. 2020 Apr 27;103(1):86–99. doi: 10.4269/ajtmh.19-0718

Table 2.

Study characteristics

Study (author, year [Ref.])	Country	Population	% Men	Mean age (SD) (years)	Intervention duration	Micronutrient form	Dosage (per capsule/tablet/lozenge); dosing schedule	Outcomes reported
Vitamins A and E (two studies)
Hemila²⁷	Finland	19,791	100	I: 57.2 C: 57.1	6.1 years	dL-α-tocopherol acetate	50 mg; NR	Self-reported cold incidence
Hemila²⁷	Finland	19,791	100	I: 57.3 C: 57	6.1 years	Water-soluble β-carotene beadlets	20 mg, NR	Self-reported cold incidence
Hemila²⁸	Finland	26,148	100	I: 57.2 C: 57.1	6.1 years	dL-α-tocopherol acetate	50 mg; NR	Clinical pneumonia incidence
Hemila²⁸	Finland	26,148	100	I: 57.3 C: 57	6.1 years	Water-soluble β-carotene beadlets	20 mg, NR	Clinical pneumonia incidence
Vitamin D (eight studies)
De Gruijl²⁹	The Netherlands	70	8.6	I: 21.9 (2.3) C: 21.5 (2.1)	2 months	Vitamin D3	1 000 IU; 1 capsule daily	Self-reported cold incidence
Goodall³⁰	Canada	600	36.3	I, C: 19	2 months	Vitamin D3	10,000 IU; 1 capsule weekly	Self-reported and laboratory-confirmed cold incidence
								Cold duration
								Subjective symptom severity per cold episode
Laaksi³¹	Finland	164	100	I, C: 18–28^*	6 months	Vitamin D3	400 IU; 1 capsule daily	Self-reported cold incidence
Li-Ng³²	United States	148	20.3	I: 59.3 (13) C: 58.1 (13.4)	3 months	Vitamin D3	2 000 IU; 1 capsule daily	Self-reported and laboratory-confirmed URTI incidence
								URTI duration
								Subjective symptom severity per URTI episode
Murdoch³³	New Zealand	322	25.2	I: 47 (10) C: 48 (10)	18 months	Vitamin D3	200,000 IU (first 2 months) and 100,000 IU (subsequent months); 1 capsule monthly	Self-reported URTI incidence
								URTI duration
								Subjective symptom severity per URTI episode
Rees³⁴	United States	759	57.7	I: 60.7 (6.7) C: 60.5 (6.4)	18 months	Vitamin D3	1 000 IU; 1 capsule daily	Self-reported cold incidence
Rees³⁴	United States	759	57.7	I: 60.7 (6.7) C: 60.5 (6.4)	18 months	Vitamin D3	1 000 IU; 1 capsule daily	Cold duration
Shimizu²⁶	Japan	215	30.7	I: 52.8 (6.2) C: 52.6 (67)	5 months	Vitamin D3	400 IU; 1 capsule daily	Self-reported URTI incidence
								URTI duration
								Subjective symptom severity per day while sick
Simpson³⁵	Australia	34	41.2	I: 35 (12.5) C: 30.3 (11.8)	5 months	Vitamin D3	2 000 IU; 1 capsule daily	Self-reported and clinically diagnosed ARI
								Incidence
								ARI duration
								Subjective symptom severity per ARI episode
Zinc (10 studies)
Douglas³⁶	Australia	63	42.9	I: 30 C: 35.6	Until symptom resolution (min: 3 days; max: 6 days)	Zinc acetate	10 mg ^‡; 1 lozenge every 2 hours while awake and between 6 and 8 lozenges daily	Cold duration
Douglas³⁶	Australia	63	42.9	I: 30 C: 35.6	Until symptom resolution (min: 3 days; max: 6 days)	Zinc acetate		Subjective symptom severity per cold episode
Eby³⁷	United States	65	53.8	I: 35.6 (2.2) C: 28 (2.8)	Until symptom resolution	Zinc gluconate	23 mg; 2 tablets initially and followed by 1 tablet every 2 hours while awake (≤ 12 tablets daily)	old duration
