What causes impaired sense of taste (hypogeusia)?

From the Guidelines

Impaired sense of taste (hypogeusia) can be caused by numerous factors, including zinc deficiency, which is a significant and often underdiagnosed condition that can lead to impaired taste function, as evident from the espen micronutrient guideline published in 2022 1. The causes of hypogeusia are multifaceted and can be attributed to various factors, including:

• Viral infections, such as COVID-19, which has been reported to cause anosmia and dysgeusia in several studies, including a systematic review of the literature, case series, and recommendations for clinical assessment and management published in 2020 1
• Medications, such as antibiotics, antidepressants, antihistamines, and chemotherapy drugs, which can affect taste perception
• Aging, which naturally reduces taste bud sensitivity, typically beginning around age 60
• Smoking, which damages taste buds and reduces taste sensitivity
• Nutritional deficiencies, particularly zinc, vitamin B12, and copper, which can significantly impair taste function
• Medical conditions, such as Sjögren's syndrome, Bell's palsy, head trauma, radiation therapy to the head and neck, dental problems, and neurological disorders like Parkinson's disease or Alzheimer's disease
• Poor oral hygiene, dry mouth (xerostomia), and structural issues affecting the tongue or nasal passages, which can also contribute to taste impairment It is essential to address the underlying cause of hypogeusia, which may include stopping or changing medications, treating infections, improving nutrition, quitting smoking, or managing chronic conditions. Some key points to consider in the management of hypogeusia include:
• The importance of zinc supplementation in patients with zinc deficiency, as highlighted in the espen micronutrient guideline 1
• The need for early recognition and treatment of viral infections, such as COVID-19, to prevent long-term taste impairment 1
• The potential benefits of quitting smoking and improving oral hygiene to reduce the risk of taste impairment
• The importance of managing chronic conditions, such as neurological disorders, to prevent taste impairment and other complications.

From the Research

Impaired Sense of Taste (Hypogeusia)

Impaired sense of taste, also known as hypogeusia, refers to a diminished sense of taste. Several conditions can cause hypogeusia, including:

• Zinc deficiency 2, 3
• Side-effects of drugs 4, 3
• Neurological disorders, such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) 4
• Lesions of the lingual epithelium 3
• Neurological impairment 3
• Pharmacological effects 3
• Aging 5
• Exposure to chemicals 2, 5
• Trauma 5
• High alcohol consumption 5
• Cigarette smoking 5
• Poor oral health 5
• Malnutrition 5
• Viral upper respiratory infections, including influenza 6, 5 and COVID-19 5

Diagnostic Approaches

Diagnosing hypogeusia involves:

• Careful evaluation of dietary elements 2
• Assessment of hereditary disorders 2
• Evaluation of the type of work and contact with pollutants known to be related to dysgeusia 2
• Physical examination, including a meticulous review of the oropharynx 2
• Determination of the levels of perception and identification of flavors using the forced scale triple choice technique 2
• Measurement of serum and urinary levels of zinc using a flameless atomic absorption spectrophotometer 2

Potential Implications

Hypogeusia can lead to:

• Appetite loss 5
• Changes in eating habits 5
• Potential effects on health, including nutritional disorders and wasting in chronic liver disease, cancer, or human immunodeficiency virus infected patients 3