The Effectiveness of Zinc Supplementation in Taste Disorder Treatment: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Table 3

Summary of findings.

Zinc supplement compared to placebo for improvement of taste disorder
Patient or population: improvement of taste disorder
Intervention: zinc supplement
Comparison: placebo
Outcomes	Anticipated absolute effects (95% CI)		Relative effect (95% CI)	No. of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with placebo	The risk with zinc supplement
Polaprezinc supplementation in idiopathic and zinc-deficient taste disorder patients, equivalent to (17 mg, 68 mg) of elemental zinc for 12 weeks	454 per 1,000	671 per 1,000 (535 to 839)	RR 1.48 (1.18 to 1.85)	223 (2 RCTs)	⊕⊕⊕⊕ HIGH	Polarprezinc supplementation improved taste disorder in idiopathic and zinc-deficient patients compared with the placebo by 48%, with a CI of 18% to 85% increase in taste acuity
Zinc gluconate supplementation in idiopathic and zinc-deficient taste disorder patients, equivalent to (20 mg, 22.59 mg) per day of elemental zinc for 3-4 months	396 per 1,000	637 per 1,000 (443 to 914)	RR 1.61 (1.12 to 2.31)	102 (2 RCTs)	⊕⊕○○ LOW^a,b	Zinc gluconate supplementation improved taste disorder in idiopathic and zinc-deficient patients compared with the placebo by 61% with a CI of 12% to 131% increase in taste acuity
Zinc picolinate supplementation in idiopathic and zinc-deficient taste disorder patients, equivalent to (28.9 mg) of elemental zinc three times per day for 3 months	444 per 1,000	756 per 1,000 (502 to 1,000)	RR 1.70 (1.13 to 2.56)	73 (1 RCT)	⊕⊕⊕○ MODERATE^c	Zinc picolinate supplementation improves taste disorder in idiopathic and zinc-deficient patients compared with the placebo by 70% with a CI of 13% to 156% increase in taste acuity
Zinc acetate supplementation in patients with taste disorder induced by chronic renal failure, equivalent to (50 mg) per day of elemental zinc for 6 months	0 per 1,000	0 per 1,000 (0 to 0)	RR 26.69 (5.52 to 129.06)	77 (3 RCTs)	⊕⊕○○ LOW^d	Zinc acetate supplementation improved taste disorder in patients with taste disorder induced by chronic renal failure compared with the placebo by 25.69% with a CI of 452% to 128.06% increase in taste acuity

The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RR: risk ratio. GRADE working group grades of evidence. High certainty: We are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: We are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: Our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect. Very low certainty: We have very little confidence in the effect estimate. The true effect is likely to be substantially different from the estimate of effect. a: some concern with random sequence generation and lack of follow-up; b: wide confidence intervals in Heckmann et al. [26]; c: some concern of lack of follow-up; d: very wide confidence intervals in all three included trials.