A sense of taste is important for health and well-being as alterations to taste can lead to loss of appetite, resulting in malnutrition, affecting both physical and psychological well-being. A wide range of treatment modalities have been used to treat taste disorders.

The aim of this Cochrane review updates was to assess the effects of interventions for the management of patients with taste disturbances.

Methods

Searches were conducted in the Cochrane Oral Health’s Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, CINHAL, AMED, the US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform without restrictions on language or date of publication. Abstracts from scientific meetings and conferences were searched on 25 September 2017. Randomised controlled trials (RCTs) including cross-over trials comparing any pharmacological agent with a control intervention or any non-pharmacological agent with a control intervention were considered.  Standard Cochrane methodological approaches were used for data collection and analysis.

Results

• 10 RCTs involving a total of 581 patients were included.
• 8 RCTs were parallel design, 2 cross-over design.
• 3 trails were considered to have a low risk of bias, 4 a high risk and 3 an unclear risk.
• Only studies on taste disturbances that were idiopathic or resulting from zinc deficiency or chronic renal failure were included.
• 9 trials (544 people) compared zinc supplements to placebo for patients with taste disorders. Two trials involved children and adolescents
• Of these nine trials, 2 trials (119 patients) assessed the patient-reported outcome for improvement in taste acuity using zinc supplements (risk ratio (RR)= 1.40 (95% CI; 0.94 to 2.09) [very low-quality evidence].
• Meta-analysis (3 trials, 366 patients) of taste acuity improvement using objective outcome (continuous data) in idiopathic and zinc-deficient taste disorder patients; standardised mean difference (SMD) = 0.44 (95%CI; 0.23 to 0.65) [very low-quality evidence].
• One cross over trial (14 patients) was analysed separately using the first half of the results for
  • taste detection mean difference (MD) = 2.50 (95%CI; 0.93 to 4.07) [very low-quality evidence].
  • Taste recognition MD= 3.00 (95%CI; 0.66 to 5.34) [very low-quality evidence].
• Meta-analysis (2 trials,292 patients) of taste acuity improvement using objective outcome (dichotomous data) in idiopathic and zinc-deficient taste disorder patients; RR = 1.42 (95%CI; 1.09 to 1.84) [very low-quality evidence].
• 4 of 9 trials using zinc supplementation, reported adverse events like eczema, nausea, abdominal pain, diarrhoea, constipation, decrease in blood iron, increase in blood alkaline phosphatase, and minor increase in blood triglycerides.
• One trial (37 patients) tested taste discrimination using acupuncture, MD = 2.80 (95%CI; -1.18 to 6.78) [very low-quality evidence]. No adverse events were reported in the acupuncture trial.
• None of the included trials could be included in the meta-analysis for health-related quality of life in taste disorder patients.

Conclusions

The authors concluded: –

We found very low-quality evidence that was insufficient to conclude on the role of zinc supplements to improve taste acuity reported by patients and very low-quality evidence that zinc supplements improve taste acuity in patients with zinc deficiency/idiopathic taste disorders. We did not find any evidence to conclude the role of zinc supplements for improving taste discrimination, or any evidence addressing health-related quality of life due to taste disorders.

We found very low-quality evidence that is not sufficient to conclude on the role of acupuncture for improving taste discrimination in cases of idiopathic dysgeusia (distortion of taste) and hypogeusia (reduced ability to taste). We were unable to draw any conclusions regarding the superiority of zinc supplements or acupuncture as none of the trials compared these interventions.

Comments

This Cochrane review is an update of the 2104 review (Dental Elf – 1^st Dec 2014) including 10 trials compared with 9 in the earlier version. The conclusions have changed slightly since the previous version. However,  the available evidence is of very low quality and further high quality RCTs are needed with more clarity and uniformity in the variables.

Links

Primary Paper

Kumbargere Nagraj S, George RP, Shetty N, Levenson D, Ferraiolo DM, Shrestha A. Interventions for managing taste disturbances. Cochrane Database of Systematic Reviews 2017, Issue 12. Art. No.: CD010470. DOI: 10.1002/14651858.CD010470.pub3.

Other references

Cochrane Oral Health Group Blog – Zinc supplements may be effective for taste disorders but more high quality studies are needed

Dental Elf – 1^st Dec 2104

Zinc supplements may have some benefit in treating taste disorders