Table 2.

Characteristics of the analyzed systematic reviews.

First Author, Year, Country	Type of Review; Number of Eligible Studies Included/Total Number of Studies Included in the Review Designs of Eligible Studies	Total sample Size of Eligible Studies Included/Total Sample Size of all Studies Included in the Review; Age Range and Countries of Participants of Included Studies	Adherence to the MD and Outcome Measures (Method of Assessment)	Assessment of Mediterranean Diet Adherence	Overall Results	Strengths of the Reviews	Limitations of the Reviews
Bujtor et al. [26] 2021 Australia, Spain, UK	Type of review: systematic review 10/53 included studies: 10 observational studies	Sample size = 5661/51,556 Age = 6.5–18 y Countries = Colombia, Portugal, Austria, Belgium, France, Germany, Greece, Hungary, Italy, Spain, Sweden, USA, Turkey	Inflammation markers: CRP, TNF-alpha, IL-1, IL-2, IL-6, TGF-Beta1, sVCAM1, IL-4, IL-17, IL-33	KIDMED; m-KIDMED; MDS; m-MDS; ad hoc score	MD and CRP Inverse significant association: 2 studies (only 1 in females) Direct significant association: 1 study (only in males) Non-significant association: 6 studies (1 in DMT1 patients and 3 in obese/overweight patients) MD and IL-1 Inverse significant association: 1 study Non-significant association: 1 study MD and IL-2 Inverse significant association: 1 study Non-significant association: 1 study MD and IL-6 Inverse significant association: 1 study Non-significant association: 3 studies (1 in DMT1 patients) MD and TNF-alpha Inverse significant association: 1 study Non-significant association: 3 studies MD and TGF-Beta1 Direct significant association: 1 study (only in males) MD and sVCAM1 Inverse significant association: 1 study MD and IL-4 Inverse significant association: 1 study Non-significant association: 2 studies MD and IL-17 Inverse significant association: 1 study MD and IL-33 Direct significant association: 1 study (only in asthmatics)	Adequate adherence to MD in healthy populations results in decreased levels of pro-inflammatory biomarkers	Heterogeneity of studies in terms of sample size, age of participants, biological markers considered, index for assessing MD adherence, health status of the populations Studies do not consider the biological effect of food (intake versus absorption) Currently no consensus regarding the inflammatory biomarkers best used to represent chronic low-grade inflammation in children and adolescents Biomarker measurement errors, such as sampling, storage, and laboratory errors, cannot be excluded
Eslami et al. [31] 2020 Iran	Type of study: systematic review 5/11 included studies: 5 cross-sectional	Sample size = 180,898/198,271 Age = 8–18 y Countries = Spain, Iceland, Chile, Greece	PF (20 m—SRT (stages); 20 m—SRT (VO2 max))	KIDMED	MD and PF Direct significant association: 5 studies	Eligible studies showed that MD adherence was directly associated with CRF improvement	Study designs (all cross-sectional) Did not control for major potential confounding factors (PA and total energy intake) Most studies were conducted with populations living in developed or high-income countries
García-Hermoso et al. [27] 2022 Spain, Chile	Type of review: systematic review with meta-analysis 39/39 included studies: 37 cross-sectional 2, longitudinal (only data from baseline)	Sample size = 565,421/565,421 Age = 6–19 y Countries = Chile, Colombia, Israel, Portugal, Spain, Greece, Iceland, Estonia, Italy, Lithuania, Croatia, Serbia	PA (instrument, i.e., actigraph, questionnaire) SB (screen media time or frequency; sitting time): PF: CRF, muscular fitness, speed—agility (Eurofit Battery, Alpha-Fitness Battery)	KIDMED	MD and PA (r = 0.14; 95% CI 0,11, 0,17; I2 88.6) MD and CRF (r = 0.22; 95% CI 0.13, 0.31; I2 95.7) MD and muscular fitness (r = 0.11; 95% CI 0.03, 0.18; I2 95.4) MD and speed—agility (r = –0.06; 95% CI –0.12, –0.01; I2 84.2) MD and SB (r = –0.15; 95% CI –0.20, –0.10; I2 97.3) MD and SB in children (r = –0.21; 95% CI –0.29, –0.12; I2 96.5) MD and CRF in adolescents (r = 0.30; 95% CI 0.12, 0.47; I2 96.5)	Weak-to-moderate direct relationships between MD adherence and PA, CRF, and muscular fitness Weak-to-moderate inverse relationship between MD adherence and SB and speed—agility Youths with higher adherence to the MD were more likely to be physically active and fit and have a less sedentary lifestyle	Heterogeneity between studies in the associations, exposure, outcomes assessment, and publication bias Study designs (cross-sectional) Most of the studies did not consider potential confounding factors, such as socio-economic status and/or parental education
Garcia-Marcos et al. 2013 [24] Spain, Chile, Germany, Greece	Type of study: systematic review with meta-analysis 7/8 included studies: 7 cross-sectional	Sample size = 38,047/39,804 Age = 6–18 y Countries = Spain, Mexico, Albania, China, Ecuador, Estonia, France, Georgia, Germany, Ghana, Greece, India, Italy, Latvia, The Netherlands, New Zealand, Norway, Sweden, Turkey, UK, West Bank	Asthma: current wheeze (CW), current severe wheeze (CSW), asthma ever (AE) (wheeze episodes survey)	KIDMED; MDS; m-MDS	MD and CW OR: 0.85; 95% CI 0.75–0.98; p = 0.02 Mediterranean centers: OR: 0.79; 95% CI 0.66–0.94; p = 0.009 Non-Mediterranean centers: OR: 0.91; 95% CI 0.78–1.05; p = NS MD vs. non-MD centers: Q = 1.38; p = NS MD and CSW OR: 0.82; 95% CI 0.55–1.22; p = NS Mediterranean centers: OR: 0.66; 95% CI 0.48–0.90; p = 0.008 Non-Mediterranean centers: OR: 0.99; 95% CI 0.79–1.25; p = NS MD vs. non-MD centers: Q: 4.33; p = 0.037 MD and AE OR: 0.86; 95% CI 0.78–0.95; p = 0.004 Non-Mediterranean centers: OR: 0.86; 95% CI 0.75–0.98; p = 0.027 Mediterranean centers: OR: 0.86; 95% CI 0.74–1.01; p = NS MD vs. non-MD regions: Q = 0.001; p = NS	Adherence to the MD is a protective factor for CW, SCW, and AE specifically for Mediterranean centers	Heterogeneity in adherence to the MD assessment Study designs (all studies were cross-sectional) The use of the highest vs. the lowest tertile instead of a different approach, such as using the median as a cut-off point, probably minimized the effect of the different scoring systems across studies
Iaccarino et al. [33] 2017 Italy	Type of study: systematic review 25/58 included studies: 23 cross-sectional, 2 longitudinal	Sample size = 51,781/137,846 Age = 6–19 y Countries = Spain, Italy, Greece, UK, Cyprus, Portugal, Ireland	Anthropometric variables/body composition: BMI, WC, BF PA (questionnaires, accelerometers) SB (media screen time) PF (20 m Shuttle Run test)	KIDMED; m-KIDMED; MDS; m-MDS	MD and BMI Inverse significant association: 8 studies Direct significant association: 1 study Non-significant association: 12 studies 2 prospective studies found no longitudinal relationship MD and WC Inverse significant association: 2 studies Direct significant association: 1 study Non-significant association: 4 studies MD and BF Non-significant association: 5 studies MD and PA Direct significant association: 14 studies Non-significant association: 3 studies MD and PF Direct significant association: 1 study MD and SB Inverse significant association: 9 studies Non-significant association: 1 study	Most of the eligible studies showed that MD adherence was directly associated with physical activity and inversely associated with sedentary behavior, while the results for weight status were not consistent	Study designs (most of the studies were cross-sectional) Methodological differences and limitations in the studies included Use of self-reported anthropometric data could have biased the association between MD adherence and weight status
