COVID-19, caused by the SARS-CoV-2 virus, impacted millions worldwide. Beyond its respiratory effects, the virus is known for symptoms that can affect various bodily systems. Among these, a notable symptom involves changes to the senses of taste and smell, significantly altering how individuals perceive food.
How Taste and Smell Change
The perception of food flavor is a complex interplay between taste and smell, and COVID-19 can disrupt this in several ways. Anosmia refers to the complete loss of smell, causing foods to taste bland or as if they have no flavor at all, since much of what we experience as “taste” actually comes from aroma. Ageusia is the complete loss of taste, where the tongue is unable to detect basic tastes such as sweet, sour, salty, bitter, and umami.
Dysgeusia, a distorted sense of taste, can make familiar foods taste metallic, chemical, or unpleasant. Individuals might describe water tasting like bleach or chocolate tasting like gasoline. Parosmia involves a distorted sense of smell, where everyday scents, including food aromas, are perceived as foul, rotten, or chemical-like. This symptom can significantly impact eating enjoyment.
Phantosmia is the experience of phantom smells that are not actually present, which can also influence the perception of food. For instance, someone might constantly smell smoke or garbage, which then interferes with how they experience the natural aromas of food. The duration of these sensory changes varies, from a few days to several months or longer. While many recover within weeks, some report persistent issues, including parosmia and phantosmia.
Why COVID-19 Affects Senses
The SARS-CoV-2 virus primarily affects taste and smell by targeting specific cells in the nasal cavity. The virus gains entry into human cells by binding to the angiotensin-converting enzyme-2 (ACE2) receptor and utilizing the TMPRSS2 enzyme for activation. These proteins are expressed in the olfactory epithelium, the tissue lining the nasal cavity responsible for smell.
Research indicates that the virus infects sustentacular cells, which are support cells within the olfactory epithelium, rather than directly infecting the olfactory neurons themselves. These sustentacular cells maintain the health and function of olfactory neurons and help process odors. Damage to these support cells due to viral infection and subsequent inflammation can disrupt olfactory function, leading to smell loss.
While direct infection of olfactory neurons appears less common, inflammation and other neurological pathways may also contribute to changes in taste perception. The disruption of these support cells and the resulting inflammatory response are considered the primary mechanisms behind COVID-19-associated anosmia.
Managing Altered Taste and Smell
When taste and smell are altered by COVID-19, several strategies can help make food more appealing and ensure adequate nutrition. Focusing on the texture and temperature of food can enhance the eating experience, as these senses may remain unaffected. For example, incorporating crunchy elements like nuts or seeds, or varying temperatures with hot and cold components in a meal, can add interest.
Adding strong flavors such as herbs, spices, or acids like lemon or lime juice can also help stimulate remaining taste buds or mask unpleasant perceptions. If foods taste too sweet, adding lemon or lime juice can help mute the sweetness. Maintaining good oral hygiene by brushing teeth and tongue, and rinsing the mouth with solutions like saltwater or baking soda and water, may also help neutralize bad tastes.
To support recovery, “smell training,” also known as olfactory training, is a recommended method. This involves repeatedly smelling a set of four distinct scents, such as rose, lemon, eucalyptus, and clove or cinnamon, twice a day for several weeks to months. This practice aims to stimulate the olfactory nerves, promoting their healing and regrowth. For persistent or severe symptoms, consulting a healthcare professional is advisable to explore further interventions and ensure nutritional needs are met.