Organic Diet Intervention in Primary School Children (ORGANIKO)

The study aims to evaluate the hypothesized benefits of a systematic organic diet for children, over those of a conventional diet. The specific objectives of this study are to: i) Demonstrate the decreased body burden of pesticides for those children consuming an organic diet, and ii) Evaluate the effects in specific biomarkers of inflammation and oxidative stress in children systematically consuming an organic diet.

A single-blinded, randomised 2 x 2 cross-over study is conducted to evaluate the effect of a 40-day organic diet compared to a 40-day conventional diet on biomarkers of exposure (pesticides metabolites) and biomarkers of effect (oxidative stress/inflammation markers) in children. The study is approved by the Cyprus National Bioethics Committee (ΕΕΒΚ/ΕΠ/2016/25) and the Cyprus Ministry of Education and Culture (7.15.06.15/2). Written informed consent for children to participate in the study is obtained from children's parents or legal guardians. Study participants are recruited from public primary schools in Limassol, Cyprus following communication with the school's headmaster. Each school that participates in the study is randomized to one of the two study arms; conventional-organic or organic-conventional. Participants' blinding is not possible since children know which diet they have at each phase. However, all documents and urine containers are coded, so that researchers are blinded to subjects' identity and group allocation. Participants provide 6 first morning urine samples during the duration of the study; 1 baseline sample, 2 samples in the conventional phase and 3 samples in the organic phase. Anthropometric measurements (weight, height, waist circumference) are taken at the beginning and end of the study by trained researchers at the school area. A baseline questionnaire is administered to parents at the beginning of the study through a telephone interview to collect information on demographic characteristics, pesticide use at household and children's activities. A food frequency questionnaire is administered to parents at the end of the conventional phase through a telephone interview to collect information about the food habits of the children during the 40-day conventional period. A food diary is given to parents at the beginning of the study and parents use it during the organic phase, to collect information about the compliance of the children to the organic dietary menu, the children's health status and the pesticide use at home. In order to encourage adherence to the organic diet menu, an event is organised during the organic phase of both groups, with activities for children and free sampling of organic food products. Descriptive statistics are used to summarize the demographic characteristics for participating children. Categorical variables are described as sample size and percentages, normally-distributed continuous variables as mean±SD and non-normal continuous variables as median and interquartile range (Q1-Q3) or the appropriate transformation is conducted, such as the log transformation. For testing whether characteristics of interest are different among groups the Student's t-test are utilized for continuous normally distributed variables and the chi-square test for categorical characteristics. For continuous data that are not normally distributed, the Wilcoxon non-parametric analysis is used instead or a transformation of the data is conducted first in order to meet the normality criterion. Linear mixed-effects models are used to account for the correlation among repeat urine samples collected from the same child and determine whether mean pesticide metabolite and biomarkers concentrations differ between the organic phase and the conventional phase.

During the conventional phase, participants are asked to maintain their usual dietary choices for 40 days.

During the organic phase, participants are asked to follow strictly the two 20-day organic dietary menus provided to them for 40 days. The organic dietary menus were prepared by a certified dietitian. The meals of the organic phase are prepared by a certified organic restaurant and are delivered to school every day except Sunday. For the meals of breakfast and afternoon snacks, children choose their preferred options for the week on the Friday of the previous week according to a list of organic food items and the products for these meals are delivered on Saturday along with the rest meals. Parents are responsible to pick-up the organic meals from school and ensure that the participating children have access to them.

Full organic diet from certified organic products as obtained from certified producers and cooked by a certified organic restaurant. five meals each day delivered to students.

Change in Pesticide Metabolite 3-phenoxybenzoic Acid (3-PBA) Levels in Urine Between Organic and Conventional Periods*

Percent change in pesticide metabolite 3-phenoxybenzoic acid (3-PBA) levels between the last sample of the conventional treatment period (before the start of the organic treatment) and the last sample of organic treatment period. A one-sample t-test was used to assess whether the percent change was different than zero. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

Last sample of the conventional period and the last sample of organic period, up to 40 days for each period

Overall difference in median 3-PBA levels between the conventional and organic periods. The overall differences in the medians of biomarkers between the conventional and the organic phase were assessed with the non-parametric Wilcoxon rank sum test on the creatinine-adjusted concentrations pooling all conventional samples (including the baseline) and the organic samples for all participants, regardless of the duration for which they followed the organic treatment. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Effect of Organic Treatment in 3-PBA Levels in Urine, Taking in Account the Repeated Measures and Duration of Organic Period

