The Effects of a Healthy Diet on Asthma and Wheezing in Children and Adolescents: A Systematic Review and Meta-Analysis

Figures & data

Figure 1 Flow chart of articles retrieved, screened and included in this meta-analysis.

Figure 2 (A) Overall analysis of a healthy diet and childhood asthma risk in cross-sectional studies. (B) a healthy diet and childhood wheeze risk in cross-sectional studies. (C) an unhealthy diet and childhood asthma risk in cross-sectional studies. (D) an unhealthy diet and childhood wheeze risk in cross-sectional studies. (E) a healthy diet and childhood asthma risk in cohort studies.

Table 1 Overall and Subgroup Analyses of Diet Pattern with Asthma/Wheeze of Children and Adolescents in the Cross-Sectional Studies

Group	Number of Qualified Observations	Asthma			Wheeze
		OR (95% CI); P	I^2	Tau^2	OR (95% CI); P	I^2	Tau^2
Overall analyses
Unhealthy diet (unadjusted)	20/19	1.28 (1.20–1.36); <0.001	50.4%	0.006	0.99 (0.88–1.13); 0.916	81.4%	0.050
Unhealthy diet (adjusted)	70/44	1.21 (1.15–1.28); <0.001	64.9%	0.019	1.09 (1.03–1.16);.006	75.2%	0.023
Healthy diet (unadjusted)	20/20	0.70 (0.58–0.85); <0.001	72.2%	0.113	0.83 (0.72–0.96); 0.010	72.4%	0.071
Healthy diet (adjusted)	85/60	0.85 (0.80–0.89); <0.001	69.8%	0.026	0.85 (0.81–0.89); <0.001	66.8%	0.015
Subgroup analyses based on adjusted healthy diet
By region
Europe	44/25	0.83 (0.77–0.89); <0.001	62.3%	0.025	0.79 (0.74–0.84); <0.001	25.0%	0.005
Oceania	2/2	0.40 (0.21–0.77); 0.006	8.2%	0.020	0.72 (0.42–1.22); 0.216	0.0%	0.000
Asian	19/13	0.98 (0.91–1.06);.626	71.4%	0.012	0.92 (0.87–0.97); 0.003	73.3%	0.006
South America	14/16	0.75 (0.62–0.90);.002	68.4%	0.075	0.87 (0.75–1.01); 0.069	72.6%	0.069
North America	5/3	0.63 (0.47–0.83);.001	31.6%	0.032	0.71 (0.59–0.84); <0.001	0.0%	0.000
By age
Preschool-age children	*/2	*;.*	*	*	0.79 (0.69–0.89); <0.001	67.5%	0.016
School-age children	63/57	0.84 (0.79–0.89); <0.001	70.2%	0.023	0.85 (0.81–0.89); <0.001	0.0%	0.000
Teenagers	12/*	0.91 (0.78–1.05); 0.198	69.3%	0.039	*; *	*	*
Z-test		School-age VS Teenagers	P=0.163		Preschool-age VS School-age	P=0.146
By gender
Boys	3/1	0.97 (0.91–1.05); 0.475	0.0%	0.000	0.74 (0.62–0.89); 0.001	*	0.000
Girls	3/1	1.01 (0.82–1.25); 0.916	56.0%	0.199	0.70 (0.56–0.88); 0.003	*	0.000
By diet frequency
Low	11/9	0.81 (0.70–0.94); 0.007	71.3%	0.033	0.85 (0.72–1.01); 0.068	74.3%	0.049
High	33/26	0.80 (0.71–0.89); <0.001	73.4%	0.062	0.78 (0.72–0.85); <0.001	47.6%	0.020
