Table 1.
The main patient characteristics of the included studies.
| Author (s), year (study duration) | Country | Study type | Total no. of patients | No. of patients receiving zinc | No. of patients receiving placebo | Gender | Age (year) | Zinc supplement | Disease or case-induced taste disorder |
|---|---|---|---|---|---|---|---|---|---|
| Ikeda et al., 2013 [23] (12 weeks) | Japan | Double-blind RCT w/placebo | 219 | 108 | 111 | 87 M and 132 F | Average for intervention: 43.3 Control: 47.1 |
Polaprezinc, 34 mg/d | Zinc deficiency and idiopathic taste disorder |
| Sakagami et al., 2009 [24] (12 weeks) | Japan | Double-blind RCT w/placebo. Multicentre | 109 | 81 | 28 | M and 56 F 51 | 20–80 | Polaprezinc, (group 1) 17 mg (n = 27), (group 2) 34 mg (n = 26) or (group 3) 68 mg (n = 28) daily | Idiopathic taste disorder |
| Stewart-Knox et al., 2007 [25] (6 months) | Japan | Double-blind RCT w/placebo | 199 | NR | NR | 103 M and 96 F | 70–78 | Zinc gluconate, elemental zinc gluconate (group 1) 15 mg/d and (group 2) 30 mg/d | Idiopathic taste disorder in elderly people |
| Heckmann et al., 2005 [26] (3 months) | Germany | RCT w/placebo | 50 | 24 | 26 | 7 M and 43 F | 41–82 | Zinc gluconate (140 mg/d, equivalent to 20 mg/d of elemental zinc) | Idiopathic taste disorder |
| Matson et al., 2003 [27] (6 weeks) | UK | Double-blind RCT w/placebo | 24 | 12 | 12 | M and F | 30 to 72 | Zinc sulphate | Chronic renal failure |
| Sakai et al., 2002 [28] (3 months) | Japan | Double-blind RCT w/placebo | 73 | 37 | 36 | M/NR and 47 F | 23–79 | Picolinate, 28.9 mg of elemental zinc three times/d | Zinc deficiency and idiopathic taste disorder |
| Yoshida et al., 1991 [29] (4 months) | Japan | Double-blind RCT w/placebo | 52 | 28 | 24 | M to F ratio was 1 : 1.8 | Mean age for group 55.1 & 59.2 for placebo | Zinc gluconate, 158 mg zinc gluconate; zinc content: 22.59 mg | Zinc deficiency and idiopathic taste disorder |
| Mahajan et al., 1982 [30] (6 months) | USA | Double-blind RCT w/placebo | 24 | 12 | 12 | Only males | Treatment 46 ± 8 Control 49 ± 12 |
Zinc acetate, zinc acetate (50 mg of elemental zinc/d) | Chronic renal failure |
| Mahajan et al., 1980 [31] (6 months) | USA | Double-blind RCT w/placebo | 22 | 11 | 11 | NR | Treatment: 51.3 ± 3.2 Control: 55.1 ± 2.8 |
Zinc acetate, zinc acetate (50 mg of elemental zinc/d) | Chronic renal failure |
| Mahajan et al., 1979 [32] (6 months) | USA | Double-blind RCT w/placebo | 31 | 11 | 20 | NR | NR | Zinc acetate, zinc acetate (50 mg of elemental zinc/d) | Chronic renal failure |
| Atkin-Thor et al., 1978 [33] (6 weeks) | USA | Double-blind crossover RCT w/placebo | 29 | 20 | 9 | NR | 21–70 | Zinc sulphate, 440 mg ZnSO4 postdialysis, 3 times per week | Chronic renal failure |
| Henkin et al., 1976 [34] (6 months) | USA | Double-blind crossover RCT w/placebo | 106 | Not clear | Not clear | 53 M and 53 F | 19–84 | Zinc sulphate, 100 mg of zinc ion in four oral doses | Idiopathic taste disorder |
NR: not reported, M: male, F: female, RCT: randomized controlled trial, w: with.