Introduction

Our sense of taste is composed of five basic flavours: sweet, sour, salty, bitter and umami. We rely on the range of our palate to help us enjoy food. A person with Ageusia experiences a total loss of taste, and there are various causes for this, including damage to taste buds, nerves or regions of the brain that affect taste perception. This condition can be mistaken for other taste disorders, such as:

• Hypogeusia: a reduction in taste sensitivity where a person experiences less intense taste sensations
• Dysgeusia: the distortion of taste, which can be unpleasant and metallic
• Phantom taste perception- when a person can have the sensation of taste without any stimulus

Taste is a crucial part of our memories, survival, and social lives, as it can isolate people in social settings. Memories linked to taste can no longer be accessed and can impact a person’s identity. Furthermore, the lack of taste and sensation can lead to unintended weight loss and malnutrition. In this article, we will explore ageusia's impact on the mental and physical well-being of a person.

Biological mechanisms of taste

Taste plays a central role in our daily lives. It is crucial for our social, mental and nutritional well-being. In a more scientific context, taste is the biological process that allows us to perceive different flavours. The sensation of taste is triggered by chemical substances in food that interact with specialised sensory cells found in our taste buds. ¹  

Taste buds on our tongue are the sensory organ that allows us to taste.. They contain many sensory cells which are connected to different nerve fibres. These sensory cells form a capsule with an opening at the top. At the opening, thin extensions of the cells called taste hairs or microvilli are found. The proteins on the taste hairs bind to any taste-producing substances at the cell surface.¹     

There are three nerves, called the VII, IX and X cranial nerves, which carry taste information from the tongue to the gustatory cortex of the brain. There, the gustatory nucleus processes these impulses, integrating them with smell and visual cues to create the perception of flavour and pleasure from food.¹  

Ageusia can arise through the disruption of tasting pathways starting at the taste buds. Medical treatments, such as chemotherapy, radiotherapy and other cancer treatments, may alter taste bud cells or cause cell death. During these cancer treatments,  salivary glands can also become damaged, preventing saliva from transporting stimulating proteins to the taste hairs. As a result, a person can lose their sense of taste entirely.²

Inflammation or infection near any taste buds can trigger death of taste bud cells and taste hairs. This would lead to a reduction in taste bud cells and disrupt the taste hairs’ ability to detect stimulants. Additional lesions due to inflammation in the central taste pathway, including the cranial nerves, can further contribute to the development of ageusia. 

Taste is linked to our other senses; therefore, any intervention in other areas of the body can impact taste perception, such as:

• Ear surgery 
• Laryngoscopy - examination of the voice box 
• Any dental surgical treatment²

This is because these procedures can lead to infection and/or trauma of the chorda tympani nerve, which is another nerve essential in transporting gustatory cues picked up at the tongue. 

Furthermore, autoimmune diseases can alter and distort the taste systems within taste buds. This includes diseases such as;

• Hypertension - high blood pressure 
• Diabetes 
• Liver disorder 
• Hyperthyroidism - an overactive thyroid gland 
• Sjögren syndrome -  the body attacks its own glands that produce fluid, such as tears and saliva.

Lastly, age is another factor in the development of ageusia, as there is a normal decline in taste perception as age increases.² However, total loss of taste is rare. Elderly patients are affected by other conditions that contribute to ageusia, such as;

• Dietary deficiency 
• Secondary complications of oral disease 
• Central nervous system complications in diseases like:
  • Alzheimer’s
  • Parkinson’s 
  • Bell’s Palsy
• Polypharmacy - taking two or more medications at the same time²

Psychological consequences of ageusia

The loss of taste is psychologically distressing. It opens up several pathways for mental disorders to develop. The sense of taste is closely linked to emotions and memory, which can be affected by ageusia. As a result, an ageusic person may end up feeling disconnected from their surroundings and themselves.  