Z-test		Low VS High	P=0.448		Low VS High	P=0.186
By type of food
Fruit	21/21	0.86 (0.78–0.95); 0.003	58.4%	0.023	0.80 (0.76–0.84); <0.001	32.3%	0.004
Vegetables	19/13	0.91 (0.81–1.02); 0.110	68.9%	0.032	0.93 (0.85–1.01); 0.096	53.9%	0.010
Dairy products	24/15	0.90 (0.81–1.01); 0.065	79.4%	0.044	0.94 (0.87–1.01); 0.104	60.6%	0.011
Sea food	16/13	0.76 (0.65–0.89); 0.001	77.1%	0.048	0.88 (0.78–0.98); 0.019	68.1%	0.019
Cereals	6/4	0.63 (0.40–1.00); 0.049	87.9%	0.283	0.98 (0.90–1.06); 0.566	0.0%	0.000
Nuts	6/5	0.93 (0.82–1.06); 0.292	40.5%	0.001	0.90 (0.83–0.98); 0.011	11.8%	0.001
Protein foods	29/14	1.03 (0.93–1.13); 0.597	77.7%	0.035	1.06 (0.96–1.17); 0.100	94.8%	0.324
Starchy foods	8/13	0.85 (0.63–1.14); 0.285	73.4%	0.123	0.86 (0.76–0.97); 0.015	79.1%	0.032
Mediterranean diet	12/1	0.88 (0.79–0.97); 0.014	63.2%	0.015	0.64 (0.47–0.87); 0.004	*	0.000
Subgroup analyses based on adjusted unhealthy diet
By region
Europe	31/10	1.09 (0.95–1.26); 0.207	59.9%	0.072	1.20 (0.96–1.50); 0.100	52.3%	0.061
Oceania	2/2	1.26 (0.97–1.63); 0.082	0.0%	0.000	1.51 (1.18–1.94); 0.001	0.0%	0.000
Asian	12/8	1.51 (1.22–1.88); <0.001	83.5%	0.093	0.99 (0.93–1.05); 0.699	45.7%	0.003
South America	11/14	1.18 (1.08–1.28); <0.001	65.9%	0.006	1.00 (0.89–1.14); 0.961	77.2%	0.034
North America	7/3	1.49 (1.26–1.76); <0.001	23.6%	0.012	1.52 (0.95–2.44); 0.081	64.9%	0.110
Africa	2/2	1.19 (0.92–1.54); 0.199	40.6%	0.014	1.32 (0.91–1.92); 0.150	80.8%	0.060
International	5/5	1.17 (1.09–1.26); <0.001	11.1%	0.001	1.08 (1.00–1.17); 0.051	0.0%	0.000
By age
School-age children	43/36	1.22 (1.09–1.36); <0.001	66.6%	0.063	1.07 (0.99–1.15); 0.073	66.0%	0.023
Teenagers	14/*	1.21 (1.13–1.29); 0.001	60.6%	0.023	*; *	*	*
Z-test		School-age VS Teenagers	P=0.450		*	*
By gender
Boys	1/*	2.06 (1.29–3.30); 0.003	*	0.000	*; *	*	*
Girls	1/*	1.32 (0.78–2.23); 0.300	*	0.000	*; *	*	*
By diet frequency
Low	12/8	1.10 (0.92–1.31); 0.322	67.2%	0.071	1.00 (0.85–1.17); 0.979	55.6%	0.027
High	32/19	1.26 (1.17–1.36); <0.001	64.9%	0.014	1.21 (1.09–1.35); <0.001	70.1%	0.027
Z-test		Low VS High	P=0.08		Low VS High	P=0.03
By type of food
Fast food	26/11	1.38 (1.26–1.50); <0.001	66.4%	0.018	1.33 (1.18–1.49); <0.001	71.2%	0.020
Margarine	8/5	1.23 (1.13–1.35); <0.001	0.0%	0.000	1.01 (0.87–1.17); 0.930	48.4%	0.013

Note: *Data are not available.

Abbreviations: OR, odds ratio; 95% CI, 95% confidence interval.