A linear mixed-effect regression model was fitted for 3-PBA (log-transformed, creatinine-adjusted). The model accounted for the duration and the effect of treatment. It included student-level (repeated measures within person) and school-level (multiple students clustered within each school) random intercepts with an unstructured covariance matrix. Continuous variables, other than time (days of treatment), were centered at the population means. The model included fixed effects for treatment condition (organic or conventional) and time (days of treatment), where time = 0 was used for the start of the treatment. The model was adjusted for the baseline value (first urine sample for all children) of the outcome to account for the background participant levels. An interaction term for time and treatment was considered and subsequently dropped if it did not meet the threshold of p-value<0. 05.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Overall Difference in Median 6-chloronicotininc Acid (6-CN) Levels in Urine Between the Conventional and Organic Periods*

Overall difference in median 6-CN levels between the conventional and organic periods. The overall differences in the medians of biomarkers between the conventional and the organic phase were assessed with the non-parametric Wilcoxon rank sum test on the creatinine-adjusted concentrations pooling all conventional samples (including the baseline) and the organic samples for all participants, regardless of the duration for which they followed the organic treatment. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Effect of Organic Treatment in 6-CN Levels in Urine, Taking in Account the Repeated Measures and Duration of Organic Period - Odds Ratio Calculated Based on the Fit of a Logistic Mixed-effect Model

A logistic model was fitted for 6-CN (binary variable; above and below LOD) due to the high number of values below LOD. The model accounted for the duration and the effect of treatment. It included student-level (repeated measures within person) and school-level (multiple students clustered within each school) random intercepts with an unstructured covariance matrix. Continuous variables, other than time (days of treatment), were centered at the population means. The model included fixed effects for treatment condition (organic or conventional) and time (days of treatment), where time = 0 was used for the start of the treatment. The model was adjusted for the baseline value (first urine sample for all children) of the outcome to account for the background participant levels. An interaction term for time and treatment was considered and subsequently dropped if it did not meet the threshold of p-value<0. 05.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Change in Oxidative Stress/Inflammation Biomarker 8-OHdG Levels in Urine Between Organic and Conventional Periods*

Percent change in oxidative stress/inflammation biomarker 8-OHdG levels between the last sample of the conventional treatment period (before the start of the organic treatment) and the last sample of organic treatment period. A one-sample t-test was used to assess whether the percent change was different than zero. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

Last sample of the conventional period and the last sample of organic period, up to 40 days for each period

Overall difference in median 8-OHdG levels between the conventional and organic periods. The overall differences in the medians of biomarkers between the conventional and the organic phase were assessed with the non-parametric Wilcoxon rank sum test on the creatinine-adjusted concentrations pooling all conventional samples (including the baseline) and the organic samples for all participants, regardless of the duration for which they followed the organic treatment. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Effect of Organic Treatment in 8-OHdG Levels in Urine, Taking in Account the Repeated Measures and Duration of Organic Period

A linear mixed-effect regression model was fitted for 8-OHdG (log-transformed, creatinine-adjusted). The model accounted for the duration and the effect of treatment. It included student-level (repeated measures within person) and school-level (multiple students clustered within each school) random intercepts with an unstructured covariance matrix. Continuous variables, other than time (days of treatment), were centered at the population means. The model included fixed effects for treatment condition (organic or conventional) and time (days of treatment), where time = 0 was used for the start of the treatment. The model was adjusted for the baseline value (first urine sample for all children) of the outcome to account for the background participant levels. An interaction term for time and treatment was considered and subsequently dropped if it did not meet the threshold of p-value<0. 05.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Change in Oxidative Stress/Inflammation Biomarker 8-iso-PGF2a Levels in Urine Between Organic and Conventional Periods*

Percent change in oxidative stress/inflammation biomarker 8-iso-PGF2a levels between the last sample of the conventional treatment period (before the start of the organic treatment) and the last sample of organic treatment period. A one-sample t-test was used to assess whether the percent change was different than zero. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

Last sample of the conventional period and the last sample of organic period, up to 40 days for each period

