Potential impacts of synthetic food dyes on activity and attention in children: a review of the human and animal evidence

Miller, Mark D.; Steinmaus, Craig; Golub, Mari S.; Castorina, Rosemary; Thilakartne, Ruwan; Bradman, Asa; Marty, Melanie A.

doi:10.1186/s12940-022-00849-9

Environmental Health

Table 2 Clinical trials of synthetic food dyes and neurobehavioral outcomes in children: summary of study results

From: Potential impacts of synthetic food dyes on activity and attention in children: a review of the human and animal evidence

	Total	No association^a		Association identified^b		Large effect size^b		Statistically significant^b		p^c
Variable	N	N	%	N	%	N	%	N	%	p^c
All studies	25	9	36.0	16	64.0	3	12.0	13	52.0
Group results^d
Parent	14	7	50.0	7	50.0	1	7.1	6	42.9	Ref
Teacher	7	6	85.7	1	14.3	0	0.0	1	14.3	0.11
Other	14	9	64.3	5	35.7	2	14.3	3	21.4	0.45
Individual results^e
Parent	12	3	25.0	9	75.0	4	33.3	5	41.7	Ref
Teacher	2	1	50.0	1	50.0	1	50.0	0	0.0	0.12
Other	5	1	20.0	4	80.0	3	60.0	1	20.0	0.91
Study quality^f
Higher	12	4	33.3	8	66.7	2	16.7	6	50.0	Ref
Lower	13	5	38.5	8	61.5	1	7.7	7	53.8	0.79
Publication year
Before 1990	19	8	42.1	11	57.9	3	15.8	8	42.1	Ref
1990 and later	6	1	16.7	5	83.3	0	0.0	5	83.3	0.26
Location
United States	10	4	40.0	6	60.0	2	20.0	4	40.0	Ref
Elsewhere	15	5	33.3	10	66.7	1	6.7	9	60.0	0.73
In hyperactive only^g
Yes	12	5	41.7	7	58.3	1	8.3	6	50.0	Ref
No	13	4	30.8	9	69.2	2	15.4	7	53.8	0.57
Prior responders only^h
Yes	14	7	50.0	7	50.0	1	7.1	6	42.9	Ref
No	11	2	18.2	9	81.8	2	18.2	7	63.6	0.10
No. of participants
< 20	15	7	46.7	8	53.3	2	13.3	6	40.0	Ref
20–100	7	1	14.3	6	85.7	1	14.3	5	71.4	0.14
≥ 100	3	1	33.3	2	66.7	0	0.0	2	66.7	0.67
RCDP
Yes	16	6	37.5	10	62.5	2	12.5	8	50.0	Ref
No	9	3	33.3	6	66.7	1	11.1	5	55.6	0.83
Challenge agents
Multiple dyes	19	7	36.8	12	63.2	3	15.8	9	47.4	Ref
Tartrazine only	6	2	33.3	4	66.7	0	0.0	4	66.7	0.88
Daily dose (mg)
≤ 10	4	2	50.0	2	50.0	0	0.0	2	50.0	Ref
11–35	7	4	57.1	3	42.9	0	0.0	3	42.9	0.82
36–99	8	2	25.0	6	75.0	2	25.0	4	50.0	0.39
≥ 100+	3	1	33.3	2	66.7	0	0.0	2	66.7	0.66
Unclear	3	0	0.0	3	100.0	1	33.3	2	66.7	0.15
Washout > 2 days
Yes	11	6	54.5	5	45.5	1	9.1	4	36.4	Ref
No	14	3	21.4	11	78.6	2	14.3	9	64.3	0.09
Food dyes only
Yes	22	9	40.9	13	59.1	3	13.6	10	45.5	Ref
Additional agentⁱ	3	0	0.0	3	100.0	0	0.0	3	100.0	0.17
Validated
Yes	17	5	29.4	12	70.6	2	11.8	10	58.8	Ref
No	8	4	50.0	4	50.0	1	12.5	3	37.5	0.32
Outcome timing
Hourly	9	4	44.4	5	55.6	2	22.2	3	33.3	Ref
Daily	6	0	0.0	6	100.0	0	0.0	6	100.0	0.06
Several per week	3	1	33.3	2	66.7	1	33.3	1	33.3	0.74
Weekly	3	1	33.3	2	66.7	0	0.0	2	66.7	0.74
Greater than weekly	1	0	0.0	1	100.0	0	0.0	1	100.0	0.39
Unclear	3	3	100.0	0	0.0	0	0.0	0	0.0	0.09
Full results
Yes	12	5	41.7	7	58.3	2	16.7	5	41.7	Ref
No	13	4	30.8	9	69.2	1	7.7	8	61.5	0.57
Low infractions^j
Yes	16	7	43.8	9	56.3	3	18.8	6	37.5	Ref
No or unknown	9	2	22.2	7	77.8	0	0.0	7	77.8	0.28

Abbreviations: RCDP, studies that are randomized crossover design, double blinded, and placebo controlled; Ref, reference category
Only includes studies involving an active challenge i.e. diet elimination trials were not included in this table
^a Studies that did not report an association that was statistically significant, an effect size ≥20%, or standardized effect size ≥0.20
^b Studies that reported a statistically significant association, an effect size ≥20%, or standardized effect size ≥0.20. This category combines the studies listed under the “Large effect size” and “Statistically significant” columns. The “Statistically significant” column includes any study reporting a statistically significant association, regardless of effect size. The “Large effect size” column includes studies that reported an effect size ≥20% or a standardized effect size ≥0.20 but the results were not statistically significant
^c Chi-square p-value comparing proportion of studies finding no association (i.e. those in the “No association” column) to the proportion of studies finding an association (i.e. those in the “Association identified” column)
^d In studies that presented group means, provides results by the source of the outcome information (Parent, Teacher, or Other). The number of studies listed here is greater than the total number of studies since several studies presented results for more than one outcome source
^e In studies that presented results for individual participants, provides results by the source of the outcome information (Parent, Teacher, or Other). Several studies presented results for more than one outcome source
^f Divides studies by quality scores above (“Higher”) or below (“Lower”) the median score of 10
^g “Yes” if the study only included participants who were previously reported to have some condition related to hyperactivity
^h “Yes” if the study only included participants who were previously reported to have had some behavioral improvements on a synthetic food dye elimination diet
ⁱ Typically a preservative like benzoic acid
^j “Yes” if the average number of dietary infractions was low (e.g., < 2 per week)

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