Koumpagioti et al. [28] 2022 Greece	Type of study: systematic Review 7/12 included studies: 5 cross-sectional, 1 case-control, 1 cohort	Sample size = 33,340/34,972 Age = 6–19 y Countries = Turkey, Greece, Peru, Lebanon, France	Asthma (spirometry): physician-diagnosed asthma, ever asthma symptoms, current asthma, asthma control, FEV1, FVC, Fractional Exhaled Nitric Oxide (FeNO) Allergies: physician-diagnosed allergic rhinitis, lifetime rhinitis, current rhinoconjunctivitis, atopic status, current eczema	KIDMED; MDS; m-MDS	MD and asthma Inverse significant association: 4 studies Non-significant association: 1 study MD and allergies Non-significant association: 4 studies	Adherence to the MD seemed to have a protective role against childhood asthma, but no effect was found on allergic rhinitis, eczema, or atopy	Heterogeneity among the included studies in the designs, sample sizes, tools assessing MD adherence, participants’ ages, variable outcomes, and adjusted confounders Study designs (most of the studies were cross-sectional)
Lassale et al. [29] 2021 Spain	Type of study: systematic review 45/55 included studies: 6 RCTs, 36 cross-sectional, 3 longitudinal	Sample size = 234,236/601,740 Age: = 6–19 y Countries = Spain, Italy, Greece, Mexico, Israel, Chile, Colombia, Croatia, Lebanon, Estonia, Iceland, Iran, Lithuania, Serbia, USA, Finland, Turkey, UK	Anthropometric variables: BMI, WHtR, WC, general and abdominal obesity, BF	KIDMED; m-KIDMED; m-MDS; MediLIFE Index; Krece plus test	MD and obesity Intervention studies: Before/after comparisons: significant reduction: 4 studies With control group comparisons: Significant differences: 2 studies Non-significant differences: 2 studies Observational studies: General adiposity: Non-significant association: 25 studies Inverse association: 14 studies Abdominal adiposity: Non-significant association: 7 studies Inverse association: 2 studies	Most of the eligible studies showed limited evidence for the MD and obesity	Only one of these studies was of high quality and included paternal educational level as a potential confounder in the analysis Low quality of the included studies Heterogeneity in the adherence to the MD assessment Study design (most of the studies were cross-sectional)
Lv et al. [30] 2014 USA	Type of study: systematic review 10/31 included studies: 9 cross-sectional, 1 cohort	Sample size = 90,102/518,782 Age = 6–18 y Countries = Greece, Spain, Mexico, Ecuador, Estonia, France, Georgia, Germany, Ghana, Iceland, India, Italy, Latvia, New Zealand, Norway, Sweden, Turkey, UK	Asthma: asthma symptoms, current severe asthma, ever asthma, prevalence and severity of ever asthma, current occasional asthma, clinically significant asthma, ever wheeze, current wheeze, atopic wheeze, persistent wheeze, exercise wheeze, wheezing ever with atopy, lung function (FEV1, FVC), inflammatory response (IL-8)	KIDMED: m-KIDMED; MDS; m-MDS; ad hoc score	MD and asthma Inverse significant association: 7 studies Non-significant association: 3 studies	Higher adherence to the Mediterranean Diet may be associated with reduced asthma risk in children	Study designs (most of the studies were cross-sectional) Heterogeneity in MD adherence assessment and in asthma outcomes
Papamichael et al. [32] 2017 Australia	Type of study: systematic review 12/15 included studies: 9 cross-sectional, 1 case-control, 2 longitudinal (only baseline)	Sample size = 100,968/103,248 Age = 6–19 y Countries = Spain, Greece, Mexico, Turkey, Peru, Brazil, Albania, China, Ecuador, Estonia, France, Georgia, Germany, Ghana, India, Italy, Latvia, The Netherlands, New Zealand, Norway, Spain, Sweden, UK, West Bank	Asthma: (ISAAC respiratory questionnaire; spirometry): current asthma, ever asthma, overall lifetime prevalence of asthma, any asthma symptoms, current severe asthma (CSA), current occasional asthma (COA), doctor-diagnosed asthma, severe asthma, exercise-induced asthma, asthma control, night cough, BHR (hyper-responsiveness), FEV1, IL-8, FVC, exhaled nitric oxide level (eNO), exhaled breath condensate (EBC), ever wheeze, ever diagnosed wheeze, exercise wheeze, wheeze limiting speech, wheeze disturbing sleep, current wheeze, wheezing ever with atopy, wheeze in last 12 months, severe attacks of wheeze, persistent wheeze, atopic wheeze, atopy	KIDMED, MDS, m-MDS	MD and asthma Inverse significant association: 8 studies Inverse non-significant association: 2 studies Non-significant association: 1 study Direct significant association: 1 study	Adherence to the Mediterranean dietary pattern may reduce asthma symptoms in children (limited evidence)	Heterogeneity in study methodologies, age of participants, and sample size The majority of studies were cross-sectional