Table 2 Overall and Subgroup Analyses of Diet Pattern with Asthma/Wheeze of Children and Adolescents in the Cohort Studies

Group	Number of Qualified Observations	Asthma			Wheeze
		RR (95% CI); P	I^2	Tau^2	RR (95% CI); P	I^2	Tau^2
Overall analyses
Unhealthy diet (adjusted)	7/7	1.00 (0.93–1.08); 0.971	7.6%	0.001	1.03 (0.96–1.12);.385	0.0%	0.000
Healthy diet (adjusted)	6/11	0.91 (0.76–1.09); 0.302	75.8%	0.030	0.72 (0.58–0.90); 0.003	83.5%	0.105
Subgroup analyses based on adjusted healthy diet
By region
Europe	3/7	0.68 (0.54–0.87); 0.002	0.0%	0.000	0.58 (0.50–0.67); <0.001	0.0%	0.000
Oceania	3/4	1.05 (0.88–1.25); 0.626	80.3%	0.019	1.04 (0.83–1.30); 0.752	75.9%	0.037
By age
Preschool-age children	4/4	1.02 (0.87–1.19); 0.842	72.3%	0.017	1.01 (0.79–1.30); 0.944	81.7%	0.050
School-age children	2/6	0.60 (0.44–0.81); 0.001	0.0%	0.000	0.58 (0.49–0.68); <0.001	0.0%	0.000
Z-test		Preschool-age VS School-age	P=0.001		Preschool-age VS School-age	P<0.001
By gender
Boys	*/1	*; *	*	*	0.54 (0.36–0.84); 0.004	*	0.000
Girls	*/1	*; *	*	*	0.53 (0.30–0.92); 0.025	*	0.000
By diet frequency
Low	*/1	*; *	*	*	0.48 (0.31–0.73); 0.068	*	0.000
Moderate	*/1	*; *	*	*	0.61 (0.42–0.89); <0.001	*	0.000
High	*/3	*; *	*	*	0.54 (0.41–0.70); <0.001	0.0%	0.000
By type of food
Sea food	4/4	0.80 (0.55–1.18); 0.260	77.6%	0.115	0.77 (0.53–1.11); 0.162	80.8%	0.118
Fruit	1/6	0.90 (0.82–0.99); 0.028	*	0.000	0.61 (0.45–0.84); 0.003	79.9%	0.119
Vegetables	1/1	1.10 (0.98–1.24); 0.112	*	0.000	1.22 (1.04–1.43); 0.017	*	0.000
Starchy foods	2/2	0.79 (0.51–1.23); 0.302	74.9%	0.079	0.93 (0.81–1.07); 0.300	0.0%	0.000
Dairy products	3/3	0.97 (0.88–1.08); 0.605	0.0%	0.000	0.91 (0.66–1.27); 0.585	81.4%	0.064
Subgroup analyses based on adjusted unhealthy diet
By region
Europe	5/5	0.97 (0.67–1.41); 0.876	36.5%	0.066	1.09 (0.89–1.34); 0.418	0.0%	0.000
Oceania	2/2	1.00 (0.94–1.07); 0.935	0.0%	0.000	1.03 (0.95–1.11); 0.539	0.0%	0.000
By age
Preschool-age children	4/4	1.00 (0.94–1.06); 0.934	0.0%	0.000	1.02 (0.95–1.11); 551	0.0%	0.000
School-age children	3/3	1.14 (0.61–2.14); 0.676	58.7%	0.181	1.28 (0.90–1.82); 0.177	0.0%	0.000
By diet frequency
High	5/5	0.97 (0.67–1.41); 0.876	36.5%	0.066	1.09 (0.89–1.34); 0.418	0.0%	0.000
By type of food
Margarine	2/2	1.00 (0.93–1.09); 0.919	0.0%	0.000	1.00 (0.91–1.11); 0.931	0.0%	0.000
Butter	2/2	0.99 (0.89–1.10); 0.785	0.0%	0.000	1.06 (0.93–1.19); 0.397	0.0%	0.000

Note: *Data are not available.

Abbreviations: RR, risk ratio; 95% CI, 95% confidence interval.

Figure 3 (A) Begg’s funnel plot of healthy diet with asthma in cross-section studies. (B) Filled funnel plot of healthy diet with asthma in cross-sectional studies. (C) Begg’s funnel plot of healthy diet with wheeze in cross-sectional studies. (D) Filled funnel plot of healthy diet with wheeze in cross-sectional studies. (E) Begg’s funnel plot of unhealthy diet with asthma in cross-sectional studies. (F) Begg’s funnel plot of unhealthy diet with wheeze in cross-sectional studies. (G) Begg’s funnel plot of unhealthy diet with wheeze in cohort studies.