What is taste loss, and why does it matter?

How would you feel if you could eat food but not taste it? Complete loss of taste is known as ageusia. This affects the tongue’s ability to detect the basic flavours of food. It does not endanger life. But it interferes with the physical and mental well-being of the person.¹ This piece will provide a comprehensive understanding of what taste loss is, its impact on quality of life, available treatments, and precautions to prevent it.

How taste works in the body

The human tongue is a multifunctional organ. It helps with speech and taste. Taste sensation is felt by the taste buds present on the surface of the tongue. The human tongue has three divisions: the anterior, middle, and posterior. The anterior two-thirds and the posterior one-third of the tongue are divided by a groove known as the sulcus terminalis. There are four different papillae, which are tiny projections present on the tongue:² 

• Circumvallate: These are tiny button-like structures present at the back of the tongue. They sense bitterness
• Fungiform: These are mushroom-like projections present at the tip of the tongue and are sensitive to sweetness
• Foliate: These are located on either side of the lateral borders of the tongue and are sensitive to salty and sour tastes
• Filiform: These are hair-like projections present all over the tongue. They usually have nothing to do with tastes

The surface of the tongue has numerous tiny bumps that the naked eye cannot see. They are known as the taste buds. Each of these taste buds has special cells called the taste receptors. When we eat, the food is dissolved by saliva and is attracted by tiny hair-like projections called microvilli found on the taste receptors. Thus, the taste receptor is activated and it sends signals to the nearby nerve ending, from which it reaches the brain through the nerves, and the taste is perceived.²

Different parts of the mouth send signals to your brain using other pathways. The front of your tongue sends signals through one route, the back uses another, and areas like your throat and the flap above your windpipe use a third route. The nerves involved in the taste pathway include the facial, glossopharyngeal, and vagus nerves. These nerves carry signals to the brain that interprets and comprehends the flavours being experienced.²

What causes taste loss?

Taste loss arises from a number of factors. The primary reasons are:

• Infections: Viral infections like COVID-19, bacterial infections causing sore throat, tonsillitis (inflammation of the tonsils), sinusitis, gum and teeth infections, among others¹
• Tobacco usage: Smoking and tobacco usage also contribute to taste loss as they hinder good oral hygiene²
• Tonsillectomy: Removal of tonsils may disturb nerves associated with the taste pathway³
• Neurological damages: Brain stem strokes, nerve injury following a trauma and nerve injury following any surgeries¹
• Drugs: Certain drugs, such as clopidogrel, anaesthetic agents, and psychotropic drugs, are known to cause taste loss on long-term use⁴
• Radiation therapy: People affected by cancer undergo chemotherapy and radiotherapy, which destroys taste buds and causes taste loss^1,2

Signs and symptoms to watch for

How would you feel if you suddenly lost your taste? You cannot enjoy eating at all. The food feels bland and tasteless, even if it looks so appetising. You will start losing interest in eating. Gradually, you will reduce your food intake. As this continues, it will automatically lead to weight loss, malnutrition and psychological disturbances like anxiety at the sight of food, frustration of not being able to taste it, and eventually, depression. Taste loss is often associated with loss of smell (anosmia) and dry mouth (xerostomia).

How doctors check for taste problems

When a person experiences ageusia, it is better to consult a specialist. You can see a dentist or an otolaryngologist. The doctor will obtain a detailed medical history, which includes how the taste loss started, how long this condition has persisted, and other relevant details like the drugs used by the person to rule out the possible causes of ageusia. Any history of surgeries in the head and neck region to rule out any possibility of nerve damage. Any history of stroke must be assessed to rule out brain damage. Physical examination for infections in the head and neck. Neurological examinations are performed to rule out any possible nerve malfunction.¹

Other tests involve blood tests to look for vitamin deficiencies and metal allergies, and neuropsychological tests to avoid confusion between taste loss and smell loss. In case of any brain stem lesions, MRI or additional scans are required. Additionally, gustometry is a special test which is more reliable for testing taste loss. It is of two types. Chemogustometry involves applying special chemicals to different areas of the tongue to check the five different taste perceptions. Electrogustometry involves giving a low-voltage current to stimulate the taste buds on the tongue and elicit a taste response. The next is the spatial testing, which means assessing different areas of the tongue and soft palate for taste responses.⁵ 

How taste loss can be treated

The first step in treating is removing the cause. In case of infections, eliminating the infection will gradually reverse taste loss. For instance, taste loss caused by COVID-19 infection reverses itself within a month or two. In case of dental infections, a proper scaling and treatment of the affected teeth will help restore the taste. For sinusitis, salivary gland infections, and other bacterial infections, antibiotics can help. If it is due to any particular drug, the drug's usage must be stopped. If it is caused by brain stem damage, it requires surgery and other comprehensive management.¹

Reversal of taste loss does not happen overnight. You always have to wait and watch. So it is always better to maintain good oral hygiene. Stay hydrated. Take vitamin and zinc supplements to cope with deficiencies and malnutrition, and eat healthy, even if the food doesn't taste good. Counselling will be of great help for those who are frustrated and depressed because of this condition.¹

What to expect: recovery and follow-up

Start one step at a time. Even if it doesn't taste good, start eating nutritious food for the sake of your health. Experiment with textures such as creamy, crunchy, or soft items. Try foods at different temperatures, like hot soups and ice creams. Experiment with strong tastes like spices. Getting help from a professional may involve counselling to help you with the process. Support from nutritionists, well-planned diets, and nutritional supplements maintains your well-being. Don't miss regular body check-ups. Above all, stay hydrated. Drink plenty of water.^1,2

Special cases to know about

The term ageusia became very common since COVID-19. People started realising that they were losing their sense of taste after the infection. This was very common back then. For most people, it resolved on its own without any intervention. Smell loss also persisted. So smell training was very useful in getting back smell and taste.

The worst part of taste loss is when it is experienced by kids. They do not know how to express it. The most they might say is that their food tastes funny. They start avoiding food, and it eventually takes a toll on their health.

People gradually lose their taste buds as they grow older. Prolonged drug use and other medical conditions also contribute to this. So, it is always better to identify and address the root cause of the condition.

Can taste loss be prevented?

One would never imagine losing taste. It is unpredictable. But it can be prevented. 

Minor lifestyle modifications can contribute a lot. Start with good hygiene. Brush and floss to prevent dental infections, and abstain from tobacco usage or smoking. Eat healthy. Do not miss regular health check-ups. Maintain conditions like diabetes, allergies, and other health issues. All these can prevent taste loss from occurring.^1,2

Summary

Taste is what makes food enjoyable. Losing taste has a lot of hardships, such as being unable to tell if a food is bad. It is always good to look beyond just taste. Do not forget to inspect the expiry dates, textures, or any allergic ingredients in packaged food. These little precautions can prevent the worst from happening. It’s okay to ask for medical help, however and whenever you need it, because losing taste does not mean you have to suffer a flavourless life.