Eby³⁷	United States	65	53.8	I: 35.6 (2.2) C: 28 (2.8)	Until symptom resolution	Zinc gluconate		Subjective symptom severity per cold episode
Godfrey³⁸	United States	73	60.3	I: 21.2 ^† C: 20.1 ^†	Until symptom resolution	Zinc gluconate trihydrate	23.7 mg; 1 lozenge every 2 hours (≤ 8 lozenges daily)	Cold duration
Godfrey³⁸	United States	73	60.3	I: 21.2 ^† C: 20.1 ^†	Until symptom resolution	Zinc gluconate trihydrate	23.7 mg; 1 lozenge every 2 hours (≤ 8 lozenges daily)	Subjective symptom severity per day while sick
Mossad³⁹	United States	99	19.2	I: 37.5 (7.5) C: 37.9 (9.2)	Until symptom resolution	Zinc gluconate	13.3 mg; 1 lozenge every 2–3 hours while awake	Cold duration
Mossad³⁹	United States	99	19.2	I: 37.5 (7.5) C: 37.9 (9.2)	Until symptom resolution	Zinc gluconate	13.3 mg; 1 lozenge every 2–3 hours while awake	Subjective symptom severity per day while sick
Petrus⁴⁰	United States	101	46.5	I, C: 26.5	Until symptom resolution (max: 14 days)	Zinc acetate	9 mg ^‡; 1 lozenge every 1.5 hours while awake (first day) and then every 2 hours while awake (on following days with symptoms)	Cold duration
								Subjective symptom
								severity per day while sick
Prasad⁴¹	United States	48	37.5	I: 36.4 (11.1) C: 37.8 (10.9)	Until symptom resolution	Zinc acetate dihydrate	42.96 mg; 1 lozenge every 2–3 hours while awake	Cold duration
Prasad⁴¹	United States	48	37.5	I: 36.4 (11.1) C: 37.8 (10.9)	Until symptom resolution	Zinc acetate dihydrate	42.96 mg; 1 lozenge every 2–3 hours while awake	Subjective symptom severity per day while sick
Prasad⁴²	United States	50	32	I: 34.5 (14.06) C: 35.9 (13.4)	Until symptom resolution	Zinc acetate	13.3 mg; 1 lozenge every 2 hours while awake	Cold duration
Prasad⁴²	United States	50	32	I: 34.5 (14.06) C: 35.9 (13.4)	Until symptom resolution	Zinc acetate	13.3 mg; 1 lozenge every 2 hours while awake	Subjective symptom severity per day while sick
Turner⁴³	United States	279	NR	NR	Until symptom resolution (min: 3 days; max: 6 days)	Zinc acetate	5 mg; 1 lozenge every 2–3 hours while awake (≤ 6 lozenges daily)	Cold duration (median)
						Zinc acetate	11.5 mg; 1 lozenge every 2–3 hours while awake (≤ 6 lozenges daily)	Cold duration (median)
						Zinc acetate		Subjective symptom severity per day while sick
						Zinc gluconate	13.3 mg; 1 lozenge every 2–3 hours while awake (≤ 6 lozenges daily)	Subjective symptom severity per day while sick
Veverka⁴⁴	United States	30	80	I: 18.5 (0.89) C: 18.6 (0.82)	Supplementation: 7 months	NR	15 mg; 1 tablet daily	Self-reported and clinically diagnosed cold incidence
Weismann⁴⁵	Denmark	130	NR	I, C: 18–65^*	Until symptom resolution (max: 100 days)	Zinc gluconate	31.3 mg; 1 lozenge every 1–1.5 hours while awake (≤ 10 lozenges daily)	Cold duration
								Subjective symptom severity per cold episode
								Subjective symptom severity per day while sick

C = control; I = intervention; Max, maximum; Min, minimum; NR = not reported.

Age range.

^†

Median age.

^‡

Elemental zinc content.