Romero Robles et al. [24] 2022 Peru	Type of study: systematic review 9/11 included studies: 9 cross-sectional	Sample size = 4654/6796 Age = 8–18 y Countries = Spain, Greece, Portugal, Lebanon, Italy	Health-related quality of life (KIDSCREEN-10, KIDSCREEN-27, KIDSCREEN-52, Peds-Ql)	KIDMED	MD and HRQoL general score Direct significant association: 5 studies Direct non-significant association: 2 studies Inverse non-significant association: 1 study MD and HRQoL subdomains All dimensions Direct significant association: 1 study Physical well-being and peers and school environment subdomain Direct significant association: 1 study	Positive correlation between adherence to the MD and HRQoL	Study designs (all studies were cross-sectional) Heterogeneity of the measurements used for HRQoL
Teixeira et al. [25] 2022 Portugal	Type of review: systematic review 23/128 included studies: 18 cross-sectional, 1 RCT, 1 case-control, 3 cohort longitudinal	Sample size = 34,266/329,898 Age = 6–17 y Countries = Italy, Spain, Portugal, Turkey, Chile, Greece, Colombia, Morocco, Germany, Austria, Belgium, France, Hungary, Sweden, UK, England	Anthropometric variables/body composition: BMI, WC, BF, skinfold thickness, neck circumference Clinical markers: albuminuria, blood pressure, C-RP, bone mineral density Asthma (symptoms) ADHD (diagnosis) Depression, night eating syndrome	KIDMED; m-KIDMED; MDS; m-MDS	MD and BMI Intervention studies: Inverse significant association: 1 study Observational studies: Inverse significant association: 6 studies Direct significant association: 1 study Non-significant association: 8 studies MD and WC Inverse significant association: 4 studies Direct significant association: 1 study Non-significant association: 1 study MD and BF Inverse significant association: 2 studies MD and subscapular skinfold thickness Inverse significant association: 1 study MD and neck circumference Inverse significant association: 1 study MD and albuminuria Inverse non-significant association: 1 study MD and blood Pressure: Inverse significant association: 1 study Direct significant association: 1 study Non-significant association: 1 study MD and C-RP Inverse significant association: 1 study MD and bone mineral density Direct significant association: 1 study MD and asthma Inverse significant association: 1 study MD and ADHD Inverse significant association: 1 study MD and depression Non-significant association: 1 study MD and night eating syndrome Non-significant association: 1 study	Inconsistent association between MD adherence and BMI Potential significant association between MD adherence and anthropometric variables that needs to be further investigated; the evidence is still scarce	Different characteristics of studies in terms of sample size, age of participants, outcomes assessment, method of food intake consumption Study designs (most of the studies were cross-sectional)

Abbreviations: MD = Mediterranean Diet; PA = physical activity; SB = sedentary behavior; CRF = cardiorespiratory fitness; PF = physical fitness; BMI= body mass index; WC = waist circumference; ST = skinfold thickness; BF= body fat; WHtR = waist to height ratio; CRP = C-reactive protein; FEV1 = Forced Expiratory Volume in 1 s; FVC = Forced Vital Capacity; KIDMED = Mediterranean Diet Quality Index for children and adolescents; m-KIDMED = KIDMED index modified; MDS = Mediterranean Diet Score; m-MDS = Mediterranean Diet Score modified; MediLIFE Index = Mediterranean lifestyle index.