientists are still working out how chemicals fit into the receptors.

Deep inside the tissue of the tongue, these cells link to taste-related neurons, which connect them to the rest of the nervous system.

• Food breakdown: Your tongue breaks down food into its chemical-building components. Larger components are physically broken down by your teeth, and your saliva includes enzymes that break down these fragments into molecules.
• Chemical involvement: Once these basic food molecules start floating about the tongue, they wash over the papillae and reach the taste receptors. The microvilli of the taste receptors only interact with substances that match their taste specialty. 
• Signals to the brain: Taste receptor cells activate their separate neurons after binding to a food molecule. These provide acute electrical impulses to the brain, alerting it to the presence of certain flavors on the tongue. They eventually level out when the receptor cells get used to the taste, and the brain correctly interprets it.
• Olfactory sensors: Chewing produces gaseous food chemicals, which move through the back of the mouth and into the nasal cavity. Olfactory sensors then communicate to the brain more complex flavor profiles than the five basic tastes.
• Information: Taste receptors signals reach the lower brain stem. They are then grouped and enter the conscious brain.

When the enhanced taste impulses reach sensory perception parts of the brain, they join with smell signals to inform the brain about what's in the mouth. If the brain sees the overall flavor as good, it will stimulate the production of saliva and stomach secretions, facilitating digestion and making certain foods more appetizing.

Every couple of weeks, your taste buds die and regenerate. Sometimes, this can occur more frequently because of their vulnerable position in the mouth. Causes of change in taste buds include:

• Trauma: Every time you burn or bite your tongue, you effectively eliminate some taste buds although they may regenerate quickly. 
• Age: Age affects how frequently your taste buds turn over. As you age, your body slows down regenerating cells, including taste and smell receptor cells. According to recent studies, a change or loss of taste may begin at about age 60.
• External factors: Taste buds can die as a result of external factors, such as taking certain medications or undergoing chemo or radiation. However, they should return once the treatment is completed.

Anosmia is a medical condition in which a person experiences a partial or complete loss of smell. In most cases, loss of taste is associated with loss of smell. It is uncommon for someone to “lose” their sense of taste. Typically, swelling and excessive mucus buildup in the sinuses block the nerve endings deep within the nose that detect odors. Because the senses of smell and taste are so inextricably linked, people often report their symptoms as a loss of taste.

Possible causes of loss of taste and smell include:

• COVID-19: One of the most reported COVID-19 symptoms is a loss of taste and smell. Although studies are underway to investigate why and how this occurs, it is thought that the virus temporarily disrupts the olfactory receptors in the nasal lining, resulting in a loss of taste and smell.
• Upper respiratory infection: The onset of an upper respiratory tract infection (URTI) can cause inflammation and a buildup of excess mucus throughout your nose, throat, pharynx, larynx, and bronchi, which can affect your taste. Many factors can cause URTIs, including the common cold, influenza, or another bacterial or viral infection.
• Allergies (hay fever), sinusitis (sinus infection): Due to increased inflammation and mucus in the nasal cavities, both allergy-related nasal congestion and sinus infections can cause a loss of taste and smell.
• Other possible causes:
  • Nasal polyps
  • Medications
  • Dental problems
  • Cancer treatment
  • Alzheimer’s disease
  • Multiple sclerosis
  • Parkinson’s disease
  • Head injuries or trauma
  • Vitamin and nutrient deficiencies (especially zinc)

There are several possible causes for someone to lose their sense of taste and smell, but most people regain their senses after the underlying causes are addressed. However, if your symptoms persist or you suspect your loss of taste and smell is caused by a more serious condition, seek medical attention immediately.

In many cases, loss of taste is a symptom of an underlying issue that can be resolved once you treat the primary condition. Tips for getting your taste buds back include the following:

• Get plenty of rest and drink plenty of warm fluids.
• Stay hydrated to reduce inflammation and dilute excess mucus buildup caused by an upper respiratory or sinus infection.
• Use a nasal spray to help clear out your sinuses and reduce mucus buildup.
• If you have a cold, flu, or allergies, take over-the-counter or prescription medications.
• Practice proper oral hygiene to maintain a healthy sense of taste.

These treatments can help regain the sense of smell and taste by temporarily reducing the amount of congestion that is blocking your smell sensors (the olfactory sensory neurons), which are located high inside the back of your nose.

Types of taste disorders

• Hypogeusia: Partial loss of taste
• Ageusia: Total loss of taste 
• Dysgeusia: Taste distortion that may include an unpleasant or metallic taste.

Causes of taste disorders

Taste disorders are commonly caused by an injury or illness, but they can also be present at birth. Other factors include:

• Head injury, 28%
• Radiation therapy, 12%
• Chemical exposure, 24%
• Surgeries to the ear, nose, and throat, 5%
• Poor oral hygiene and/or dental problems, 9%
• Upper respiratory and/or middle ear infection, 12%

Treating taste disorders

• Discontinuing or changing a medication that is causing the issue
• Treating the underlying medical condition
• If your taste disorder cannot be adequately treated, counseling may help you adjust to your situation