Overall Difference in Median 8-iso-PGF2a Levels in Urine Between the Conventional and Organic Periods*

Overall difference in median 8-iso-PGF2a levels between the conventional and organic periods. The overall differences in the medians of biomarkers between the conventional and the organic phase were assessed with the non-parametric Wilcoxon rank sum test on the creatinine-adjusted concentrations pooling all conventional samples (including the baseline) and the organic samples for all participants, regardless of the duration for which they followed the organic treatment. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Effect of Organic Treatment in 8-iso-PGF2a Levels in Urine, Taking in Account the Repeated Measures and Duration of Organic Period

A linear mixed-effect regression model was fitted for 8-iso-PGF2a (log-transformed, creatinine-adjusted). The model accounted for the duration and the effect of treatment. It included student-level (repeated measures within person) and school-level (multiple students clustered within each school) random intercepts with an unstructured covariance matrix. Continuous variables, other than time (days of treatment), were centered at the population means. The model included fixed effects for treatment condition (organic or conventional) and time (days of treatment), where time = 0 was used for the start of the treatment. The model was adjusted for the baseline value (first urine sample for all children) of the outcome to account for the background participant levels. An interaction term for time and treatment was considered and subsequently dropped if it did not meet the threshold of p-value<0. 05.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Change in Oxidative Stress/Inflammation Biomarker MDA Levels in Urine Between Organic and Conventional Periods*

Percent change in oxidative stress/inflammation biomarker MDA levels between the last sample of the conventional treatment period (before the start of the organic treatment) and the last sample of organic treatment period. A one-sample t-test was used to assess whether the percent change was different than zero. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

Last sample of the conventional period and the last sample of organic period, up to 40 days for each period

Overall difference in median MDA levels between the conventional and organic periods. The overall differences in the medians of biomarkers between the conventional and the organic phase were assessed with the non-parametric Wilcoxon rank sum test on the creatinine-adjusted concentrations pooling all conventional samples (including the baseline) and the organic samples for all participants, regardless of the duration for which they followed the organic treatment. *Note: This test does not take into account the repeated measures for each participant and the organic treatment duration. The results of the linear-mixed effect models are the ones considered (reported in a section below) as they take into account the repeated measures for each participant and the organic treatment duration.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Effect of Organic Treatment in MDA Levels in Urine, Taking in Account the Repeated Measures and Duration of Organic Period

A linear mixed-effect regression model was fitted for MDA (log-transformed, creatinine-adjusted). The model accounted for the duration and the effect of treatment. It included student-level (repeated measures within person) and school-level (multiple students clustered within each school) random intercepts with an unstructured covariance matrix. Continuous variables, other than time (days of treatment), were centered at the population means. The model included fixed effects for treatment condition (organic or conventional) and time (days of treatment), where time = 0 was used for the start of the treatment. The model was adjusted for the baseline value (first urine sample for all children) of the outcome to account for the background participant levels. An interaction term for time and treatment was considered and subsequently dropped if it did not meet the threshold of p-value<0. 05.

1 baseline sample, 2 samples in the conventional period (typical conventional diet) and 3 samples in the organic period, up to 40 days for each Period

Inclusion Criteria: Healthy children aged 10-12 years, residing in Cyprus over the last five years who consume primarily (> 80%) conventional food (non-organic). Exclusion Criteria: Children with chronic conditions (e.g. diabetes, asthma) or allergies in food (e.g. gluten, lactose tolerance)

Makris KC, Konstantinou C, Andrianou XD, Charisiadis P, Kyriacou A, Gribble MO, Christophi CA. A cluster-randomized crossover trial of organic diet impact on biomarkers of exposure to pesticides and biomarkers of oxidative stress/inflammation in primary school children. PLoS One. 2019 Sep 4;14(9):e0219420. doi: 10.1371/journal.pone.0219420. eCollection 2019.

Konstantinou C, Gaengler S, Oikonomou S, Delplancke T, Charisiadis P, Makris KC. Use of metabolomics in refining the effect of an organic food intervention on biomarkers of exposure to pesticides and biomarkers of oxidative damage in primary school children in Cyprus: A cluster-randomized cross-over trial. Environ Int. 2022 Jan;158:107008. doi: 10.1016/j.envint.2021.107008. Epub 2021 Nov 30.