A significant consequence of ageusia is anhedonia. Anhedonia is a psychological condition where the patient loses the ability to derive pleasure from normally pleasurable activities, such as eating. It is closely linked to the loss of smell, which may be another factor in ageusia development. In other words, a person would be less motivated to eat or drink if they know that the experience will not be enjoyable for them.³

There is a significant link between the loss of taste and depression. Food and drink are a major contributing factor to how people form bonds in social settings. People with ageusia may no longer enjoy social gatherings as much and, therefore, could end up feeling depressed. This can further impact a person’s concentration and work ethic, affecting their educational and professional life.³

Our ability to taste food and drink is closely linked to a person’s identity, memory and culture. Without taste, the memories and experiences that make up a person's individuality can no longer be accessed. This can be detrimental to mental health, often leaving a person hopeless and frustrated. It is very easy to take the sensation of taste for granted and not fully grasp the importance it holds in our lives.³

Nutritional consequences of ageusia

Several nutritional consequences come with ageusia. People with ageusia drastically change their dietary habits. An example of this is that to counter the lack of taste, patients overcompensate by adding excessive sugar or salt. This can lead to increased weight gain and consequently the development or intensification of hypertension, heart disease or diabetes.²

Patients may also lose the ability to determine if they are full due to the loss of taste signals, further contributing to weight gain and other unnecessary health issues. 

A person can become malnourished due to the loss of joy from eating, as a decreased appetite and reduced food intake lead to insufficient calories and nutrient intake. This can lead to muscle atrophy and decreased physical function. A food deficit can also lead to zinc deficiency, further altering taste perception. Additionally, a reduced nutrient intake puts the body’s immune system at risk, hence, worsening any existing medical conditions.²

Coping strategies and interventions

Dealing with ageusia can be challenging to come to terms with. However, there are ways to cope with and treat this condition. Treatments aim to relieve the distressed psychological state and improve the quality of life for patients. 

The original cause of ageusia determines the therapeutic steps taken. If it arises from chemotherapy and other medications, then it is potentially reversible. However, it may not be possible for a patient to stop their cancer treatment or discontinue their drugs. To combat this, zinc supplements are prescribed, which may restore taste. 

It is also recommended to keep the mouth moist, as saliva is important for taste, and to avoid smoking or tobacco in general. These products often dampen taste buds and lead to dry mouth. 

Patients can do their best to reduce their risk of infection and make oral hygiene a priority. This is to minimise damage to the taste perception regions in the mouth, nose and brain. However, there is no specific therapy available for existing physical trauma to the nerve supply. 

Nutritional support can be provided, such as recommending patients to eat small but frequent meals and use condiments to enhance flavour to substitute for the taste of salt and sugar. Trying different textures and acidities in food can help stimulate the appetite. As we know, taste is linked to smell and visual presentation. Making food aromatic and visually appealing increases the joy of eating. 

Research and future directions

Clinicians often overlook ageusia. Therefore, it is important to have a dynamic team of healthcare professionals to manage a patient and their case of ageusia. Clinicians should consult with pharmacists to check if medications prescribed risk ageusia. There has been an effort to increase awareness among clinicians, pharmacists and nurses of the frequency of ageusia in patients. However, all they can currently do is improve hydration and use artificial saliva. 

Continuous research is being done to develop a better understanding of the nature and frequency of ageusia and its consequences on the psyche and diet. Further research must be done to improve diagnosis using gustatory dysfunctions as indicators. It is crucial to reduce morbidity in patients as a result of ageusia, and to achieve this, there must be clear and open communication between research and healthcare professionals to find the best route of diagnosis, management and treatment for individual cases.  ²

Summary 

Ageusia is the complete loss of taste, often caused by neurological conditions, infections (like COVID-19), or medications. Taste is crucial for pleasure, appetite regulation, and social connection. Psychological effects include loss of enjoyment in eating, increased risk of depression and anxiety, and disconnection from cultural or personal identity. Nutritional consequences include decreased appetite and risk of malnutrition, craving overly salty, sugary, or fatty foods to compensate, and potential weight loss or unhealthy eating patterns. People may cope through enhancing food texture, temperature, and umami, nutritional guidance and mental health support, and exploring alternative sensory pleasures (e.g., visuals, aroma). A holistic care approach is essential when addressing both physical and emotional aspects of living with ageusia.